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Inheritance

1

Autosomal dominant inheritance with age-dependent incomplete penetrance HP:0000006

Cowden syndrome is inherited as an autosomal dominant trait, and each child of an affected individual has a 50% chance of inheriting the variant. Most cases are simplex - no known affected relative - but that is not the same as de novo, and GeneReviews declines to put a number on the split because the condition is underdiagnosed; perhaps 10-50% of individuals have an affected parent. Penetrance is high but incomplete and strongly age-dependent, which is why cumulative lifetime cancer risk is the meaningful risk statement for this entry and a cross-sectional figure is not. Expressivity is variable even within a single family: the same germline PTEN variant can present as isolated macrocephaly with autism in one relative and as early breast or thyroid cancer in another. Sex modifies expression: breast and endometrial risk apply to female carriers, so a single "any cancer" lifetime figure conceals a large difference between sexes.

Autosomal dominant inheritance Penetrance: INCOMPLETE Expressivity: VARIABLE

Show evidence (3 references)

PMID:23335809 SUPPORT Human Clinical

"Cumulative cancer risks at age 70 were 85% (95% CI 70% to 95%) for any cancer, 77% (95% CI 59% to 91%) for female breast cancer, and 38% (95% CI 25% to 56%) for thyroid cancer."

Risks are reported as cumulative to age 70, which is the operational expression of age-dependent penetrance.

PMID:20301661 SUPPORT Other

"Each child of an affected individual has a 50% chance of inheriting the pathogenic variant and developing PHTS."

The GeneReviews transmission-risk statement, which is the baseline this block should carry.

PMID:20301661 SUPPORT Other

"Because CS is likely underdiagnosed, the actual proportion of simplex cases (defined as individuals with no obvious family history) and familial cases (defined as ≥2 related affected individuals) cannot be determined. The majority of CS cases are simplex. Perhaps 10%-50% of individuals with..."

GeneReviews explicitly declines to quantify the simplex/familial split. Quoted at length because the hedge is the substance: an earlier draft of this block asserted that a substantial proportion of cases are de novo, which this source does not support and which conflates simplex with de novo.

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Subtypes

7

Cowden Syndrome 1 (PTEN) MONDO:0008021

PTEN hgnc:9588

Classic Cowden syndrome caused by germline loss-of-function mutations in PTEN on chromosome 10q22-23, accounting for approximately 80% of cases meeting strict clinical diagnostic criteria. Mutations include nonsense, frameshift, missense, splice-site variants, and large deletions. ClinGen grades the PTEN relationship Definitive against PTEN hamartoma tumor syndrome, the lumped entity that includes Cowden syndrome; it is the only one of the seven subtype genes graded above Limited.

Show evidence (2 references)

PMID:24136893 SUPPORT Human Clinical

"Although it was initially reported that approximately 80% of patients with Cowden syndrome had an identifiable germline PTEN mutation, more recent work has shown these diagnostic criteria to be far less specific."

Establishes PTEN mutation as the predominant genetic cause in Cowden syndrome 1, noting that original ~80% frequency estimates derived from clinically ascertained cohorts.

CGGV:assertion_2e9e89c0-8d1b-4276-bd6f-90c7b7190ffb-2024-04-05T170000.000Z SUPPORT Other

ClinGen's Hereditary Cancer expert panel grades the PTEN relationship Definitive, against Limited for AKT1 and no assertion at all for the other five subtype genes.

Cowden Syndrome 2 (SDHB) MONDO:0012878

SDHB hgnc:10681

PTEN-negative Cowden/Cowden-like syndrome associated with germline variants in succinate dehydrogenase subunit B. Three of the ten SDHx carriers in the series that defined this subtype carried an SDHB variant. These variants are better framed as Cowden-like susceptibility alleles than as classic PTEN-defined Cowden syndrome causes: ClinGen has curated SDHB only against hereditary pheochromocytoma-paraganglioma and mitochondrial disease, not against Cowden syndrome. The carriers were selected on raised manganese superoxide dismutase expression as a marker of mitochondrial dysfunction, and in the absence of PTEN alteration their variants raise phospho-AKT and phospho-MAPK.

Show evidence (2 references)

PMID:18678321 SUPPORT Human Clinical

"Among these, 10 (13.5%) had germline mutations/variants in SDHB (n = 3) or SDHD (7), not found in 700 controls (p < 0.001)."

Gives the per-gene carrier counts that separate this SDHB subtype from the SDHD subtype, with the control comparison.

PMID:18678321 SUPPORT Human Clinical

"Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."

Establishes germline SDHx variants as a contributor in Cowden/Cowden-like syndrome in PTEN-mutation-negative individuals with elevated cancer risk.

Cowden Syndrome 3 (SDHD) MONDO:0014045

SDHD hgnc:10683

The SDHD counterpart of CS2, and the larger of the two SDHx arms: seven of the ten SDHx carriers in the defining series carried an SDHD variant. The same caveats apply as for CS2 - the relationship is a PTEN-negative Cowden-like susceptibility rather than a classic Cowden syndrome cause, and ClinGen has curated SDHD only against hereditary pheochromocytoma-paraganglioma and mitochondrial disease.

Show evidence (1 reference)

PMID:18678321 SUPPORT Human Clinical

"Among these, 10 (13.5%) had germline mutations/variants in SDHB (n = 3) or SDHD (7), not found in 700 controls (p < 0.001)."

Reports the seven SDHD carriers that define this subtype, distinct from the three SDHB carriers recorded under CS2.

Cowden Syndrome 4 (KLLN) MONDO:0014046

KLLN hgnc:37212

Cowden syndrome caused by germline epigenetic silencing (promoter hypermethylation) of KILLIN (KLLN), a p53-co-regulated tumor suppressor transcribed from the same bidirectional promoter as PTEN. KLLN methylation down-regulates KILLIN expression and is associated with increased breast and renal cancer risk. This is the one subtype whose lesion is an epimutation rather than a sequence variant, and the authors of the defining study asked for their observations to be replicated.

Show evidence (2 references)

PMID:21177507 SUPPORT Human Clinical

"Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals."

Defines KLLN germline epigenetic silencing as a cause of Cowden/Cowden-like syndrome, conferring higher breast and kidney cancer risk than PTEN mutation alone.

PMID:21177507 SUPPORT Human Clinical

"The germline methylation was found to transcriptionally down-regulate KILLIN by 250-fold"

The measured effect of the epimutation on KILLIN expression, which is the molecular lesion this subtype is defined by.

Cowden Syndrome 5 (PIK3CA) MONDO:0014047

PIK3CA hgnc:8975

PTEN-negative Cowden-like syndrome associated with activating germline variants in PIK3CA, the catalytic subunit of PI3-kinase, reported in 8 of 91 PTEN-negative CS probands. These variants are better framed as Cowden-like susceptibility alleles than as classic PTEN-defined Cowden syndrome causes. Reported variants raise phospho-AKT and cellular PIP3, mimicking PTEN loss at the pathway level. ClinGen has no Cowden assertion for PIK3CA, and grades PIK3CA against hereditary breast carcinoma as Refuted.

Show evidence (2 references)

PMID:23246288 SUPPORT Human Clinical

"Our observations suggest that PIK3CA and AKT1 are CS susceptibility genes."

The authors' own summary of the relationship, in the hedged form they state it.

PMID:23246288 SUPPORT Human Clinical

"We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."

Gives the PIK3CA carrier count in PTEN-negative Cowden syndrome and the pathway readout that links it to the PI3K/AKT node.

Cowden Syndrome 6 (AKT1) MONDO:0014048

AKT1 hgnc:391

PTEN-negative Cowden-like syndrome associated with activating germline AKT1 variants, reported in 2 of 91 PTEN-negative CS probands in the same study that reported the PIK3CA arm. The whole genetic evidence is two missense variants in two probands in one publication, and ClinGen's Childhood, Adolescent and Young Adult Cancer Predisposition panel grades the relationship Limited. AKT1 is the direct effector of the PI3K/AKT axis that PTEN loss also activates, so the mechanism is shared with CS1 and CS5 even where the genetic evidence is thin.

Show evidence (3 references)

CGGV:assertion_1333bd6d-332b-4c75-8811-cde8efce2001-2024-11-12T170000.000Z SUPPORT Other

"In summary, there is limited evidence supporting the relationship between AKT1 and autosomal dominant Cowden syndrome."

ClinGen's own verdict on this subtype's gene-disease relationship, and the reason the row records the evidence as thin rather than established.

CGGV:assertion_1333bd6d-332b-4c75-8811-cde8efce2001-2024-11-12T170000.000Z SUPPORT Other

"Two missense variants in AKT1 that have been reported in two probands in one publication (PMID: 23246288) are included in this curation."

Quantifies the genetic evidence base, which is the two probands reported by Orloff et al. and nothing since.

PMID:23246288 SUPPORT Human Clinical

"We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."

The primary report of the two AKT1 probands, with the phospho-AKT and PIP3 readout.

Cowden Syndrome 7 (SEC23B) MONDO:0014802

SEC23B hgnc:10702

PTEN-negative Cowden syndrome associated with germline heterozygous variants in SEC23B, which encodes a component of the COPII coat that carries cargo from the endoplasmic reticulum to the Golgi. The evidence is one multi-generation family plus 3 of 96 unrelated PTEN-negative CS probands with thyroid cancer, and the proposed mechanism is ER stress rather than PI3K/AKT activation, so this subtype does not converge on the pathway the other six share. Biallelic SEC23B variants cause an unrelated disorder, congenital dyserythropoietic anemia type II, which is the only SEC23B relationship ClinGen has curated. No independent replication of the Cowden association has been published.

Show evidence (3 references)

PMID:26522472 SUPPORT Human Clinical

"We also found germline heterozygous SEC23B variants in 3/96 (3%) unrelated mutation-negative CS probands with thyroid cancer and in The Cancer Genome Atlas (TCGA), representing apparently sporadic cancers."

The cohort evidence for this subtype beyond the index family, and the share of PTEN-negative CS probands it accounts for.

PMID:26522472 SUPPORT BACKGROUND Other

"SEC23B encodes Sec23 homolog B (S. cerevisiae), a component of coat protein complex II (COPII), which transports proteins from the endoplasmic reticulum (ER) to the Golgi apparatus."

States what the gene product does, which is why this subtype is wired to an ER-stress node rather than to the PI3K/AKT node.

PMID:26522472 SUPPORT In Vitro

"By characterizing the p.Val594Gly variant in a normal thyroid cell line, we show that it is a functional alteration that results in ER-stress-mediated cell-colony formation and survival, growth, and invasion, which reflect aspects of a cancer phenotype."

The functional evidence for the ER-stress mechanism, obtained in a thyroid cell line rather than in patients.

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Mechanistic Hypotheses

1

PTEN loss and SDHx variants converge on reduced succinate dehydrogenase activity

pten_sdhx_succinate_convergence EMERGING

Evidence balance 2 support

Cowden and Cowden-like syndrome have genetically unrelated causes: PTEN loss of function, KLLN promoter hypermethylation, and SDHB/SDHD variants. This hypothesis proposes they converge biochemically, on reduced succinate dehydrogenase catalytic activity and consequent succinate accumulation. It matters because it would explain why clinically indistinguishable patients carry unrelated genotypes, and because it would give the PTEN-negative arm a mechanism rather than a list of candidate genes. The supporting data are one study of 21 mutation carriers. The proposed direction - that PTEN loss reduces SDH activity - has not been tested directly; the study measured the metabolite and inferred the enzyme.

Not independently replicated. Recorded as EMERGING rather than ALTERNATIVE because it is not a competing account of the same data but a proposed extension covering cases the canonical PI3K/AKT/mTOR model does not reach.

Pathograph links

PTEN Loss and PI3K/AKT/mTOR Pathway Activation -> Reduced Succinate Dehydrogenase Activity UNKNOWN Proposed, not established. Plasma succinate is elevated in PTEN mutation carriers as well as in SDHx carriers, and the authors infer that PTEN loss reduces succinate dehydrogenase catalytic activity. The step from the measured metabolite to the enzyme has not been tested directly, so this edge is carried as a hypothesis rather than as a mechanism.

Show evidence (2 references)

PMID:22261759 SUPPORT Human Clinical

"Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations"

The hypothesis in the authors' own words, with their own hedge. PARTIAL because it is an inference from a metabolite measurement in a small single-centre series.

PMID:18678321 SUPPORT Human Clinical

"Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."

Establishes the two genotype groups whose convergence the hypothesis proposes, and notes their cancer spectra differ - which the convergence hypothesis must eventually explain rather than assume away.

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Discussions and Knowledge Gaps

3

Does the intensive multi-organ surveillance this entry recommends actually reduce cancer mortality in PTEN hamartoma tumour syndrome?

KNOWLEDGE GAP OPEN cs_surveillance_effectiveness

Attached to

treatments#Enhanced Cancer Surveillance

The surveillance programme is the central management recommendation of the entry and of the European guideline behind it, and it asks a great deal of patients - annual imaging across several organ systems, beginning young and continuing for life. The guideline that recommends it states that its effectiveness needs prospective evaluation. So the strongest treatment recommendation in this entry rests on the size of the underlying cancer risk plus the general case for early detection, not on evidence that this programme changes outcomes. Curators should not upgrade the treatment's evidence grading on the strength of guideline endorsement alone.

Show evidence (2 references)

PMID:42463809 SUPPORT Other

"There is a need for prospective evaluation of the effectiveness of these recommendations in the PHTS population."

The guideline stating, in its own words, that the effectiveness of the recommendations it issues has not been evaluated prospectively. This is the claim the discussion turns on.

PMID:42463809 SUPPORT Other

"The proposed cancer surveillance recommendations for PHTS require significant patient commitment as well as a coordinated multidisciplinary medical approach."

Sources the burden half of the rationale. The combination - a demanding programme whose effectiveness the issuing guideline says is unevaluated - is what makes this a knowledge gap rather than a note.

Did the everolimus trial show mTOR inhibition does not work in Cowden syndrome, or that neurocognition was the wrong endpoint to test it on?

CONTROVERSY OPEN cs_mtor_inhibition_endpoint_choice

Attached to

treatments#mTOR Inhibitor Therapy clinical_trials#NCT02991807

The one randomised trial of mTOR inhibition in this disease missed its primary neurocognitive endpoint, in 46 participants over six months. It is frequently read as a negative result for the drug class. That reading may be too broad. The trial tested neurocognition, a phenotype set during fetal and early postnatal development, and asked a six-month adult and paediatric course of drug to move it. The hamartoma burden - a lesion that is actively proliferating and therefore plausibly mTOR-dependent in real time - was not the endpoint, and the striking anecdotal responses in Lhermitte-Duclos disease are in that second category. This entry records the trial result as PARTIAL rather than REFUTE for that reason.

Show evidence (2 references)

PMID:35594551 SUPPORT Human Clinical

"Everolimus is well tolerated in PHTS; adverse events were similar to previous reports. The primary efficacy endpoint did not reveal improvement."

The negative primary endpoint that this controversy is about.

PMID:27932596 SUPPORT Human Clinical

"Rapamycin should be considered in cases of Lhermitte-Duclos disease where surgical removal may not be an option"

A single case, so it settles nothing, but it is a response on a lesion endpoint rather than a cognitive one, which is the distinction this discussion turns on.

Are the reported PTEN variant-class to organ-risk correlations real enough to stratify surveillance by?

KNOWLEDGE GAP OPEN cs_genotype_phenotype_replication

Attached to

genetic#PTEN

Correlations have been reported between PTEN variant class and organ risk, with promoter variants linked to breast cancer and nonsense variants to colorectal cancer, and catalytically inactive but stable missense mutants reported as producing the most severe phenotypes. If they hold, they would let surveillance intensity be matched to variant class instead of applied uniformly, which directly affects the burden question raised in discussions#cs_surveillance_effectiveness. They are currently associations from individual cohorts without independent replication, and this entry does not act on them. Recorded so that a future curator finds the open question rather than re-deriving it.

Show evidence (1 reference)

PMID:36634299 SUPPORT Human Clinical

"We demonstrate that PTEN PVs are associated with significantly increased risk for a range of cancers."

A large, less ascertainment-biased cohort establishing the organ risks at gene level. It does not resolve the variant-class question, which is why the gap stands.

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Pathophysiology

8

PTEN Loss and PI3K/AKT/mTOR Pathway Activation

PTEN (phosphatase and tensin homolog) is a tumor suppressor that dephosphorylates phosphatidylinositol-3,4,5-trisphosphate (PIP3) to PIP2, thereby inhibiting the PI3K/AKT/mTOR signaling axis. Germline loss-of-function mutations in PTEN lead to constitutive accumulation of PIP3 and unopposed activation of AKT and downstream mTOR complex 1 (mTORC1), resulting in excessive cell proliferation, survival, and growth that underlies hamartoma formation and elevated cancer risk across multiple organ systems.

PTEN loss and SDHx variants converge on reduced succinate dehydrogenase activity

Epithelial cell CL:0000066 Fibroblast CL:0000057

PTEN hgnc:9588 PIK3CA hgnc:8975 AKT1 hgnc:391

PI3K/AKT signaling GO:0043491 ↑ INCREASED TOR signaling GO:0031929 ↑ INCREASED Cell proliferation GO:0008283 ↑ INCREASED Negative regulation of apoptosis GO:0043066 ↑ INCREASED

Experimental models

PTEN-mutant iPSC-derived forebrain organoids ORGANOID Pharmacological AKT inhibition with perifosine reduced over-activated AKT and partially corrected the cellular disorganisation in PTEN G132D organoids. This is the entry's only demonstration that the downstream pathway state, rather than PTEN itself, is what produces the cellular phenotype - and it is in human tissue.

Downstream

Hamartoma Formation

Increased Cancer Risk

Neurodevelopmental Cortical Dysfunction

Reduced Succinate Dehydrogenase Activity Proposed, not established. Plasma succinate is elevated in PTEN mutation carriers as well as in SDHx carriers, and the authors infer that PTEN loss reduces succinate dehydrogenase catalytic activity. The step from the measured metabolite to the enzyme has not been tested directly, so this edge is carried as a hypothesis rather than as a mechanism.

Show evidence (3 references)

PMID:18781191 SUPPORT Human Clinical

"PTEN is located on chromosome 10q22-23 and negatively regulates the prosurvival PI3K/Akt/mTOR pathway through its lipid phosphatase activity. Loss of PTEN activates this pathway and leads to increased cellular growth, migration, proliferation, and survival."

Directly establishes that PTEN loss leads to PI3K/AKT/mTOR hyperactivation driving cellular overgrowth, the central molecular mechanism of Cowden syndrome.

PMID:30614812 SUPPORT Human Clinical

"The tumor suppressor phosphatase and tensin homolog (PTEN) classically counteracts the PI3K/AKT/mTOR signaling cascade. Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors, as well as neurodevelopmental disorders such as..."

Confirms PTEN's role as a counterbalance to PI3K/AKT/mTOR and links germline PTEN mutations to the full PHTS spectrum including Cowden syndrome.

PMID:23246288 SUPPORT Human Clinical

"We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."

Why PIK3CA and AKT1 are bound to this node alongside PTEN: germline variants in either raise phospho-AKT and cellular PIP3, which is the state this node records, reached without any PTEN mutation.

Hamartoma Formation

Constitutive activation of PI3K/AKT/mTOR signaling in multiple cell lineages drives the abnormal but organized proliferation of tissue elements native to the affected site, producing hamartomas. In Cowden syndrome these manifest as mucocutaneous trichilemmomas, papillomatous papules, acral keratoses, gastrointestinal hamartomatous polyps, and thyroid adenomas. The hamartomas are histologically benign but serve as a marker of systemic PTEN dysfunction and elevated cancer predisposition.

Keratinocyte CL:0000312 Thyroid follicular cell CL:0002258

PTEN hgnc:9588

Hamartomatous cell proliferation GO:0008283 ↑ INCREASED

Animal models

Epithelial-specific Pten deletion (colorectal juvenile polyposis) Mouse recapitulates Reproduces the full histopathology of Cowden colorectal juvenile polyps, including the stromal alterations and progression to invasive carcinoma.

Downstream

Increased Cancer Risk

Show evidence (1 reference)

PMID:18781191 SUPPORT Human Clinical

"The PTEN hamartoma tumor syndromes (PHTS) are a collection of rare clinical syndromes characterized by germline mutations of the tumor suppressor PTEN. These syndromes are driven by cellular overgrowth, leading to benign hamartomas in virtually any organ."

Confirms that PTEN loss drives cellular overgrowth leading to hamartomas across organ systems, which is the hallmark of Cowden syndrome pathology.

Increased Cancer Risk

The same PI3K/AKT/mTOR over-activation that drives benign hamartoma formation also confers markedly elevated lifetime risks for malignancies. The cumulative lifetime risk in PTEN mutation carriers includes breast cancer (~77-85%), follicular/papillary thyroid cancer (~35-38%), endometrial cancer (~28%), renal cell carcinoma (~34%), and colorectal cancer (~9-16%). Second-hit somatic mutations or epigenetic silencing of the remaining wild-type PTEN allele accelerate neoplastic progression.

PTEN hgnc:9588

Cell proliferation GO:0008283 ↑ INCREASED

Animal models

Mammary Pten loss with constitutive Stat5 activation Mouse partially recapitulates Reproduces PTEN-driven mammary carcinogenesis, the largest organ-specific risk in the syndrome, and identifies a pathway dependency that can be removed to prevent it.

Show evidence (4 references)

PMID:23335809 SUPPORT Human Clinical

"Cumulative cancer risks at age 70 were 85% (95% CI 70% to 95%) for any cancer, 77% (95% CI 59% to 91%) for female breast cancer, and 38% (95% CI 25% to 56%) for thyroid cancer."

Quantifies the markedly elevated cumulative cancer risks in PTEN mutation carriers, establishing the clinical significance of increased cancer risk in PHTS/Cowden syndrome.

PMID:32533092 SUPPORT Human Clinical

"The projected estimated lifetime risks of cancer in individuals with PHTS range from 85 to 89% for any cancer, 67 to 85% for female breast cancer, 6 to 38% for thyroid cancer, 2 to 28% for endometrial cancer, 2 to 34% for renal cancer, 9 to 20% for colorectal cancer and 0 to 6% for melanoma."

Provides European expert consensus estimates for organ-specific lifetime cancer risks in PHTS/Cowden syndrome, supporting the multi-organ cancer predisposition mechanism.

PMID:36634299 SUPPORT Human Clinical

"We demonstrate that PTEN PVs are associated with significantly increased risk for a range of cancers."

Large multigene panel-testing cohort (727,091 individuals) provides genotype-anchored risk estimates for major PTEN-associated cancers, complementing older clinic-ascertained CLTRs with less ascertainment-biased data.

+ 1 more reference

PTEN Genome Integrity Defect

Beyond its well-known role as a lipid phosphatase, PTEN performs nuclear functions in maintaining genome integrity, including DNA double-strand break repair and chromosomal stability. Quantitative DNA damage response (DDR) modeling of PHTS patient-derived lymphoblastoid cell lines (n=43) shows that PTEN nonsense variants have less efficient DNA repair (higher residual gamma-H2AX foci 24 h after irradiation) than missense variants, and that DDR dynamics differ between PHTS-ASD/DD and PHTS-cancer phenotypic subgroups. This second molecular axis (genome instability) likely contributes to the pleiotropy of PHTS — explaining why cancer and neurodevelopmental phenotypes can both arise from germline PTEN loss without simply scaling with PI3K/AKT/mTOR over-activation.

Lymphoblastoid cell line (B lymphocyte) CL:0000236

PTEN hgnc:9588

Double-strand break repair GO:0006302 ↓ DECREASED Maintenance of genome integrity GO:0006281 ↓ DECREASED

Downstream

Increased Cancer Risk

Neurodevelopmental Cortical Dysfunction

Show evidence (2 references)

PMID:39356721 SUPPORT In Vitro

"Maintenance of genome integrity is one of the key biological functions of PTEN, but no integrative studies have been conducted to quantify the DNA damage response (DDR) in individuals with PHTS"

Establishes PTEN's nuclear genome-integrity role as a mechanistically distinct contributor to PHTS pathology beyond cytoplasmic PI3K/AKT signaling.

PMID:39356721 SUPPORT In Vitro

"We found that PTEN nonsense variants are associated with less efficient DNA damage repair ability resulting in higher DNA damage levels at 24 hours after irradiation compared to PTEN missense variants."

Provides quantitative DDR phenotyping in PHTS patient-derived LCLs, demonstrating that PTEN variant class is associated with measurable differences in DNA repair capacity, supporting genome instability as a contributor to PHTS pleiotropy.

Neurodevelopmental Cortical Dysfunction

In addition to its cell-autonomous role in restraining cell growth, PTEN regulates neuronal differentiation, dendritic arborisation, and synaptic homeostasis. Germline PTEN loss causes early-stage neuroectoderm and forebrain organoid abnormalities (disrupted neuronal differentiation, radial glia mispositioning, and altered cortical layering) and contributes to macrocephaly and autism-spectrum neurobehavioral phenotypes through PI3K/AKT/mTOR over-activation in cortical progenitors and neurons. PTEN germline mutations account for ~0.2-1% of all autism spectrum disorder (ASD) cases, ~17% of ASD with macrocephaly, and ~20-23% of PHTS individuals are diagnosed with ASD.

Neuron CL:0000540 Radial glial cell CL:0000681 Neural progenitor cell CL:0011020

PTEN hgnc:9588

Neurogenesis GO:0022008 ⚠ ABNORMAL Neuron differentiation GO:0030182 ⚠ ABNORMAL Cortical layering GO:0021799 ⚠ ABNORMAL

Experimental models

PTEN-mutant iPSC-derived forebrain organoids ORGANOID Human germline-PTEN-genotype cells reproduce disrupted neuronal differentiation, radial glial positioning and cortical layering during early forebrain development.

Animal models

Neuronal Pten deletion (macrocephaly and social-behaviour phenotypes) Mouse recapitulates Reproduces neuronal hypertrophy, altered synaptic plasticity, and social and learning deficits following Pten loss in neurons.

Downstream

Increased Cancer Risk

Show evidence (3 references)

PMID:38030818 SUPPORT In Vitro

"PTEN germline mutations account for ~0.2-1% of all autism spectrum disorder (ASD) cases, as well as ~17% of ASD patients with macrocephaly, making it one of the top ASD-associated risk genes."

Quantifies PTEN's contribution to ASD risk and establishes germline PTEN loss as a top ASD-associated gene, motivating a dedicated neurodevelopmental pathophysiology node.

PMID:38030818 SUPPORT In Vitro

"we observed disrupted neuronal differentiation, radial glia positioning, and cortical layering in both PTEN-mutant organoids at the later stage of 72+ days of development."

Direct iPSC-derived forebrain-organoid evidence that germline PTEN mutations disrupt neuronal differentiation, radial glial positioning, and cortical layering — the cellular substrates of macrocephaly and ASD in PHTS/Cowden syndrome.

PMID:33509259 SUPPORT Human Clinical

"PTEN is a well-established risk gene for autism spectrum disorder (ASD)."

Independent confirmation in a multi-center prospective human cohort that germline PTEN mutations confer ASD risk, complementing the organoid mechanistic data.

Reduced Succinate Dehydrogenase Activity

A proposed convergent node, carried explicitly as a hypothesis. Cowden and Cowden-like syndrome have genetically unrelated causes - PTEN loss, KLLN promoter hypermethylation, and SDHB/SDHD variants - and this node is the only account on offer for why they produce clinically indistinguishable disease. SDHx variants reduce succinate dehydrogenase activity by definition; the claim that PTEN loss does so as well rests on a single study of 21 carriers that measured plasma succinate and inferred the enzyme. Nothing downstream is drawn from this node, because what the accumulated succinate would then do in Cowden syndrome has not been shown.

PTEN hgnc:9588 SDHB hgnc:10681 SDHD hgnc:10683

succinate dehydrogenase activity GO:0000104 ↓ DECREASED

Show evidence (2 references)

PMID:22261759 SUPPORT Human Clinical

"Elevated plasma succinate was observed in 13/21 (62%) individuals with germline PTEN, SDHB, or SDHD mutations as compared with 5/32 (16%) controls (P < 0.001), in 10/15 (67%) individuals with pathogenic PTEN mutations but in <20% of mutation-negative individuals meeting identical criteria"

The measurement behind the node. PARTIAL because it establishes the metabolite difference, not the enzymatic step the node is named for.

PMID:18678321 SUPPORT Human Clinical

"Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."

Establishes the SDHx arm that reaches this node by a route nobody disputes, which is what makes the PTEN route worth testing.

KLLN Promoter Hypermethylation and KILLIN Silencing

The epigenetic arm of Cowden syndrome, and the route by which CS4 reaches the same cancer risk as the sequence-variant subtypes without a coding mutation anywhere. PTEN and KILLIN are transcribed in opposite directions from one bidirectional promoter at 10q23.31; germline hypermethylation of that region leaves PTEN transcription intact while collapsing KILLIN transcription, and it also blunts TP53's activation of KILLIN. Because the lesion is a methylation state rather than an allele, these patients are negative on PTEN sequencing.

KLLN hgnc:37212

epigenetic silencing of KILLIN transcription GO:0045814 ↑ INCREASED

Downstream

Increased Cancer Risk Carriers of the epimutation have higher breast and kidney cancer prevalence than PTEN mutation carriers, but no intermediate step between loss of KILLIN and transformation has been shown in these patients, so the edge is indirect with the intermediates unknown.

Show evidence (3 references)

PMID:21177507 SUPPORT Human Clinical

"Of 123 patients with Cowden syndrome or Cowden-like syndrome, 45 (37%; 95% confidence interval [CI], 29%-45%) showed hypermethylation upstream of PTEN but no transcriptional repression."

Establishes the germline hypermethylation upstream of PTEN, and that PTEN transcription itself is not repressed by it, which is what makes KILLIN rather than PTEN the silenced gene at this node.

PMID:21177507 SUPPORT Human Clinical

"The germline methylation was found to transcriptionally down-regulate KILLIN by 250-fold"

The measured silencing of KILLIN that this node is named for.

PMID:21177507 SUPPORT In Vitro

"Demethylation treatment increased only KILLIN expression 4.88-fold"

Reversing the methylation restores KILLIN and not PTEN, which is the experiment that assigns the silencing to KILLIN.

SEC23B-Associated Endoplasmic Reticulum Stress

The one proposed Cowden mechanism that does not converge on PI3K/AKT. SEC23B is a component of the COPII coat that carries cargo out of the endoplasmic reticulum to the Golgi, and the germline heterozygous variant found in the index Cowden family behaved in a thyroid cell line as a gain of a cancer-relevant phenotype mediated by ER stress rather than by pathway activation. The node is kept separate from the PI3K/AKT node for that reason, and is carried as proposed: the functional work is a single variant in a single cell line, the clinical evidence is one family plus three of 96 probands, and no independent replication has been published.

SEC23B hgnc:10702

COPII-dependent ER-to-Golgi transport GO:0006888 endoplasmic reticulum stress response GO:0034976 ↑ INCREASED

Downstream

Increased Cancer Risk Proposed, not established. The authors state the link as a suggestion and name ER stress as the possible mediator; nothing between the trafficking component and transformation has been shown in patients.

Show evidence (2 references)

PMID:26522472 SUPPORT BACKGROUND Other

"SEC23B encodes Sec23 homolog B (S. cerevisiae), a component of coat protein complex II (COPII), which transports proteins from the endoplasmic reticulum (ER) to the Golgi apparatus."

States the transport step this node's COPII binding records.

PMID:26522472 SUPPORT In Vitro

"By characterizing the p.Val594Gly variant in a normal thyroid cell line, we show that it is a functional alteration that results in ER-stress-mediated cell-colony formation and survival, growth, and invasion, which reflect aspects of a cancer phenotype."

The measurement behind the raised ER-stress response on this node, and its limits: one variant, one thyroid cell line.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

13

Breast 1

Breast Cancer Risk Breast carcinoma HP:0003002

Show evidence (1 reference)

PMID:23335809 SUPPORT Human Clinical

"Elevated SIRs were found mainly for female breast cancer (39.1, 95% CI 24.8 to 58.6), thyroid cancer in women (43.2, 95% CI 19.7 to 82.1) and in men (199.5, 95% CI 106.39 to 342.03), melanoma in women (28.3, 95% CI 7.6 to 35.4) and in men (39.4, 95% CI 10.6 to 100.9), and endometrial cancer..."

Demonstrates markedly elevated standardized incidence ratios (SIR 39.1) for breast cancer in female PTEN mutation carriers, confirming the substantially increased breast cancer risk in Cowden syndrome.

Cardiovascular 1

Vascular Anomalies Arteriovenous malformation HP:0100026

Show evidence (2 references)

PMID:39048366 SUPPORT Human Clinical

"Vascular malformations are common in CS, particularly in the extremities."

Direct clinical statement that vascular malformations are common in Cowden syndrome, with case-level evidence of spinal dural arteriovenous fistulas associated with a truncating PTEN mutation.

PMID:40120468 SUPPORT Human Clinical

"predisposes patients to hamartomas, lipomas, vascular tumors/malformations, and potential malignancies."

Independent statement of vascular tumors/malformations as a defining PHTS phenotype.

Digestive 2

Gastrointestinal Hamartomatous Polyps Hamartomatous polyposis HP:0004390

Show evidence (1 reference)

PMID:32533092 SUPPORT Human Clinical

"Polyps are common in PHTS, and these are typically hamartomas, although other types can also occur."

Confirms hamartomatous GI polyps as a common feature of PTEN hamartoma tumor syndrome/Cowden syndrome.

Colorectal Cancer Colon cancer HP:0003003

Show evidence (1 reference)

PMID:32533092 SUPPORT Human Clinical

"9 to 20% for colorectal cancer"

European expert consensus quantifies the elevated colorectal cancer risk (9-20% lifetime) that motivates including colorectal carcinoma as a recognised PHTS/Cowden phenotype.

Endocrine 1

Thyroid Abnormalities Thyroid carcinoma HP:0002890

Show evidence (1 reference)

PMID:32533092 SUPPORT Human Clinical

"There is strong evidence of an increased risk of thyroid carcinoma in PHTS with evidence that this can arise at relatively young ages."

Confirms strong clinical evidence for increased thyroid carcinoma risk in PTEN hamartoma tumor syndrome/Cowden syndrome.

Genitourinary 2

Uterine Cancer Risk Endometrial carcinoma HP:0012114

Show evidence (1 reference)

PMID:23335809 SUPPORT Human Clinical

"Elevated SIRs were found mainly for female breast cancer (39.1, 95% CI 24.8 to 58.6), thyroid cancer in women (43.2, 95% CI 19.7 to 82.1) and in men (199.5, 95% CI 106.39 to 342.03), melanoma in women (28.3, 95% CI 7.6 to 35.4) and in men (39.4, 95% CI 10.6 to 100.9), and endometrial cancer..."

Documents a substantially elevated standardized incidence ratio (SIR 48.7) for endometrial cancer in PHTS, confirming uterine cancer as a major cancer risk in Cowden syndrome.

Renal Cell Carcinoma HP:0005584

Show evidence (2 references)

PMID:32533092 SUPPORT Human Clinical

"The projected estimated lifetime risks of cancer in individuals with PHTS range from 85 to 89% for any cancer, 67 to 85% for female breast cancer, 6 to 38% for thyroid cancer, 2 to 28% for endometrial cancer, 2 to 34% for renal cancer, 9 to 20% for colorectal cancer and 0 to 6% for melanoma."

European expert consensus places lifetime renal cancer risk at 2-34%, motivating renal cell carcinoma as a distinct PHTS/Cowden phenotype with surveillance recommendations.

PMID:21177507 SUPPORT Human Clinical

"Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals."

Identifies KLLN-methylation Cowden syndrome 4 as conferring particularly elevated renal cancer risk relative to classical PTEN-mutation cases.

Head and Neck 1

Macrocephaly HP:0000256

Show evidence (1 reference)

PMID:17526800 SUPPORT Human Clinical

"Bannayan-Riley-Ruvalcaba syndrome (BRRS), with childhood onset, macrocephaly, lipomas and developmental delay, and Cowden Syndrome (CS), an adult-onset condition recognised by mucocutaneous signs, with a risk of cancers, in particular those of the thyroid and breast."

Documents macrocephaly as a characteristic feature across the PTEN mutation phenotypic spectrum, particularly in the childhood-onset BRRS form.

Musculoskeletal 1

Lipoma HP:0012032

Show evidence (2 references)

PMID:18781191 SUPPORT Human Clinical

"Bannayan-Riley-Ruvalcaba syndrome (BRRS), characterized by the developmental delay, macrocephaly, lipomas, hemangiomas, and speckled penis in males, is associated with PTEN mutations in approximately 60% of cases."

Establishes lipomas as a defining clinical feature of the BRRS end of the PHTS spectrum; CS and BRRS are now recognised as one PHTS condition with variable expression, so lipomas are a Cowden-spectrum phenotype.

PMID:40120468 SUPPORT Human Clinical

"Phosphatase and tensin homolog hamartoma tumor syndrome (PTEN Syndrome), an autosomal dominant group of disorders caused by PTEN dysregulation, predisposes patients to hamartomas, lipomas, vascular tumors/malformations, and potential malignancies."

Independent confirmation of lipomas as a recognised feature of the PTEN syndrome spectrum, including Cowden syndrome.

Nervous System 3

Lhermitte-Duclos Disease Dysplastic gangliocytoma of the cerebellum HP:0500009

Show evidence (1 reference)

PMID:37810307 SUPPORT Human Clinical

"Lhermitte-Duclos disease (LDD) is a rare tumor, with only about 300 reported cases. It often shows comorbidity with Cowden syndrome (CS); however, it can occur by itself."

Confirms the well-established association between Lhermitte-Duclos disease and Cowden syndrome in a systematic review of 302 cases, with 32.8% of LDD showing CS comorbidity.

Autism Spectrum Disorder HP:0000717

Show evidence (2 references)

PMID:38030818 SUPPORT In Vitro

"Individuals with germline PTEN mutations receive the molecular diagnosis of PTEN Hamartoma Tumor Syndrome (PHTS), an inherited cancer predisposition syndrome, about 20-23% of whom are diagnosed with ASD."

iPSC-derived forebrain organoid study (IN_VITRO) reports the 20-23% PHTS-ASD frequency in its background, citing prior human-clinical literature; classified by the publication's primary evidence type. Human-cohort confirmation is provided separately by PMID:33509259.

PMID:33509259 SUPPORT Human Clinical

"PTEN is a well-established risk gene for autism spectrum disorder (ASD)."

Multi-center prospective patient cohort confirms PTEN as an established ASD risk gene, supporting ASD as a Cowden/PHTS clinical phenotype.

Developmental Delay and Intellectual Disability Global developmental delay HP:0001263

Show evidence (3 references)

PMID:17526800 SUPPORT Human Clinical

"Bannayan-Riley-Ruvalcaba syndrome (BRRS), with childhood onset, macrocephaly, lipomas and developmental delay"

Establishes developmental delay as a defining clinical feature of the BRRS end of the PHTS spectrum (CS and BRRS are now recognised as a single PHTS condition with variable expression).

PMID:28526761 SUPPORT Human Clinical

"developmental delay, ID and/or ASD were the most common presenting signs/symptoms (66 %)"

Quantifies the combined prevalence of developmental delay, intellectual disability, and/or ASD as the most common presenting finding in a 47-patient pediatric PHTS chart-review cohort.

PMID:33509259 SUPPORT Human Clinical

"impairments in general cognitive ability are only common in PTEN-ASD. For most neurobehavioral measures, variability within and across patient groups was very large, with some patients functioning in the average or above average range in most neurocognitive domains and other patients showing..."

Multi-center prospective PHTS cohort documents the spectrum of cognitive impairment, supporting global developmental delay / intellectual disability as a distinct clinical phenotype distinguishable from ASD diagnosis itself.

Neoplasm 1

Mucocutaneous Lesions Hamartoma HP:0010566

Show evidence (1 reference)

PMID:17526800 SUPPORT Human Clinical

"Cowden Syndrome (CS), an adult-onset condition recognised by mucocutaneous signs, with a risk of cancers, in particular those of the thyroid and breast."

Establishes mucocutaneous signs as the defining clinical feature of Cowden syndrome in PTEN mutation carriers.

🧬

Genetic Associations

7

PTEN (Causative)

Gene: PTEN hgnc:9588

Autosomal dominant

Show evidence (1 reference)

PMID:21194675 SUPPORT Human Clinical

"Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome are allelic, defined by germline PTEN mutations, and collectively referred to as PTEN hamartoma tumor syndrome."

Establishes PTEN germline mutations as the defining genetic cause of Cowden syndrome in a large prospective cohort of 3042 probands.

KLLN (Causative)

Gene: KLLN hgnc:37212

Autosomal dominant

Show evidence (1 reference)

PMID:21177507 SUPPORT Human Clinical

"Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals."

Establishes KLLN germline methylation as a distinct molecular subtype of Cowden syndrome with measurably elevated cancer risks.

PIK3CA (Susceptibility in PTEN-negative Cowden-like syndrome)

Gene: PIK3CA hgnc:8975 relationship_type: SUSCEPTIBILITY

Autosomal dominant

Show evidence (1 reference)

PMID:23246288 SUPPORT Human Clinical

"We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."

Directly identifies PIK3CA germline mutations in Cowden syndrome patients lacking PTEN mutations, confirming PIK3CA as a causative gene in Cowden syndrome 5.

SDHB (Susceptibility in PTEN-negative Cowden-like syndrome)

Gene: SDHB hgnc:10681 relationship_type: SUSCEPTIBILITY

Autosomal dominant

Show evidence (1 reference)

PMID:18678321 SUPPORT Human Clinical

"Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."

Establishes SDHB germline mutations as a contributor in Cowden syndrome 2, found in PTEN-mutation-negative individuals with elevated cancer risk.

SDHD (Susceptibility in PTEN-negative Cowden-like syndrome)

Gene: SDHD hgnc:10683 relationship_type: SUSCEPTIBILITY

Autosomal dominant

Show evidence (2 references)

PMID:18678321 SUPPORT Human Clinical

"Among these, 10 (13.5%) had germline mutations/variants in SDHB (n = 3) or SDHD (7), not found in 700 controls (p < 0.001)."

Reports the seven SDHD carriers, absent from the 700 controls screened, that are the genetic evidence for this row.

PMID:22261759 SUPPORT Human Clinical

"Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations"

Names SDHD alongside SDHB and PTEN as reaching the succinate dehydrogenase node, which is where this gene is wired in the pathograph.

AKT1 (Susceptibility in PTEN-negative Cowden-like syndrome)

Gene: AKT1 hgnc:391 relationship_type: SUSCEPTIBILITY

Autosomal dominant

Show evidence (2 references)

PMID:23246288 SUPPORT Human Clinical

"Our observations suggest that PIK3CA and AKT1 are CS susceptibility genes."

The authors' own statement of the relationship, in the hedged form they give it.

CGGV:assertion_1333bd6d-332b-4c75-8811-cde8efce2001-2024-11-12T170000.000Z SUPPORT Other

"AKT1 | HGNC:391 | Cowden syndrome 6 | MONDO:0014048 | AD | Limited | SOP11"

The ClinGen gene-disease validity row for this exact subtype concept, giving the Limited classification this record is qualified by.

SEC23B (Susceptibility in PTEN-negative Cowden syndrome)

Gene: SEC23B hgnc:10702 relationship_type: SUSCEPTIBILITY

Autosomal dominant

Show evidence (2 references)

PMID:26522472 SUPPORT In Vitro

"By characterizing the p.Val594Gly variant in a normal thyroid cell line, we show that it is a functional alteration that results in ER-stress-mediated cell-colony formation and survival, growth, and invasion, which reflect aspects of a cancer phenotype."

The functional support for the index family's variant, obtained in a thyroid cell line rather than in patient tissue.

PMID:26522472 SUPPORT BACKGROUND Other

"Interestingly, germline homozygous or compound-heterozygous SEC23B mutations cause an unrelated disorder, congenital dyserythropoietic anemia type II, and SEC23B-deficient mice suffer from secretory organ degeneration due to ER-stress-associated apoptosis."

Records that the established SEC23B disease is a different, recessive disorder, which is why the Cowden relationship is carried here as unreplicated.

💊

Medical Actions

4

Enhanced Cancer Surveillance

Action: cancer surveillance Ontology label: Cancer Screening NCIT:C15406

PTEN mutation carriers require life-long intensified surveillance protocols. GeneReviews and ERN GENTURIS support organ-specific surveillance that includes breast awareness and clinical examination, annual breast MRI beginning around age 30 with mammography incorporated by age 40, yearly thyroid ultrasound, dermatologic evaluation, baseline colonoscopy at age 35-40 with intervals based on findings, renal imaging from age 40, and earlier screening 5-10 years before the youngest cancer in a family when family history indicates. Endometrial surveillance should be framed as consideration rather than universal screening: GeneReviews recommends considering screening by age 35 with endometrial biopsy every 1-2 years and/or postmenopausal transvaginal ultrasound at clinician discretion, while ERN GENTURIS notes weak evidence and recommends symptom education or clinical-trial-based screening.

Show evidence (5 references)

PMID:32533092 SUPPORT Human Clinical

"Recommendations were put forward for surveillance for breast, thyroid and renal cancers. Limited recommendations were developed for other sites including endometrial, colon and skin."

Provides evidence-based surveillance recommendations for PHTS/Cowden syndrome from the European Reference Network for Genetic Tumour Risk Syndromes.

PMID:20301661 SUPPORT Human Clinical

"Women beginning at age 30 years. Monthly breast self-examination; annual breast screening (at minimum mammogram; MRI may also be incorporated). Starting by age 35 years, consider transvaginal ultrasound or endometrial biopsy."

GeneReviews supports breast screening from age 30 and consideration of endometrial screening from age 35.

PMID:20301661 SUPPORT Human Clinical

"Men and women. Colonoscopy beginning at age 35 years with frequency dependent on degree of polyposis identified or family history of early-onset colon cancer (before age 40); biennial (every 2 years) renal imaging (CT or MRI preferred) beginning at age 40 years."

GeneReviews supports colorectal and renal surveillance age/interval guidance.

+ 2 more references

Prophylactic Mastectomy

Action: prophylactic mastectomy Ontology label: Surgical Procedure NCIT:C15329

Platform: Surgery

Risk-reducing bilateral mastectomy reduces breast cancer risk by more than 90% in PTEN mutation carriers with high personal or family risk. It is offered as an option after careful counseling regarding elevated lifetime risk, using the same approach as for BRCA1/BRCA2 carriers.

Mechanism Target:

INHIBITS Increased Cancer Risk — Unlike surveillance, risk-reducing mastectomy removes the tissue in which the PTEN-driven breast cancer risk is realised, so it acts on the node by removing its substrate rather than by detecting its output earlier. It addresses one organ of several, which is why it does not displace the surveillance programme.

Show evidence (1 reference)

PMID:23335809 SUPPORT Human Clinical

"Cumulative cancer risks at age 70 were 85% (95% CI 70% to 95%) for any cancer, 77% (95% CI 59% to 91%) for female breast cancer, and 38% (95% CI 25% to 56%) for thyroid cancer."

The magnitude of the breast-cancer risk that makes removing the tissue a proportionate intervention.

Show evidence (1 reference)

PMID:32533092 SUPPORT Human Clinical

"Risk reduction surgery should be offered using the same considerations as for women with germline BRCA1/BRCA2 pathogenic variants"

Supports offering prophylactic mastectomy in PTEN mutation carriers following the same approach as for BRCA1/BRCA2, given comparable breast cancer risk levels.

mTOR Inhibitor Therapy

Action: mTOR inhibitor pharmacotherapy Ontology label: Pharmacotherapy NCIT:C15986

Agent: mTOR inhibitor NCIT:C2201 everolimus CHEBI:68478

Everolimus (RAD001), an mTORC1 inhibitor, targets the hyperactivated PI3K/AKT/mTOR pathway in Cowden syndrome. The mechanistic rationale stems directly from PTEN loss driving constitutive mTOR activation. A 6-month phase II placebo-controlled randomised trial of everolimus in 46 PHTS individuals (5-45 years) demonstrated that the drug is well tolerated; the primary neurocognitive endpoint was not met but several secondary neurobehavioral measures and EEG biomarkers showed signals of improvement, supporting continued investigation rather than routine clinical use.

Mechanism Target:

INHIBITS PTEN Loss and PI3K/AKT/mTOR Pathway Activation — Everolimus inhibits mTORC1 directly, acting on the de-repressed limb of the pathway rather than restoring PTEN. This is the only mechanism-directed treatment in the entry; every other entry here detects or removes disease rather than acting on the mechanism. Whether the inhibition translates into clinical benefit is unsettled - the one randomised trial missed its primary neurocognitive endpoint - so the edge records what the drug does, not that it works. See discussions#cs_mtor_inhibition_endpoint_choice.

Show evidence (1 reference)

PMID:35594551 SUPPORT Human Clinical

"PTEN hamartoma tumor syndrome (PHTS) is a complex neurodevelopmental disorder characterized by mechanistic target of rapamycin (mTOR) overactivity. Limited data suggest that mTOR inhibitors may be therapeutic."

States the target and the overactivity it acts on. PARTIAL because the same trial did not demonstrate benefit on its primary endpoint.

Show evidence (3 references)

PMID:35594551 SUPPORT Human Clinical

"PTEN hamartoma tumor syndrome (PHTS) is a complex neurodevelopmental disorder characterized by mechanistic target of rapamycin (mTOR) overactivity. Limited data suggest that mTOR inhibitors may be therapeutic."

Establishes the mechanistic rationale (mTOR overactivity) and motivates the placebo-controlled trial of everolimus in PHTS that this paper reports.

PMID:35594551 SUPPORT Human Clinical

"Everolimus is well tolerated in PHTS; adverse events were similar to previous reports. The primary efficacy endpoint did not reveal improvement."

Phase II RCT (n=46) shows everolimus is well tolerated in PHTS but did not meet its primary neurocognitive endpoint. Supports `PARTIAL`: pharmacology supports the mTOR-inhibition rationale, but no confirmed cognitive benefit yet — clinical use remains investigational.

PMID:18781191 SUPPORT Other

"Concomitant with improved understanding of the biology of PTEN and the PI3K/Akt/mTOR pathway, inhibitors of this pathway are being developed as anticancer agents. These medications could have applications for patients with PHTS, for whom no medical options currently exist."

Originally established the rationale for mTOR/PI3K inhibitor therapy in PHTS based on the underlying molecular mechanism (expert review, predates clinical trial data).

Genetic Counseling

Action: Genetic Counseling NCIT:C15240

Genetic counseling is recommended for all patients with suspected or confirmed Cowden syndrome and their at-risk family members, informing testing decisions, cancer risks, and surveillance strategies.

Show evidence (1 reference)

PMID:31433956 SUPPORT Human Clinical

"Timely diagnosis and understanding the natural history of PHTS are vital because early recognition enables gene-informed management, particularly as related to high-risk cancer surveillance and addressing the neurodevelopmental symptoms."

Highlights the importance of genetic diagnosis enabling gene-informed counseling and management in PHTS/Cowden syndrome.

🔬

Biochemical Markers

1

Plasma succinate (INCREASED)

Context: Elevated plasma succinate is the one biochemical finding reported to be shared across the genetically distinct causes of Cowden and Cowden-like syndrome. It was found in 62% of individuals carrying a germline PTEN, SDHB or SDHD mutation against 16% of controls, and in 67% of those with a pathogenic PTEN mutation against under 20% of mutation-negative individuals meeting the same clinical criteria. The authors interpret it as reduced succinate dehydrogenase catalytic activity common to both genotype groups. This is a single-centre finding on small numbers, has not been independently replicated, and is not in clinical use; it is curated because it is the only proposed unifying biomarker for the PTEN-positive and PTEN-negative arms of this entry.

Show evidence (2 references)

PMID:22261759 SUPPORT Human Clinical

"Elevated plasma succinate was observed in 13/21 (62%) individuals with germline PTEN, SDHB, or SDHD mutations as compared with 5/32 (16%) controls (P < 0.001), in 10/15 (67%) individuals with pathogenic PTEN mutations but in <20% of mutation-negative individuals meeting identical criteria"

Gives the measured difference against both healthy controls and, more informatively, against clinically identical mutation-negative individuals, which is what makes it a candidate discriminating marker.

PMID:22261759 SUPPORT Human Clinical

"Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations"

The mechanistic interpretation, graded PARTIAL because the study measures the metabolite and infers the enzyme activity rather than assaying it.

🔬

Diagnosis

3

Clinical Cowden syndrome diagnostic criteria

Clinical diagnosis should apply the Cowden syndrome pathognomonic, major, and minor criteria before or alongside molecular testing. Pathognomonic criteria include adult Lhermitte-Duclos disease and characteristic mucocutaneous lesions such as multiple facial trichilemmomas, oral mucosal papillomatosis with acral keratoses, or multiple palmoplantar keratoses. Major criteria include breast cancer, non-medullary thyroid cancer, macrocephaly, and endometrial carcinoma. Minor criteria include other thyroid lesions, intellectual disability, hamartomatous intestinal polyps, lipomas, fibromas, genitourinary tumors including renal cell carcinoma, genitourinary malformations, and uterine fibroids. A clinical diagnosis is met by a pathognomonic mucocutaneous pattern, two or more major criteria, one major plus at least three minor criteria, or four or more minor criteria.

clinical assessment NCIT:C124351

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable SUPPORT Other

"Consensus clinical diagnostic criteria have been divided into three categories: pathognomonic, major, and minor."

GeneReviews provides the pathognomonic/major/minor clinical criteria framework for Cowden syndrome.

url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable SUPPORT Other

"A clinical diagnosis of CS is established if an individual meets any one of the following criteria:"

GeneReviews supports applying rule-based clinical diagnostic combinations before or alongside molecular confirmation.

PTEN molecular genetic testing cascade

Molecular confirmation of classic PHTS/Cowden syndrome is by identifying a heterozygous germline pathogenic PTEN variant. Testing should start with PTEN sequence analysis, then deletion/duplication analysis if sequencing is negative, and PTEN promoter sequencing if no pathogenic variant is found. If the phenotype remains Cowden-like without a PTEN finding, consider Cowden-like susceptibility mechanisms such as KLLN epimutation, SDHx, PIK3CA, AKT1, SEC23B, and WWP1 rather than treating them as equivalent to classic PTEN Cowden syndrome.

molecular genetic testing NCIT:C19770

Show evidence (3 references)

PMID:20301661 SUPPORT Human Clinical

"The diagnosis of PHTS is established in a proband by identification of a heterozygous germline PTEN pathogenic variant on molecular genetic testing."

GeneReviews establishes heterozygous germline PTEN pathogenic variation as the molecular diagnostic basis for PHTS.

url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable SUPPORT Other

"Sequence analysis of PTEN is performed first and followed by gene-targeted deletion/duplication analysis if no pathogenic variant is found."

GeneReviews supports the PTEN sequence-first, deletion/duplication-second testing cascade.

url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable SUPPORT Other

"Susceptibility genes in individuals with non-PHTS CS and CLS."

GeneReviews separates non-PHTS Cowden/Cowden-like susceptibility genes from classic PTEN-defined PHTS.

Testing and counseling of at-risk relatives

Once a familial PTEN pathogenic variant is identified, asymptomatic at-risk relatives should be offered molecular testing so that carriers can enter organ-specific surveillance and non-carriers can avoid unnecessary PHTS surveillance. Counseling should cover autosomal dominant inheritance, incomplete clinical recognition, cancer risks, reproductive options, and the need for surveillance beginning before many cancers develop.

molecular genetic testing NCIT:C19770

Show evidence (1 reference)

PMID:20301661 SUPPORT Human Clinical

"When a PTEN pathogenic variant has been identified in a proband, molecular genetic testing of asymptomatic at-risk relatives can identify those who have the family-specific pathogenic variant and warrant ongoing surveillance."

GeneReviews supports familial variant testing to determine which relatives need PHTS surveillance.

📊

Prevalence

1

Global clinically recognized populations

Point Prevalence 0.5 per 100,000 1–9 per 1,000,000

Cowden syndrome is typically reported as affecting about 1 in 200,000 individuals or live births in clinically recognized populations, although this likely underestimates true PTEN-hamartoma-spectrum burden because phenotypic expression is variable.

Show evidence (2 references)

PMID:21177507 SUPPORT Human Clinical

"Germline loss-of-function phosphatase and tensin homolog gene (PTEN) mutations cause 80% of Cowden syndrome, a rare autosomal-dominant disorder (1 in 200,000 live births)"

This JAMA study explicitly states the standard prevalence estimate for Cowden syndrome.

PMID:29469739 SUPPORT Human Clinical

"Cowden syndrome affects 1:200,000 individuals."

This review-style clinical report independently gives the same population estimate.

🔬

Clinical Trials

1

NCT02991807 PHASE_II COMPLETED

A six-month randomized, double-blind, placebo-controlled phase II trial of everolimus (RAD001) in 46 individuals (5-45 years) with PTEN mutations, examining safety and efficacy on neurocognitive and behavioral outcomes in PHTS. Reported in Srivastava et al. 2022 (PMID:35594551). The primary neurocognitive endpoint was not met; everolimus was well tolerated and several secondary measures and EEG biomarkers showed signals of improvement.

Target Phenotypes: Autism HP:0000717 Global developmental delay HP:0001263

Show evidence (1 reference)

clinicaltrials:NCT02991807 SUPPORT Human Clinical

"Investigators are conducting research to evaluate the potential safety and efficacy of RAD001 (everolimus) in this patient population, and the potential neurocognitive benefits from treatment with RAD001 or placebo for a six month period."

ClinicalTrials.gov record for the everolimus phase II RCT in PHTS — formal registry capture of the study reported as PMID:35594551 in the mTOR Inhibitor Therapy treatment entry.

🧫

Experimental Models

1

PTEN-mutant iPSC-derived forebrain organoids ORGANOID

Forebrain organoids differentiated from gene-edited isogenic iPSCs carrying one of two germline PTEN missense alleles - G132D, associated with autism, and M134R, associated with cancer. The entry already cited this work as evidence on the neurodevelopmental node; it is modelled here as a system so the node carries the fidelity and limitations of the evidence, not only its conclusion. Its distinctive value is stage resolution, and the finding that resolution produced: the two alleles do not act at the same point. G132D disrupts neuroectoderm formation within the first several days, while M134R is morphologically normal then and diverges only later. Both converge on disrupted differentiation, radial glia positioning and cortical layering by 72+ days. This is human tissue, which the mouse models are not.

Publication

PMID:38030818

Pathograph links

Neurodevelopmental Cortical Dysfunction recapitulates fidelity: moderate Human germline-PTEN-genotype cells reproduce disrupted neuronal differentiation, radial glial positioning and cortical layering during early forebrain development.

Limitations: Organoids lack vasculature, microglia and the full complement of inter-areal connectivity, so behavioural and circuit-level consequences cannot be read out at all. The two alleles also diverge on different timescales, and the entry should not be read as giving one window: the ASD-associated PTEN G132D allele disrupts neuroectoderm formation within the first several days of organoid generation, whereas the M134R allele associated with cancer looks like wild type at that stage and only diverges by 72+ days. Both windows correspond to fetal development, not to the postnatal period in which macrocephaly and autism-spectrum features are recognised clinically.

Readouts

Neuronal differentiation, radial glial positioning and cortical layering

Direction: ALTERED

Interpretation: Morphological readouts scored in PTEN-mutant versus isogenic control organoids at matched differentiation stages.

Show evidence (1 reference)

PMID:38030818 SUPPORT In Vitro

"we observed disrupted neuronal differentiation, radial glia positioning, and cortical layering in both PTEN-mutant organoids at the later stage of 72+ days of development."

Names the three measured readouts and the differentiation stage at which they diverge.

PTEN Loss and PI3K/AKT/mTOR Pathway Activation rescues fidelity: moderate Pharmacological AKT inhibition with perifosine reduced over-activated AKT and partially corrected the cellular disorganisation in PTEN G132D organoids. This is the entry's only demonstration that the downstream pathway state, rather than PTEN itself, is what produces the cellular phenotype - and it is in human tissue.

Limitations: Correction was partial, not complete, and was shown for the G132D allele only. Perifosine is not a Cowden syndrome treatment and the experiment says nothing about clinical benefit; it is a mechanistic rescue, and the one randomised trial of pathway inhibition in patients missed its primary endpoint.

Readouts

AKT activation and cellular organisation after perifosine

Direction: RESTORED

Interpretation: Over-activated AKT falls and the disrupted cellular organisation is partially corrected, in the same organoid system that showed the defect.

Show evidence (1 reference)

PMID:38030818 SUPPORT In Vitro

"Perifosine, an AKT inhibitor, reduced over-activated AKT and partially corrected the abnormalities in cellular organization observed in PTENG132D organoids."

Reports both measured quantities - AKT activation and cellular organisation - and states the correction was partial.

Show evidence (1 reference)

PMID:38030818 SUPPORT In Vitro

"Single cell RNAseq analyses on early-stage organoids revealed that genes related to neural cell fate were decreased in PTENG132D mutant organoids, and AKT inhibition was capable of upregulating gene signatures related to neuronal cell fate and CNS maturation pathways."

Establishes the model as informative for the pathway-activation node, on a separate measurement from the readout below: inhibiting AKT moves the transcriptional programme, not only the cellular morphology. The two layers make different claims and now rest on different sentences.

Show evidence (1 reference)

PMID:38030818 SUPPORT In Vitro

"We generated forebrain organoid cultures from gene-edited isogenic human induced pluripotent stem cells (hiPSCs) harboring a PTENG132D (ASD) or PTENM134R (cancer) mutant allele to model how these mutations interrupt neurodevelopmental processes."

States what the model is and that it was built to model germline PTEN disruption of neurodevelopment, which is the claim a link-level evidence item should make. The isogenic design is what makes the genotype, rather than donor background, the variable under study.

🐁

Animal Models

3

Epithelial-specific Pten deletion (colorectal juvenile polyposis)

Conditional deletion of Pten restricted to the colorectal epithelium. It is the first model to reproduce the colorectal juvenile polyposis of Cowden syndrome, and it settled a mechanistic question the human material could not: juvenile polyps had been attributed to somatic PTEN loss in the stroma, and this model shows epithelial loss alone is sufficient, with the stromal changes appearing as a consequence.

Species

Mouse

Genotype

Intestinal-epithelium-specific conditional Pten deletion

Genes

PTEN hgnc:9588

Publication

PMID:24200851

Pathograph links

Hamartoma Formation recapitulates fidelity: high Reproduces the full histopathology of Cowden colorectal juvenile polyps, including the stromal alterations and progression to invasive carcinoma.

Limitations: Single-tissue conditional model: it captures the colorectal manifestation and says nothing about the multi-system distribution of hamartomas that defines the syndrome clinically. Polyps form only after a long latency, so timing does not map onto the human course.

Readouts

Colorectal juvenile polyp formation and dysplastic transformation

Direction: INCREASED

Interpretation: Histopathological readout matched feature-by-feature against human Cowden juvenile polyps.

Show evidence (1 reference)

PMID:24200851 SUPPORT Model Organism

"we find that these lesions closely recapitulate all of the characteristic histopathological features of juvenile polyps seen in patients with CS, including stromal alterations and dysplastic transformation to colorectal carcinoma"

States the histopathological correspondence with human Cowden polyps that grounds the RECAPITULATES grading.

Show evidence (1 reference)

PMID:24200851 SUPPORT Model Organism

"Our transgenic model is the first to recapitulate colorectal juvenile polyposis in patients with CS. We conclude that stromal PTEN loss is not a prerequisite for the formation of juvenile polyps, and that colorectal juvenile polyps in CS are bona fide neoplastic precursor lesions."

Establishes both that the model is informative for the human lesion and the specific mechanistic conclusion it supports.

Neuronal Pten deletion (macrocephaly and social-behaviour phenotypes)

Neuron-restricted Pten loss produces enlarged neuronal soma, dendritic hypertrophy, increased synaptic density, altered long-term potentiation and depression, and deficits in learning, memory and social behaviour. These are the cellular substrates of the macrocephaly and autism-spectrum features of Cowden syndrome, and they connect the entry's Neurodevelopmental Cortical Dysfunction node to measurable synaptic physiology rather than only to organoid morphology.

Species

Mouse

Genotype

Neuron-specific Pten deletion or mutation

Genes

PTEN hgnc:9588

Publication

PMID:39812527

Pathograph links

Neurodevelopmental Cortical Dysfunction recapitulates fidelity: moderate Reproduces neuronal hypertrophy, altered synaptic plasticity, and social and learning deficits following Pten loss in neurons.

Limitations: Most published models delete Pten in neurons rather than modelling germline heterozygosity, so gene dosage is more severe than in patients. Rodent social-behaviour assays are proxies for human autism-spectrum features rather than measurements of them, and the evidence cited here is a review synthesising several models rather than one primary study.

Readouts

Neuronal soma size, dendritic arborisation and synaptic density

Direction: INCREASED

Interpretation: Structural correlates of macrocephaly and altered connectivity in Pten-deficient neurons.

Show evidence (1 reference)

PMID:39812527 SUPPORT Model Organism

"Animal models with PTEN deletion or mutation exhibit significant structural and functional neuronal abnormalities, including enlarged soma and dendritic hypertrophy, increased synaptic density"

Lists the measured structural and electrophysiological readouts across Pten models.

Show evidence (1 reference)

PMID:39812527 SUPPORT Model Organism

"These changes lead to deficits in learning and memory tasks, as well as impairments in social behaviors. PTEN mutations are associated with neurodevelopmental disorders like intellectual disability, epilepsy, and autism spectrum disorders accompanied by macrocephaly."

Connects the model phenotypes to the human neurodevelopmental features, which is what makes the models informative for this node.

Mammary Pten loss with constitutive Stat5 activation

The breast arm, which the entry's other two models do not reach. Breast cancer is the largest single risk in Cowden syndrome, and this is the model the source describes as a genuine mouse model for it. Constitutive Stat5 activation cooperates with Pten loss to accelerate preneoplastic lesions and mammary tumours; the mechanism offered is that Stat5 drives transcription of Akt1 and of both PI3K subunits, so the two lesions converge on the same prosurvival pathway from different directions. The interventional arm is the informative part: mammary-specific Stat5 ablation prevents carcinogenesis in that background, which makes the cooperation a dependency rather than an association.

Species

Mouse

Genotype

Mammary Pten loss of function with constitutively active Stat5; conditional mammary Stat5 ablation as the intervention arm

Genes

PTEN hgnc:9588 STAT5A hgnc:11366

Publication

PMID:24469394

Pathograph links

Increased Cancer Risk partially recapitulates fidelity: moderate Reproduces PTEN-driven mammary carcinogenesis, the largest organ-specific risk in the syndrome, and identifies a pathway dependency that can be removed to prevent it.

Limitations: Tumour acceleration requires constitutive Stat5 activation alongside Pten loss, which is an engineered cooperating lesion rather than something Cowden syndrome patients carry, so the model reports on a sensitised background rather than on germline PTEN heterozygosity alone. It is a single-organ model and says nothing about the thyroid, endometrial or renal risks, and the prevention result is a genetic ablation, not a drug.

Readouts

Preneoplastic lesion and mammary tumour formation

Direction: ABOLISHED

Interpretation: Mammary-specific Stat5 ablation prevents carcinogenesis in the Pten-deficient background. ABOLISHED rather than DECREASED because the source says prevented, not reduced.

Show evidence (1 reference)

PMID:24469394 SUPPORT Model Organism

"The mammary gland-specific ablation of Stat5 is sufficient to prevent mammary carcinogenesis in a genuine mouse model for Cowden syndrome."

The interventional result, in the source's own words, including its own claim that the background is a genuine Cowden syndrome model.

The source proposes Jak2/Stat5 inhibition as a breast-cancer prevention strategy in PTEN mutation carriers. That is a hypothesis from a mouse model, not a treatment, and it is deliberately not curated in treatments:.

Show evidence (1 reference)

PMID:24469394 SUPPORT Model Organism

"we observed that the constitutive activation of Stat5 cooperates with the loss of function of the tumor suppressor PTEN by accelerating the formation of preneoplastic lesions and mammary tumors"

Establishes what the model does and that Pten loss is the operative lesion, which is what makes it informative for the cancer-risk node.

{ }

Source YAML

click to show

name: Cowden Syndrome
creation_date: "2026-03-19T00:00:00Z"
description: >-
  Cowden syndrome results from germline loss-of-function variants in the tumor suppressor PTEN, which normally dephosphorylates PIP3 to restrain PI3K/AKT/mTOR signaling.
  PTEN loss leads to constitutive PI3K/AKT/mTOR pathway activation across multiple cell lineages, driving disorganized but native-tissue overgrowth.
  This produces multisystem hamartomas, neurodevelopmental features, and markedly elevated lifetime risks of breast, thyroid, endometrial, and other cancers.
category: Mendelian
disease_term:
  preferred_term: Cowden syndrome
  term:
    id: MONDO:0016063
    label: Cowden disease
synonyms:
- Cowden disease
- Multiple hamartoma syndrome
parents:
- Autosomal dominant hereditary syndrome
- Hereditary cancer syndrome
- PTEN hamartoma tumor syndrome
prevalence:
- population: Global clinically recognized populations
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_9_PER_1000000
  rate_per_100000: 0.5
  percentage: 1 in 200,000
  notes: >-
    Cowden syndrome is typically reported as affecting about 1 in 200,000
    individuals or live births in clinically recognized populations, although
    this likely underestimates true PTEN-hamartoma-spectrum burden because
    phenotypic expression is variable.
  evidence:
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline loss-of-function phosphatase and tensin homolog gene (PTEN) mutations cause 80% of Cowden syndrome, a rare autosomal-dominant disorder (1 in 200,000 live births)"
    explanation: This JAMA study explicitly states the standard prevalence estimate for Cowden syndrome.
  - reference: PMID:29469739
    reference_title: "Cowden syndrome: clinical case and a brief review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cowden syndrome affects 1:200,000 individuals."
    explanation: This review-style clinical report independently gives the same population estimate.
has_subtypes:
- name: CS1
  display_name: Cowden Syndrome 1 (PTEN)
  subtype_term:
    preferred_term: Cowden syndrome 1
    term:
      id: MONDO:0008021
      label: Cowden syndrome 1
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  description: >
    Classic Cowden syndrome caused by germline loss-of-function mutations in PTEN on
    chromosome 10q22-23, accounting for approximately 80% of cases meeting strict
    clinical diagnostic criteria. Mutations include nonsense, frameshift, missense,
    splice-site variants, and large deletions. ClinGen grades the PTEN relationship
    Definitive against PTEN hamartoma tumor syndrome, the lumped entity that includes
    Cowden syndrome; it is the only one of the seven subtype genes graded above
    Limited.
  evidence:
  - reference: PMID:24136893
    reference_title: "Cowden syndrome and the PTEN hamartoma tumor syndrome: systematic review and revised diagnostic criteria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although it was initially reported that approximately 80% of patients with Cowden syndrome had an identifiable germline PTEN mutation, more recent work has shown these diagnostic criteria to be far less specific."
    explanation: "Establishes PTEN mutation as the predominant genetic cause in Cowden syndrome 1, noting that original ~80% frequency estimates derived from clinically ascertained cohorts."
  - reference: CGGV:assertion_2e9e89c0-8d1b-4276-bd6f-90c7b7190ffb-2024-04-05T170000.000Z
    reference_title: PTEN / PTEN hamartoma tumor syndrome (Definitive)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "PTEN | HGNC:9588 | PTEN hamartoma tumor syndrome | MONDO:0017623 | AD | Definitive | SOP10"
    explanation: >-
      ClinGen's Hereditary Cancer expert panel grades the PTEN relationship
      Definitive, against Limited for AKT1 and no assertion at all for the other
      five subtype genes.
- name: CS2
  display_name: Cowden Syndrome 2 (SDHB)
  subtype_term:
    preferred_term: Cowden syndrome 2
    term:
      id: MONDO:0012878
      label: Cowden syndrome 2
  genes:
  - preferred_term: SDHB
    term:
      id: hgnc:10681
      label: SDHB
  description: >
    PTEN-negative Cowden/Cowden-like syndrome associated with germline variants in
    succinate dehydrogenase subunit B. Three of the ten SDHx carriers in the series
    that defined this subtype carried an SDHB variant. These variants are better
    framed as Cowden-like susceptibility alleles than as classic PTEN-defined Cowden
    syndrome causes: ClinGen has curated SDHB only against hereditary
    pheochromocytoma-paraganglioma and mitochondrial disease, not against Cowden
    syndrome. The carriers were selected on raised manganese superoxide dismutase
    expression as a marker of mitochondrial dysfunction, and in the absence of PTEN
    alteration their variants raise phospho-AKT and phospho-MAPK.
  evidence:
  - reference: PMID:18678321
    reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among these, 10 (13.5%) had germline mutations/variants in SDHB (n = 3) or SDHD (7), not found in 700 controls (p < 0.001)."
    explanation: >-
      Gives the per-gene carrier counts that separate this SDHB subtype from the
      SDHD subtype, with the control comparison.
  - reference: PMID:18678321
    reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."
    explanation: "Establishes germline SDHx variants as a contributor in Cowden/Cowden-like syndrome in PTEN-mutation-negative individuals with elevated cancer risk."
- name: CS3
  display_name: Cowden Syndrome 3 (SDHD)
  subtype_term:
    preferred_term: Cowden syndrome 3
    term:
      id: MONDO:0014045
      label: Cowden syndrome 3
  genes:
  - preferred_term: SDHD
    term:
      id: hgnc:10683
      label: SDHD
  description: >
    The SDHD counterpart of CS2, and the larger of the two SDHx arms: seven of the
    ten SDHx carriers in the defining series carried an SDHD variant. The same
    caveats apply as for CS2 - the relationship is a PTEN-negative Cowden-like
    susceptibility rather than a classic Cowden syndrome cause, and ClinGen has
    curated SDHD only against hereditary pheochromocytoma-paraganglioma and
    mitochondrial disease.
  evidence:
  - reference: PMID:18678321
    reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among these, 10 (13.5%) had germline mutations/variants in SDHB (n = 3) or SDHD (7), not found in 700 controls (p < 0.001)."
    explanation: >-
      Reports the seven SDHD carriers that define this subtype, distinct from the
      three SDHB carriers recorded under CS2.
- name: CS4
  display_name: Cowden Syndrome 4 (KLLN)
  subtype_term:
    preferred_term: Cowden syndrome 4
    term:
      id: MONDO:0014046
      label: Cowden syndrome 4
  genes:
  - preferred_term: KLLN
    term:
      id: hgnc:37212
      label: KLLN
  description: >
    Cowden syndrome caused by germline epigenetic silencing (promoter hypermethylation)
    of KILLIN (KLLN), a p53-co-regulated tumor suppressor transcribed from the same
    bidirectional promoter as PTEN. KLLN methylation down-regulates KILLIN expression
    and is associated with increased breast and renal cancer risk. This is the one
    subtype whose lesion is an epimutation rather than a sequence variant, and the
    authors of the defining study asked for their observations to be replicated.
  evidence:
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals."
    explanation: "Defines KLLN germline epigenetic silencing as a cause of Cowden/Cowden-like syndrome, conferring higher breast and kidney cancer risk than PTEN mutation alone."
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The germline methylation was found to transcriptionally down-regulate KILLIN by 250-fold"
    explanation: >-
      The measured effect of the epimutation on KILLIN expression, which is the
      molecular lesion this subtype is defined by.
- name: CS5
  display_name: Cowden Syndrome 5 (PIK3CA)
  subtype_term:
    preferred_term: Cowden syndrome 5
    term:
      id: MONDO:0014047
      label: Cowden syndrome 5
  genes:
  - preferred_term: PIK3CA
    term:
      id: hgnc:8975
      label: PIK3CA
  description: >
    PTEN-negative Cowden-like syndrome associated with activating germline variants in
    PIK3CA, the catalytic subunit of PI3-kinase, reported in 8 of 91 PTEN-negative CS
    probands. These variants are better framed as Cowden-like susceptibility alleles
    than as classic PTEN-defined Cowden syndrome causes. Reported variants raise
    phospho-AKT and cellular PIP3, mimicking PTEN loss at the pathway level. ClinGen
    has no Cowden assertion for PIK3CA, and grades PIK3CA against hereditary breast
    carcinoma as Refuted.
  evidence:
  - reference: PMID:23246288
    reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our observations suggest that PIK3CA and AKT1 are CS susceptibility genes."
    explanation: "The authors' own summary of the relationship, in the hedged form they state it."
  - reference: PMID:23246288
    reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."
    explanation: "Gives the PIK3CA carrier count in PTEN-negative Cowden syndrome and the pathway readout that links it to the PI3K/AKT node."
- name: CS6
  display_name: Cowden Syndrome 6 (AKT1)
  subtype_term:
    preferred_term: Cowden syndrome 6
    term:
      id: MONDO:0014048
      label: Cowden syndrome 6
  genes:
  - preferred_term: AKT1
    term:
      id: hgnc:391
      label: AKT1
  description: >
    PTEN-negative Cowden-like syndrome associated with activating germline AKT1
    variants, reported in 2 of 91 PTEN-negative CS probands in the same study that
    reported the PIK3CA arm. The whole genetic evidence is two missense variants in
    two probands in one publication, and ClinGen's Childhood, Adolescent and Young
    Adult Cancer Predisposition panel grades the relationship Limited. AKT1 is the
    direct effector of the PI3K/AKT axis that PTEN loss also activates, so the
    mechanism is shared with CS1 and CS5 even where the genetic evidence is thin.
  evidence:
  - reference: CGGV:assertion_1333bd6d-332b-4c75-8811-cde8efce2001-2024-11-12T170000.000Z
    reference_title: AKT1 / Cowden syndrome 6 (Limited)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In summary, there is limited evidence supporting the relationship between AKT1 and autosomal dominant Cowden syndrome."
    explanation: >-
      ClinGen's own verdict on this subtype's gene-disease relationship, and the
      reason the row records the evidence as thin rather than established.
  - reference: CGGV:assertion_1333bd6d-332b-4c75-8811-cde8efce2001-2024-11-12T170000.000Z
    reference_title: AKT1 / Cowden syndrome 6 (Limited)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Two missense variants in AKT1 that have been reported in two probands in one publication (PMID: 23246288) are included in this curation."
    explanation: >-
      Quantifies the genetic evidence base, which is the two probands reported by
      Orloff et al. and nothing since.
  - reference: PMID:23246288
    reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."
    explanation: "The primary report of the two AKT1 probands, with the phospho-AKT and PIP3 readout."
- name: CS7
  display_name: Cowden Syndrome 7 (SEC23B)
  subtype_term:
    preferred_term: Cowden syndrome 7
    term:
      id: MONDO:0014802
      label: Cowden syndrome 7
  genes:
  - preferred_term: SEC23B
    term:
      id: hgnc:10702
      label: SEC23B
  description: >
    PTEN-negative Cowden syndrome associated with germline heterozygous variants in
    SEC23B, which encodes a component of the COPII coat that carries cargo from the
    endoplasmic reticulum to the Golgi. The evidence is one multi-generation family
    plus 3 of 96 unrelated PTEN-negative CS probands with thyroid cancer, and the
    proposed mechanism is ER stress rather than PI3K/AKT activation, so this subtype
    does not converge on the pathway the other six share. Biallelic SEC23B variants
    cause an unrelated disorder, congenital dyserythropoietic anemia type II, which
    is the only SEC23B relationship ClinGen has curated. No independent replication
    of the Cowden association has been published.
  evidence:
  - reference: PMID:26522472
    reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We also found germline heterozygous SEC23B variants in 3/96 (3%) unrelated mutation-negative CS probands with thyroid cancer and in The Cancer Genome Atlas (TCGA), representing apparently sporadic cancers."
    explanation: >-
      The cohort evidence for this subtype beyond the index family, and the share
      of PTEN-negative CS probands it accounts for.
  - reference: PMID:26522472
    reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "SEC23B encodes Sec23 homolog B (S. cerevisiae), a component of coat protein complex II (COPII), which transports proteins from the endoplasmic reticulum (ER) to the Golgi apparatus."
    explanation: >-
      States what the gene product does, which is why this subtype is wired to an
      ER-stress node rather than to the PI3K/AKT node.
  - reference: PMID:26522472
    reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "By characterizing the p.Val594Gly variant in a normal thyroid cell line, we show that it is a functional alteration that results in ER-stress-mediated cell-colony formation and survival, growth, and invasion, which reflect aspects of a cancer phenotype."
    explanation: >-
      The functional evidence for the ER-stress mechanism, obtained in a thyroid
      cell line rather than in patients.
pathophysiology:
- name: PTEN Loss and PI3K/AKT/mTOR Pathway Activation
  conforms_to: "germline_two_hit_tumor_predisposition#Constitutional First-Hit Tumor Suppressor Inactivation"
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  - preferred_term: PIK3CA
    term:
      id: hgnc:8975
      label: PIK3CA
  - preferred_term: AKT1
    term:
      id: hgnc:391
      label: AKT1
  description: >
    PTEN (phosphatase and tensin homolog) is a tumor suppressor that dephosphorylates
    phosphatidylinositol-3,4,5-trisphosphate (PIP3) to PIP2, thereby inhibiting the
    PI3K/AKT/mTOR signaling axis. Germline loss-of-function mutations in PTEN lead to
    constitutive accumulation of PIP3 and unopposed activation of AKT and downstream
    mTOR complex 1 (mTORC1), resulting in excessive cell proliferation, survival, and
    growth that underlies hamartoma formation and elevated cancer risk across multiple
    organ systems.
  cell_types:
  - preferred_term: Epithelial cell
    term:
      id: CL:0000066
      label: epithelial cell
  - preferred_term: Fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: PI3K/AKT signaling
    term:
      id: GO:0043491
      label: phosphatidylinositol 3-kinase/protein kinase B signal transduction
    modifier: INCREASED
  - preferred_term: TOR signaling
    term:
      id: GO:0031929
      label: TOR signaling
    modifier: INCREASED
  - preferred_term: Cell proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: INCREASED
  - preferred_term: Negative regulation of apoptosis
    term:
      id: GO:0043066
      label: negative regulation of apoptotic process
    modifier: INCREASED
  evidence:
  - reference: PMID:18781191
    reference_title: PTEN hamartoma tumor syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PTEN is located on chromosome 10q22-23 and negatively regulates the prosurvival PI3K/Akt/mTOR pathway through its lipid phosphatase activity. Loss of PTEN activates this pathway and leads to increased cellular growth, migration, proliferation, and survival."
    explanation: "Directly establishes that PTEN loss leads to PI3K/AKT/mTOR hyperactivation driving cellular overgrowth, the central molecular mechanism of Cowden syndrome."
  - reference: PMID:30614812
    reference_title: "PTEN-opathies: from biological insights to evidence-based precision medicine."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The tumor suppressor phosphatase and tensin homolog (PTEN) classically counteracts the PI3K/AKT/mTOR signaling cascade. Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors, as well as neurodevelopmental disorders such as autism spectrum disorder."
    explanation: "Confirms PTEN's role as a counterbalance to PI3K/AKT/mTOR and links germline PTEN mutations to the full PHTS spectrum including Cowden syndrome."
  - reference: PMID:23246288
    reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."
    explanation: >-
      Why PIK3CA and AKT1 are bound to this node alongside PTEN: germline variants
      in either raise phospho-AKT and cellular PIP3, which is the state this node
      records, reached without any PTEN mutation.
  downstream:
  - target: Hamartoma Formation
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:18781191
      reference_title: PTEN hamartoma tumor syndromes.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "These syndromes are driven by cellular overgrowth, leading to benign hamartomas in virtually any organ."
      explanation: "Direct causal link from PTEN-driven PI3K/AKT/mTOR pathway hyperactivation to multi-organ hamartoma formation."
  - target: Increased Cancer Risk
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30614812
      reference_title: "PTEN-opathies: from biological insights to evidence-based precision medicine."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The tumor suppressor phosphatase and tensin homolog (PTEN) classically counteracts the PI3K/AKT/mTOR signaling cascade. Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors"
      explanation: "Indirect causal link: PTEN-driven PI3K/AKT/mTOR hyperactivation predisposes to multiple malignant tumors through downstream proliferation and survival programs."
  - target: Neurodevelopmental Cortical Dysfunction
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30614812
      reference_title: "PTEN-opathies: from biological insights to evidence-based precision medicine."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors, as well as neurodevelopmental disorders such as autism spectrum disorder."
      explanation: "Direct causal link from germline PTEN loss / pathway over-activation to cortical neurodevelopmental phenotypes including autism spectrum disorder."
  - target: Reduced Succinate Dehydrogenase Activity
    description: >-
      Proposed, not established. Plasma succinate is elevated in PTEN mutation
      carriers as well as in SDHx carriers, and the authors infer that PTEN
      loss reduces succinate dehydrogenase catalytic activity. The step from
      the measured metabolite to the enzyme has not been tested directly, so
      this edge is carried as a hypothesis rather than as a mechanism.
    causal_link_type: UNKNOWN
    hypothesis_groups:
    - pten_sdhx_succinate_convergence
    evidence:
    - reference: PMID:22261759
      reference_title: "Elevated plasma succinate in PTEN, SDHB, and SDHD mutation-positive individuals."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations"
      explanation: >-
        The proposed edge in the authors' own words, with their own hedge.
        PARTIAL because succinate was measured and the enzyme activity inferred.
- name: Hamartoma Formation
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  description: >
    Constitutive activation of PI3K/AKT/mTOR signaling in multiple cell lineages drives
    the abnormal but organized proliferation of tissue elements native to the affected
    site, producing hamartomas. In Cowden syndrome these manifest as mucocutaneous
    trichilemmomas, papillomatous papules, acral keratoses, gastrointestinal hamartomatous
    polyps, and thyroid adenomas. The hamartomas are histologically benign but serve as
    a marker of systemic PTEN dysfunction and elevated cancer predisposition.
  cell_types:
  - preferred_term: Keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  - preferred_term: Thyroid follicular cell
    term:
      id: CL:0002258
      label: thyroid follicular cell
  biological_processes:
  - preferred_term: Hamartomatous cell proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: INCREASED
  evidence:
  - reference: PMID:18781191
    reference_title: PTEN hamartoma tumor syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The PTEN hamartoma tumor syndromes (PHTS) are a collection of rare clinical syndromes characterized by germline mutations of the tumor suppressor PTEN. These syndromes are driven by cellular overgrowth, leading to benign hamartomas in virtually any organ."
    explanation: "Confirms that PTEN loss drives cellular overgrowth leading to hamartomas across organ systems, which is the hallmark of Cowden syndrome pathology."
  downstream:
  - target: Increased Cancer Risk
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30614812
      reference_title: "PTEN-opathies: from biological insights to evidence-based precision medicine."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The tumor suppressor phosphatase and tensin homolog (PTEN) classically counteracts the PI3K/AKT/mTOR signaling cascade. Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors"
      explanation: "Hamartomas serve as a clinical marker of the underlying PTEN dysfunction; the same PI3K/AKT/mTOR-hyperactivating molecular state that produces the benign hamartomas also predisposes to the malignant tumors of PHTS, hence an indirect causal contribution rather than a strict progression from individual hamartomas to malignancy."
- name: Increased Cancer Risk
  conforms_to: "germline_two_hit_tumor_predisposition#Early-Onset, Multifocal, and Bilateral Tumor Spectrum"
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  description: >
    The same PI3K/AKT/mTOR over-activation that drives benign hamartoma formation also
    confers markedly elevated lifetime risks for malignancies. The cumulative lifetime
    risk in PTEN mutation carriers includes breast cancer (~77-85%), follicular/papillary
    thyroid cancer (~35-38%), endometrial cancer (~28%), renal cell carcinoma (~34%),
    and colorectal cancer (~9-16%). Second-hit somatic mutations or epigenetic silencing
    of the remaining wild-type PTEN allele accelerate neoplastic progression.
  biological_processes:
  - preferred_term: Cell proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: INCREASED
  evidence:
  - reference: PMID:23335809
    reference_title: High cumulative risks of cancer in patients with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cumulative cancer risks at age 70 were 85% (95% CI 70% to 95%) for any cancer, 77% (95% CI 59% to 91%) for female breast cancer, and 38% (95% CI 25% to 56%) for thyroid cancer."
    explanation: "Quantifies the markedly elevated cumulative cancer risks in PTEN mutation carriers, establishing the clinical significance of increased cancer risk in PHTS/Cowden syndrome."
  - reference: PMID:32533092
    reference_title: Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The projected estimated lifetime risks of cancer in individuals with PHTS range from 85 to 89% for any cancer, 67 to 85% for female breast cancer, 6 to 38% for thyroid cancer, 2 to 28% for endometrial cancer, 2 to 34% for renal cancer, 9 to 20% for colorectal cancer and 0 to 6% for melanoma."
    explanation: "Provides European expert consensus estimates for organ-specific lifetime cancer risks in PHTS/Cowden syndrome, supporting the multi-organ cancer predisposition mechanism."
  - reference: PMID:36634299
    reference_title: Cancer Risk Associated With PTEN Pathogenic Variants Identified Using Multigene Hereditary Cancer Panel Testing.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We demonstrate that PTEN PVs are associated with significantly increased risk for a range of cancers."
    explanation: "Large multigene panel-testing cohort (727,091 individuals) provides genotype-anchored risk estimates for major PTEN-associated cancers, complementing older clinic-ascertained CLTRs with less ascertainment-biased data."
  - reference: PMID:33140411
    reference_title: A review on age-related cancer risks in PTEN hamartoma tumor syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Reported CLTRs for any cancer varied from 81% to 90%."
    explanation: "Independent meta-review of nine PHTS cohorts confirms the multi-organ lifetime cancer risk profile and the median diagnosis age of ~36 years used to motivate early surveillance."
- name: PTEN Genome Integrity Defect
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  description: >
    Beyond its well-known role as a lipid phosphatase, PTEN performs nuclear functions
    in maintaining genome integrity, including DNA double-strand break repair and
    chromosomal stability. Quantitative DNA damage response (DDR) modeling of PHTS
    patient-derived lymphoblastoid cell lines (n=43) shows that PTEN nonsense variants
    have less efficient DNA repair (higher residual gamma-H2AX foci 24 h after
    irradiation) than missense variants, and that DDR dynamics differ between
    PHTS-ASD/DD and PHTS-cancer phenotypic subgroups. This second molecular axis (genome
    instability) likely contributes to the pleiotropy of PHTS — explaining why cancer
    and neurodevelopmental phenotypes can both arise from germline PTEN loss without
    simply scaling with PI3K/AKT/mTOR over-activation.
  cell_types:
  - preferred_term: Lymphoblastoid cell line (B lymphocyte)
    term:
      id: CL:0000236
      label: B cell
  biological_processes:
  - preferred_term: Double-strand break repair
    term:
      id: GO:0006302
      label: double-strand break repair
    modifier: DECREASED
  - preferred_term: Maintenance of genome integrity
    term:
      id: GO:0006281
      label: DNA repair
    modifier: DECREASED
  evidence:
  - reference: PMID:39356721
    reference_title: Quantitative evaluation of DNA damage repair dynamics to elucidate predictors of autism vs. cancer in individuals with germline PTEN variants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Maintenance of genome integrity is one of the key biological functions of PTEN, but no integrative studies have been conducted to quantify the DNA damage response (DDR) in individuals with PHTS"
    explanation: "Establishes PTEN's nuclear genome-integrity role as a mechanistically distinct contributor to PHTS pathology beyond cytoplasmic PI3K/AKT signaling."
  - reference: PMID:39356721
    reference_title: Quantitative evaluation of DNA damage repair dynamics to elucidate predictors of autism vs. cancer in individuals with germline PTEN variants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We found that PTEN nonsense variants are associated with less efficient DNA damage repair ability resulting in higher DNA damage levels at 24 hours after irradiation compared to PTEN missense variants."
    explanation: "Provides quantitative DDR phenotyping in PHTS patient-derived LCLs, demonstrating that PTEN variant class is associated with measurable differences in DNA repair capacity, supporting genome instability as a contributor to PHTS pleiotropy."
  downstream:
  - target: Increased Cancer Risk
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:39356721
      reference_title: Quantitative evaluation of DNA damage repair dynamics to elucidate predictors of autism vs. cancer in individuals with germline PTEN variants.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "PHTS confers high risks of specific malignancies, and up to 23% of the patients are diagnosed with autism spectrum disorder (ASD) and/or developmental delay (DD)."
      explanation: "Genome-integrity loss is mechanistically expected to contribute directly to malignant transformation; the DDR phenotyping data support this axis as part of the cancer-predisposition explanation alongside PI3K/AKT/mTOR over-activation."
  - target: Neurodevelopmental Cortical Dysfunction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:39356721
      reference_title: Quantitative evaluation of DNA damage repair dynamics to elucidate predictors of autism vs. cancer in individuals with germline PTEN variants.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "LCLs from PHTS individuals with ASD/DD showed faster DNA damage repairing rate than those from patients without ASD/DD or cancer."
      explanation: "DDR dynamics differ between PHTS-ASD/DD and PHTS-cancer phenotypic subgroups, suggesting genome-integrity differences contribute through unknown intermediates to neurodevelopmental versus oncologic phenotypic divergence."
- name: Neurodevelopmental Cortical Dysfunction
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  description: >
    In addition to its cell-autonomous role in restraining cell growth, PTEN regulates
    neuronal differentiation, dendritic arborisation, and synaptic homeostasis. Germline
    PTEN loss causes early-stage neuroectoderm and forebrain organoid abnormalities
    (disrupted neuronal differentiation, radial glia mispositioning, and altered cortical
    layering) and contributes to macrocephaly and autism-spectrum neurobehavioral
    phenotypes through PI3K/AKT/mTOR over-activation in cortical progenitors and neurons.
    PTEN germline mutations account for ~0.2-1% of all autism spectrum disorder (ASD)
    cases, ~17% of ASD with macrocephaly, and ~20-23% of PHTS individuals are diagnosed
    with ASD.
  cell_types:
  - preferred_term: Neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: Radial glial cell
    term:
      id: CL:0000681
      label: radial glial cell
  - preferred_term: Neural progenitor cell
    term:
      id: CL:0011020
      label: neural progenitor cell
  biological_processes:
  - preferred_term: Neurogenesis
    term:
      id: GO:0022008
      label: neurogenesis
    modifier: ABNORMAL
  - preferred_term: Neuron differentiation
    term:
      id: GO:0030182
      label: neuron differentiation
    modifier: ABNORMAL
  - preferred_term: Cortical layering
    term:
      id: GO:0021799
      label: cerebral cortex radially oriented cell migration
    modifier: ABNORMAL
  evidence:
  - reference: PMID:38030818
    reference_title: Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "PTEN germline mutations account for ~0.2-1% of all autism spectrum disorder (ASD) cases, as well as ~17% of ASD patients with macrocephaly, making it one of the top ASD-associated risk genes."
    explanation: "Quantifies PTEN's contribution to ASD risk and establishes germline PTEN loss as a top ASD-associated gene, motivating a dedicated neurodevelopmental pathophysiology node."
  - reference: PMID:38030818
    reference_title: Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we observed disrupted neuronal differentiation, radial glia positioning, and cortical layering in both PTEN-mutant organoids at the later stage of 72+ days of development."
    explanation: "Direct iPSC-derived forebrain-organoid evidence that germline PTEN mutations disrupt neuronal differentiation, radial glial positioning, and cortical layering — the cellular substrates of macrocephaly and ASD in PHTS/Cowden syndrome."
  - reference: PMID:33509259
    reference_title: Cross-level analysis of molecular and neurobehavioral function in a prospective series of patients with germline heterozygous PTEN mutations with and without autism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PTEN is a well-established risk gene for autism spectrum disorder (ASD)."
    explanation: "Independent confirmation in a multi-center prospective human cohort that germline PTEN mutations confer ASD risk, complementing the organoid mechanistic data."
  downstream:
  - target: Increased Cancer Risk
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38030818
      reference_title: Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Individuals with germline PTEN mutations receive the molecular diagnosis of PTEN Hamartoma Tumor Syndrome (PHTS), an inherited cancer predisposition syndrome, about 20-23% of whom are diagnosed with ASD."
      explanation: "Same upstream PTEN/PI3K/AKT pathway underlies both ASD-relevant cortical phenotypes and PHTS cancer predisposition; the cancer risk arises through cell-type-specific (non-CNS) intermediates rather than a direct CNS→cancer cascade."

- name: Reduced Succinate Dehydrogenase Activity
  description: >-
    A proposed convergent node, carried explicitly as a hypothesis. Cowden and
    Cowden-like syndrome have genetically unrelated causes - PTEN loss, KLLN
    promoter hypermethylation, and SDHB/SDHD variants - and this node is the
    only account on offer for why they produce clinically indistinguishable
    disease. SDHx variants reduce succinate dehydrogenase activity by
    definition; the claim that PTEN loss does so as well rests on a single
    study of 21 carriers that measured plasma succinate and inferred the
    enzyme. Nothing downstream is drawn from this node, because what the
    accumulated succinate would then do in Cowden syndrome has not been shown.
  biological_scale: MOLECULAR
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  - preferred_term: SDHB
    term:
      id: hgnc:10681
      label: SDHB
  - preferred_term: SDHD
    term:
      id: hgnc:10683
      label: SDHD
  molecular_functions:
  - preferred_term: succinate dehydrogenase activity
    term:
      id: GO:0000104
      label: succinate dehydrogenase activity
    modifier: DECREASED
  chemical_entities:
  - preferred_term: succinate
    term:
      id: CHEBI:30031
      label: succinate(2-)
    modifier: INCREASED
  evidence:
  - reference: PMID:22261759
    reference_title: "Elevated plasma succinate in PTEN, SDHB, and SDHD mutation-positive individuals."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Elevated plasma succinate was observed in 13/21 (62%) individuals with germline PTEN, SDHB, or SDHD mutations as compared with 5/32 (16%) controls (P < 0.001), in 10/15 (67%) individuals with pathogenic PTEN mutations but in <20% of mutation-negative individuals meeting identical criteria"
    explanation: >-
      The measurement behind the node. PARTIAL because it establishes the
      metabolite difference, not the enzymatic step the node is named for.
  - reference: PMID:18678321
    reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."
    explanation: >-
      Establishes the SDHx arm that reaches this node by a route nobody
      disputes, which is what makes the PTEN route worth testing.
- name: KLLN Promoter Hypermethylation and KILLIN Silencing
  description: >-
    The epigenetic arm of Cowden syndrome, and the route by which CS4 reaches the
    same cancer risk as the sequence-variant subtypes without a coding mutation
    anywhere. PTEN and KILLIN are transcribed in opposite directions from one
    bidirectional promoter at 10q23.31; germline hypermethylation of that region
    leaves PTEN transcription intact while collapsing KILLIN transcription, and it
    also blunts TP53's activation of KILLIN. Because the lesion is a methylation
    state rather than an allele, these patients are negative on PTEN sequencing.
  biological_scale: MOLECULAR
  genes:
  - preferred_term: KLLN
    term:
      id: hgnc:37212
      label: KLLN
  biological_processes:
  - preferred_term: epigenetic silencing of KILLIN transcription
    term:
      id: GO:0045814
      label: negative regulation of gene expression, epigenetic
    modifier: INCREASED
  evidence:
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of 123 patients with Cowden syndrome or Cowden-like syndrome, 45 (37%; 95% confidence interval [CI], 29%-45%) showed hypermethylation upstream of PTEN but no transcriptional repression."
    explanation: >-
      Establishes the germline hypermethylation upstream of PTEN, and that PTEN
      transcription itself is not repressed by it, which is what makes KILLIN rather
      than PTEN the silenced gene at this node.
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The germline methylation was found to transcriptionally down-regulate KILLIN by 250-fold"
    explanation: The measured silencing of KILLIN that this node is named for.
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Demethylation treatment increased only KILLIN expression 4.88-fold"
    explanation: >-
      Reversing the methylation restores KILLIN and not PTEN, which is the
      experiment that assigns the silencing to KILLIN.
  downstream:
  - target: Increased Cancer Risk
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Carriers of the epimutation have higher breast and kidney cancer prevalence
      than PTEN mutation carriers, but no intermediate step between loss of KILLIN
      and transformation has been shown in these patients, so the edge is indirect
      with the intermediates unknown.
    evidence:
    - reference: PMID:21177507
      reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Individuals with KILLIN -promoter methylation had a 3-fold increased prevalence of breast cancer (35/42 vs 24/64; P < .0001) and a greater than 2-fold increase of kidney cancer (4/45 vs 6/155; P = .004) over individuals with germline PTEN mutations."
      explanation: >-
        Quantifies the cancer excess in epimutation carriers over PTEN mutation
        carriers, which is the risk this edge carries.
- name: SEC23B-Associated Endoplasmic Reticulum Stress
  description: >-
    The one proposed Cowden mechanism that does not converge on PI3K/AKT. SEC23B is a
    component of the COPII coat that carries cargo out of the endoplasmic reticulum to
    the Golgi, and the germline heterozygous variant found in the index Cowden family
    behaved in a thyroid cell line as a gain of a cancer-relevant phenotype mediated
    by ER stress rather than by pathway activation. The node is kept separate from the
    PI3K/AKT node for that reason, and is carried as proposed: the functional work is
    a single variant in a single cell line, the clinical evidence is one family plus
    three of 96 probands, and no independent replication has been published.
  biological_scale: MOLECULAR
  genes:
  - preferred_term: SEC23B
    term:
      id: hgnc:10702
      label: SEC23B
  biological_processes:
  - preferred_term: COPII-dependent ER-to-Golgi transport
    term:
      id: GO:0006888
      label: endoplasmic reticulum to Golgi vesicle-mediated transport
  - preferred_term: endoplasmic reticulum stress response
    term:
      id: GO:0034976
      label: response to endoplasmic reticulum stress
    modifier: INCREASED
  evidence:
  - reference: PMID:26522472
    reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "SEC23B encodes Sec23 homolog B (S. cerevisiae), a component of coat protein complex II (COPII), which transports proteins from the endoplasmic reticulum (ER) to the Golgi apparatus."
    explanation: States the transport step this node's COPII binding records.
  - reference: PMID:26522472
    reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "By characterizing the p.Val594Gly variant in a normal thyroid cell line, we show that it is a functional alteration that results in ER-stress-mediated cell-colony formation and survival, growth, and invasion, which reflect aspects of a cancer phenotype."
    explanation: >-
      The measurement behind the raised ER-stress response on this node, and its
      limits: one variant, one thyroid cell line.
  downstream:
  - target: Increased Cancer Risk
    causal_link_type: UNKNOWN
    description: >-
      Proposed, not established. The authors state the link as a suggestion and name
      ER stress as the possible mediator; nothing between the trafficking component
      and transformation has been shown in patients.
    evidence:
    - reference: PMID:26522472
      reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Our findings suggest a different role for SEC23B, whereby germline heterozygous variants associate with cancer predisposition potentially mediated by ER stress"
      explanation: >-
        The proposed edge in the authors' own words, including their own hedge on the
        mediating mechanism.

phenotypes:
- category: Clinical
  name: Mucocutaneous Lesions
  description: >
    Pathognomonic mucocutaneous findings include multiple facial trichilemmomas
    (benign hamartomas of the hair follicle outer root sheath), acral and plantar
    keratoses, and papillomatous papules of the oral mucosa (cobblestone appearance).
    These lesions are present in more than 90% of adult Cowden syndrome patients and
    are the most distinctive clinical features of the syndrome.
  phenotype_term:
    preferred_term: Skin hamartoma
    term:
      id: HP:0010566
      label: Hamartoma
  evidence:
  - reference: PMID:17526800
    reference_title: "Cowden syndrome and Bannayan Riley Ruvalcaba syndrome represent one condition with variable expression and age-related penetrance: results of a clinical study of PTEN mutation carriers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cowden Syndrome (CS), an adult-onset condition recognised by mucocutaneous signs, with a risk of cancers, in particular those of the thyroid and breast."
    explanation: "Establishes mucocutaneous signs as the defining clinical feature of Cowden syndrome in PTEN mutation carriers."
- category: Clinical
  name: Macrocephaly
  description: >
    Megalencephaly or macrocephaly (occipitofrontal circumference ≥ 97th percentile)
    is among the most prevalent features of PTEN-associated disorders, occurring in
    approximately 80% of affected individuals. It reflects PTEN's role in regulating
    neuronal cell size and cortical structure and is a prominent feature of
    Bannayan-Riley-Ruvalcaba syndrome, the childhood-onset form of PHTS.
  phenotype_term:
    preferred_term: Macrocephaly
    term:
      id: HP:0000256
      label: Macrocephaly
  evidence:
  - reference: PMID:17526800
    reference_title: "Cowden syndrome and Bannayan Riley Ruvalcaba syndrome represent one condition with variable expression and age-related penetrance: results of a clinical study of PTEN mutation carriers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bannayan-Riley-Ruvalcaba syndrome (BRRS), with childhood onset, macrocephaly, lipomas and developmental delay, and Cowden Syndrome (CS), an adult-onset condition recognised by mucocutaneous signs, with a risk of cancers, in particular those of the thyroid and breast."
    explanation: "Documents macrocephaly as a characteristic feature across the PTEN mutation phenotypic spectrum, particularly in the childhood-onset BRRS form."
- category: Clinical
  name: Breast Cancer Risk
  description: >
    PTEN mutation carriers face a lifetime breast cancer risk of approximately 77-85%,
    with both invasive carcinoma and benign fibrocystic changes being common. Risk
    management includes enhanced surveillance with annual MRI from age 30 and
    mammography from age 40, or prophylactic mastectomy.
  phenotype_term:
    preferred_term: Breast carcinoma
    term:
      id: HP:0003002
      label: Breast carcinoma
  evidence:
  - reference: PMID:23335809
    reference_title: High cumulative risks of cancer in patients with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Elevated SIRs were found mainly for female breast cancer (39.1, 95% CI 24.8 to 58.6), thyroid cancer in women (43.2, 95% CI 19.7 to 82.1) and in men (199.5, 95% CI 106.39 to 342.03), melanoma in women (28.3, 95% CI 7.6 to 35.4) and in men (39.4, 95% CI 10.6 to 100.9), and endometrial cancer (48.7, 95% CI 9.8 to 142.3)."
    explanation: "Demonstrates markedly elevated standardized incidence ratios (SIR 39.1) for breast cancer in female PTEN mutation carriers, confirming the substantially increased breast cancer risk in Cowden syndrome."
- category: Clinical
  name: Thyroid Abnormalities
  description: >
    Non-medullary thyroid cancer (follicular and papillary subtypes) occurs in
    approximately 35% of PTEN mutation carriers. Benign thyroid conditions including
    multinodular goiter, follicular adenoma, and Hashimoto thyroiditis are also
    common; up to 75% of individuals develop some thyroid disease.
  phenotype_term:
    preferred_term: Thyroid carcinoma
    term:
      id: HP:0002890
      label: Thyroid carcinoma
  evidence:
  - reference: PMID:32533092
    reference_title: Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There is strong evidence of an increased risk of thyroid carcinoma in PHTS with evidence that this can arise at relatively young ages."
    explanation: "Confirms strong clinical evidence for increased thyroid carcinoma risk in PTEN hamartoma tumor syndrome/Cowden syndrome."
- category: Clinical
  name: Uterine Cancer Risk
  description: >
    Germline PTEN mutations confer a lifetime risk of endometrial cancer of approximately
    28%, substantially higher than the general population risk (~3%). The endometrium
    is particularly sensitive to PTEN loss because somatic PTEN mutations are the most
    common alteration in sporadic endometrial cancers.
  phenotype_term:
    preferred_term: Endometrial carcinoma
    term:
      id: HP:0012114
      label: Endometrial carcinoma
  evidence:
  - reference: PMID:23335809
    reference_title: High cumulative risks of cancer in patients with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Elevated SIRs were found mainly for female breast cancer (39.1, 95% CI 24.8 to 58.6), thyroid cancer in women (43.2, 95% CI 19.7 to 82.1) and in men (199.5, 95% CI 106.39 to 342.03), melanoma in women (28.3, 95% CI 7.6 to 35.4) and in men (39.4, 95% CI 10.6 to 100.9), and endometrial cancer (48.7, 95% CI 9.8 to 142.3)."
    explanation: "Documents a substantially elevated standardized incidence ratio (SIR 48.7) for endometrial cancer in PHTS, confirming uterine cancer as a major cancer risk in Cowden syndrome."
- category: Clinical
  name: Lhermitte-Duclos Disease
  description: >
    Lhermitte-Duclos disease (LDD, dysplastic gangliocytoma of the cerebellum) is a
    pathognomonic central nervous system manifestation of Cowden syndrome, characterized
    by replacement of normal Purkinje cells with dysplastic ganglion cells. A systematic
    review of 302 LDD cases found that 32.8% were associated with Cowden syndrome and
    19.9% had confirmed PTEN mutation. Symptoms include headache (57.6%) and cerebellar
    ataxia (36.1%); the radiologic "tiger-stripe" appearance on MRI is pathognomonic.
  phenotype_term:
    preferred_term: Lhermitte-Duclos disease
    term:
      id: HP:0500009
      label: Dysplastic gangliocytoma of the cerebellum
  evidence:
  - reference: PMID:37810307
    reference_title: "Lhermitte-Duclos disease: A systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Lhermitte-Duclos disease (LDD) is a rare tumor, with only about 300 reported cases. It often shows comorbidity with Cowden syndrome (CS); however, it can occur by itself."
    explanation: "Confirms the well-established association between Lhermitte-Duclos disease and Cowden syndrome in a systematic review of 302 cases, with 32.8% of LDD showing CS comorbidity."
- category: Clinical
  name: Gastrointestinal Hamartomatous Polyps
  description: >
    Hamartomatous polyps of the gastrointestinal tract occur throughout the GI tract
    in more than 90% of individuals with Cowden syndrome. They are typically benign
    but may cause bleeding or obstruction, and are associated with a modestly increased
    colorectal cancer risk (~9-16% lifetime).
  phenotype_term:
    preferred_term: Hamartomatous intestinal polyposis
    term:
      id: HP:0004390
      label: Hamartomatous polyposis
  evidence:
  - reference: PMID:32533092
    reference_title: Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Polyps are common in PHTS, and these are typically hamartomas, although other types can also occur."
    explanation: "Confirms hamartomatous GI polyps as a common feature of PTEN hamartoma tumor syndrome/Cowden syndrome."
- category: Clinical
  name: Autism Spectrum Disorder
  description: >
    Autism spectrum disorder (ASD) is a recognised neurodevelopmental manifestation of
    PHTS/Cowden syndrome. Approximately 20-23% of PHTS individuals are diagnosed with ASD,
    and germline PTEN mutations account for ~0.2-1% of all ASD and ~17% of ASD with
    macrocephaly. ASD-associated PTEN mutations disrupt early neuroectoderm formation
    and downstream cortical layering through PI3K/AKT/mTOR over-activation in cortical
    progenitors.
  phenotype_term:
    preferred_term: Autism
    term:
      id: HP:0000717
      label: Autism
  evidence:
  - reference: PMID:38030818
    reference_title: Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Individuals with germline PTEN mutations receive the molecular diagnosis of PTEN Hamartoma Tumor Syndrome (PHTS), an inherited cancer predisposition syndrome, about 20-23% of whom are diagnosed with ASD."
    explanation: "iPSC-derived forebrain organoid study (IN_VITRO) reports the 20-23% PHTS-ASD frequency in its background, citing prior human-clinical literature; classified by the publication's primary evidence type. Human-cohort confirmation is provided separately by PMID:33509259."
  - reference: PMID:33509259
    reference_title: Cross-level analysis of molecular and neurobehavioral function in a prospective series of patients with germline heterozygous PTEN mutations with and without autism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PTEN is a well-established risk gene for autism spectrum disorder (ASD)."
    explanation: "Multi-center prospective patient cohort confirms PTEN as an established ASD risk gene, supporting ASD as a Cowden/PHTS clinical phenotype."
- category: Clinical
  name: Developmental Delay and Intellectual Disability
  description: >
    Global developmental delay and intellectual disability are common neurodevelopmental
    manifestations of PHTS/Cowden syndrome, particularly in the childhood-onset
    Bannayan-Riley-Ruvalcaba end of the spectrum. In a 47-patient pediatric PHTS
    chart-review cohort, macrocephaly with developmental delay, intellectual
    disability, and/or autism spectrum disorder was the most common presenting
    finding, occurring in 66% of patients. Cognitive impairment in PTEN mutation
    carriers ranges from mild language delays to moderate-severe global cognitive
    dysfunction; impairments in general cognitive ability are most common in PTEN-ASD
    cases but neurobehavioral variability is high across the PHTS spectrum.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:17526800
    reference_title: "Cowden syndrome and Bannayan Riley Ruvalcaba syndrome represent one condition with variable expression and age-related penetrance: results of a clinical study of PTEN mutation carriers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bannayan-Riley-Ruvalcaba syndrome (BRRS), with childhood onset, macrocephaly, lipomas and developmental delay"
    explanation: "Establishes developmental delay as a defining clinical feature of the BRRS end of the PHTS spectrum (CS and BRRS are now recognised as a single PHTS condition with variable expression)."
  - reference: PMID:28526761
    reference_title: "A retrospective chart review of the features of PTEN hamartoma tumour syndrome in children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "developmental delay, ID and/or ASD were the most common presenting signs/symptoms (66 %)"
    explanation: "Quantifies the combined prevalence of developmental delay, intellectual disability, and/or ASD as the most common presenting finding in a 47-patient pediatric PHTS chart-review cohort."
  - reference: PMID:33509259
    reference_title: Cross-level analysis of molecular and neurobehavioral function in a prospective series of patients with germline heterozygous PTEN mutations with and without autism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "impairments in general cognitive ability are only common in PTEN-ASD. For most neurobehavioral measures, variability within and across patient groups was very large, with some patients functioning in the average or above average range in most neurocognitive domains and other patients showing moderate to severe global cognitive dysfunction"
    explanation: "Multi-center prospective PHTS cohort documents the spectrum of cognitive impairment, supporting global developmental delay / intellectual disability as a distinct clinical phenotype distinguishable from ASD diagnosis itself."
- category: Clinical
  name: Lipoma
  description: >
    Subcutaneous and visceral lipomas are common in PHTS/Cowden syndrome and are part
    of the diagnostic criteria. Lipomas reflect adipocyte over-proliferation driven by
    PI3K/AKT pathway hyperactivation in PTEN-haploinsufficient mesenchymal cells. They
    are particularly characteristic of the Bannayan-Riley-Ruvalcaba (childhood-onset)
    end of the PHTS spectrum but also occur in adult Cowden syndrome.
  phenotype_term:
    preferred_term: Lipoma
    term:
      id: HP:0012032
      label: Lipoma
  evidence:
  - reference: PMID:18781191
    reference_title: PTEN hamartoma tumor syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bannayan-Riley-Ruvalcaba syndrome (BRRS), characterized by the developmental delay, macrocephaly, lipomas, hemangiomas, and speckled penis in males, is associated with PTEN mutations in approximately 60% of cases."
    explanation: "Establishes lipomas as a defining clinical feature of the BRRS end of the PHTS spectrum; CS and BRRS are now recognised as one PHTS condition with variable expression, so lipomas are a Cowden-spectrum phenotype."
  - reference: PMID:40120468
    reference_title: "Spontaneous tonsillar hemorrhage in a patient with PTEN mutation: A case report and systematic literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Phosphatase and tensin homolog hamartoma tumor syndrome (PTEN Syndrome), an autosomal dominant group of disorders caused by PTEN dysregulation, predisposes patients to hamartomas, lipomas, vascular tumors/malformations, and potential malignancies."
    explanation: "Independent confirmation of lipomas as a recognised feature of the PTEN syndrome spectrum, including Cowden syndrome."
- category: Clinical
  name: Vascular Anomalies
  description: >
    Vascular anomalies — including arteriovenous malformations (AVMs), arteriovenous
    fistulas, hemangiomas, and venous malformations — are recognised features of
    PHTS/Cowden syndrome, particularly affecting the extremities and central nervous
    system. They are thought to arise from PTEN-deficient endothelial proliferation and
    PI3K/AKT pathway dysregulation in the vascular bed. Spinal and intracranial AVMs
    have been reported and may produce neurological signs. The descriptor binds to AVM
    as the most consistently reported vascular lesion in CS case series; venous
    malformations and hemangiomas are also reported but lack a single covering term.
  phenotype_term:
    preferred_term: Arteriovenous malformation
    term:
      id: HP:0100026
      label: Arteriovenous malformation
  evidence:
  - reference: PMID:39048366
    reference_title: Spinal Dural Arteriovenous Fistulas in a Patient with Cowden Syndrome and a Phosphatase and Tensin Homolog Mutation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Vascular malformations are common in CS, particularly in the extremities."
    explanation: "Direct clinical statement that vascular malformations are common in Cowden syndrome, with case-level evidence of spinal dural arteriovenous fistulas associated with a truncating PTEN mutation."
  - reference: PMID:40120468
    reference_title: "Spontaneous tonsillar hemorrhage in a patient with PTEN mutation: A case report and systematic literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "predisposes patients to hamartomas, lipomas, vascular tumors/malformations, and potential malignancies."
    explanation: "Independent statement of vascular tumors/malformations as a defining PHTS phenotype."
- category: Clinical
  name: Renal Cell Carcinoma
  description: >
    PTEN mutation carriers face a markedly elevated lifetime risk of renal cell carcinoma
    (estimated 2-34% across PHTS cohorts and surveillance guideline projections, vs.
    ~1.6% general population). KLLN-methylation (Cowden syndrome 4) carriers may have
    higher renal cancer risk than PTEN-mutation-positive patients alone. Screening renal
    ultrasound is recommended every 2 years from age 40.
  phenotype_term:
    preferred_term: Renal cell carcinoma
    term:
      id: HP:0005584
      label: Renal cell carcinoma
  evidence:
  - reference: PMID:32533092
    reference_title: Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The projected estimated lifetime risks of cancer in individuals with PHTS range from 85 to 89% for any cancer, 67 to 85% for female breast cancer, 6 to 38% for thyroid cancer, 2 to 28% for endometrial cancer, 2 to 34% for renal cancer, 9 to 20% for colorectal cancer and 0 to 6% for melanoma."
    explanation: "European expert consensus places lifetime renal cancer risk at 2-34%, motivating renal cell carcinoma as a distinct PHTS/Cowden phenotype with surveillance recommendations."
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals."
    explanation: "Identifies KLLN-methylation Cowden syndrome 4 as conferring particularly elevated renal cancer risk relative to classical PTEN-mutation cases."
- category: Clinical
  name: Colorectal Cancer
  description: >
    Lifetime colorectal cancer risk in PHTS is estimated at ~9-20%, substantially higher
    than the general-population background (~4%). Hamartomatous colon polyps are nearly
    universal in adult Cowden syndrome and may, in a subset, transform to adenomatous
    lesions and carcinoma. Baseline colonoscopy at age 35-40 with surveillance intervals
    based on findings is recommended.
  phenotype_term:
    preferred_term: Colon cancer
    term:
      id: HP:0003003
      label: Colon cancer
  evidence:
  - reference: PMID:32533092
    reference_title: Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "9 to 20% for colorectal cancer"
    explanation: "European expert consensus quantifies the elevated colorectal cancer risk (9-20% lifetime) that motivates including colorectal carcinoma as a recognised PHTS/Cowden phenotype."

biochemical:
- name: Plasma succinate
  presence: INCREASED
  context: >-
    Elevated plasma succinate is the one biochemical finding reported to be
    shared across the genetically distinct causes of Cowden and Cowden-like
    syndrome. It was found in 62% of individuals carrying a germline PTEN,
    SDHB or SDHD mutation against 16% of controls, and in 67% of those with a
    pathogenic PTEN mutation against under 20% of mutation-negative
    individuals meeting the same clinical criteria. The authors interpret it
    as reduced succinate dehydrogenase catalytic activity common to both
    genotype groups. This is a single-centre finding on small numbers, has not
    been independently replicated, and is not in clinical use; it is curated
    because it is the only proposed unifying biomarker for the PTEN-positive
    and PTEN-negative arms of this entry.
  biomarker_term:
    preferred_term: succinate
    term:
      id: CHEBI:30031
      label: succinate(2-)
  evidence:
  - reference: PMID:22261759
    reference_title: "Elevated plasma succinate in PTEN, SDHB, and SDHD mutation-positive individuals."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Elevated plasma succinate was observed in 13/21 (62%) individuals with germline PTEN, SDHB, or SDHD mutations as compared with 5/32 (16%) controls (P < 0.001), in 10/15 (67%) individuals with pathogenic PTEN mutations but in <20% of mutation-negative individuals meeting identical criteria"
    explanation: >-
      Gives the measured difference against both healthy controls and, more
      informatively, against clinically identical mutation-negative
      individuals, which is what makes it a candidate discriminating marker.
  - reference: PMID:22261759
    reference_title: "Elevated plasma succinate in PTEN, SDHB, and SDHD mutation-positive individuals."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations"
    explanation: >-
      The mechanistic interpretation, graded PARTIAL because the study measures
      the metabolite and infers the enzyme activity rather than assaying it.
  notes: >-
    Denominators are small (21 mutation carriers). Treat this as an
    observation that generates a hypothesis rather than a usable marker; see
    mechanistic_hypotheses#pten_sdhx_succinate_convergence.
genetic:
- name: PTEN
  subtype: CS1
  gene_term:
    preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  association: Causative
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    evidence:
    - reference: PMID:21194675
      reference_title: A clinical scoring system for selection of patients for PTEN mutation testing is proposed on the basis of a prospective study of 3042 probands.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome are allelic, defined by germline PTEN mutations, and collectively referred to as PTEN hamartoma tumor syndrome."
      explanation: "Establishes autosomal dominant germline PTEN mutations as the cause of Cowden syndrome: each affected generation inherits one pathogenic allele."
  notes: >
    Germline loss-of-function mutations in PTEN (MIM 601728) on chromosome 10q22-23
    are identified in approximately 80% of patients meeting strict clinical diagnostic
    criteria for Cowden syndrome. Mutations include nonsense, frameshift, missense,
    splice-site variants, and large deletions.
  evidence:
  - reference: PMID:21194675
    reference_title: A clinical scoring system for selection of patients for PTEN mutation testing is proposed on the basis of a prospective study of 3042 probands.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome are allelic, defined by germline PTEN mutations, and collectively referred to as PTEN hamartoma tumor syndrome."
    explanation: "Establishes PTEN germline mutations as the defining genetic cause of Cowden syndrome in a large prospective cohort of 3042 probands."
- name: KLLN
  subtype: CS4
  gene_term:
    preferred_term: KLLN
    term:
      id: hgnc:37212
      label: KLLN
  association: Causative
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    evidence:
    - reference: PMID:21177507
      reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals."
      explanation: "Confirms KLLN/KILLIN germline epigenetic silencing as a heritable mechanism in Cowden syndrome 4, transmitted in an autosomal dominant pattern through the PTEN-KLLN bidirectional promoter locus."
  notes: >
    Promoter hypermethylation (epimutation) or deletion of KILLIN (KLLN), a p53
    co-regulated tumor suppressor transcribed in the opposite direction from the same
    PTEN promoter, is found in approximately 37% of Cowden/Cowden-like syndrome patients
    lacking PTEN coding mutations. KLLN down-regulation by 250-fold leads to loss of
    p53-activated DNA synthesis inhibition and apoptosis, conferring higher breast and
    kidney cancer risk than PTEN mutation alone.
  evidence:
  - reference: PMID:21177507
    reference_title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals."
    explanation: "Establishes KLLN germline methylation as a distinct molecular subtype of Cowden syndrome with measurably elevated cancer risks."
- name: PIK3CA
  subtype: CS5
  gene_term:
    preferred_term: PIK3CA
    term:
      id: hgnc:8975
      label: PIK3CA
  association: Susceptibility in PTEN-negative Cowden-like syndrome
  relationship_type: SUSCEPTIBILITY
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    evidence:
    - reference: PMID:23246288
      reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Our observations suggest that PIK3CA and AKT1 are CS susceptibility genes."
      explanation: "Establishes PIK3CA germline mutations as a cause of Cowden syndrome 5 through direct activation of the PI3K/AKT pathway, with autosomal dominant inheritance."
  notes: >
    Activating germline mutations in PIK3CA (the catalytic p110alpha subunit of PI3-kinase)
    are identified in approximately 8.8% of PTEN mutation-negative Cowden/Cowden-like
    syndrome individuals and result in significantly increased phospho-AKT and cellular
    PIP3. Current nosology should treat this as PTEN-negative Cowden-like susceptibility,
    not as classic PTEN-defined Cowden syndrome. This directly activates the same
    downstream pathway affected by PTEN loss.
  case_fractions:
  - population: PTEN-mutation-negative Cowden syndrome probands, Cleveland Clinic series
    case_fraction_percent: 8.8
    cohort_size: 91
    notes: Eight of 91 unrelated PTEN-negative Cowden syndrome individuals.
    evidence:
    - reference: PMID:23246288
      reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."
      explanation: States the PIK3CA share of PTEN-negative Cowden syndrome probands.
  evidence:
  - reference: PMID:23246288
    reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."
    explanation: "Directly identifies PIK3CA germline mutations in Cowden syndrome patients lacking PTEN mutations, confirming PIK3CA as a causative gene in Cowden syndrome 5."
- name: SDHB
  subtype: CS2
  gene_term:
    preferred_term: SDHB
    term:
      id: hgnc:10681
      label: SDHB
  association: Susceptibility in PTEN-negative Cowden-like syndrome
  relationship_type: SUSCEPTIBILITY
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    evidence:
    - reference: PMID:18678321
      reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."
      explanation: "Establishes SDHB/SDHD germline mutations as heritable CS2/CS3 causes via autosomal dominant inheritance, manifesting increased breast, thyroid, and renal cancer risk."
  notes: >
    Germline SDHB or SDHD variants were found in 10 of the 74 Cowden/Cowden-like
    individuals who had raised manganese superoxide dismutase expression and no PTEN
    alteration, out of 375 PTEN-negative CS/CS-like individuals screened; three of
    those ten carried an SDHB variant and seven carried SDHD, so the 13.5% figure is
    the combined SDHx share and not SDHB's alone. Current nosology should treat this as
    PTEN-negative Cowden-like susceptibility, not as classic PTEN-defined Cowden
    syndrome. In the absence of PTEN alteration these variants raise phospho-AKT and
    phospho-MAPK, the same downstream readouts PTEN dysfunction produces.
  evidence:
  - reference: PMID:18678321
    reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."
    explanation: "Establishes SDHB germline mutations as a contributor in Cowden syndrome 2, found in PTEN-mutation-negative individuals with elevated cancer risk."
- name: SDHD
  subtype: CS3
  gene_term:
    preferred_term: SDHD
    term:
      id: hgnc:10683
      label: SDHD
  association: Susceptibility in PTEN-negative Cowden-like syndrome
  relationship_type: SUSCEPTIBILITY
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  notes: >
    The larger of the two SDHx arms of Cowden/Cowden-like syndrome. Seven of the ten
    SDHx carriers in the defining screen carried an SDHD variant, against three for
    SDHB. The same nosological caveat applies as for SDHB: this is PTEN-negative
    Cowden-like susceptibility rather than a classic PTEN-defined Cowden syndrome
    cause, and ClinGen has curated SDHD only against hereditary
    pheochromocytoma-paraganglioma (Definitive) and mitochondrial disease (Limited),
    with no Cowden assertion.
  evidence:
  - reference: PMID:18678321
    reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among these, 10 (13.5%) had germline mutations/variants in SDHB (n = 3) or SDHD (7), not found in 700 controls (p < 0.001)."
    explanation: >-
      Reports the seven SDHD carriers, absent from the 700 controls screened, that
      are the genetic evidence for this row.
  - reference: PMID:22261759
    reference_title: "Elevated plasma succinate in PTEN, SDHB, and SDHD mutation-positive individuals."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations"
    explanation: >-
      Names SDHD alongside SDHB and PTEN as reaching the succinate dehydrogenase
      node, which is where this gene is wired in the pathograph.
- name: AKT1
  subtype: CS6
  gene_term:
    preferred_term: AKT1
    term:
      id: hgnc:391
      label: AKT1
  association: Susceptibility in PTEN-negative Cowden-like syndrome
  relationship_type: SUSCEPTIBILITY
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  notes: >
    Activating germline AKT1 variants were reported in 2 of 91 PTEN-negative Cowden
    syndrome probands, in the same study that reported the PIK3CA arm, and nothing has
    been added since. ClinGen's Childhood, Adolescent and Young Adult Cancer
    Predisposition panel graded the relationship Limited in November 2024, noting that
    two missense variants in two probands in one publication are the whole genetic
    evidence base. The row is retained because AKT1 is the direct effector of the axis
    PTEN restrains, so the mechanism is shared with CS1 and CS5 even where the genetic
    evidence is not.
  case_fractions:
  - population: PTEN-mutation-negative Cowden syndrome probands, Cleveland Clinic series
    case_fraction_percent: 2.2
    cohort_size: 91
    notes: Two of 91 unrelated PTEN-negative Cowden syndrome individuals.
    evidence:
    - reference: PMID:23246288
      reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We report that 8 of 91 (8.8%) unrelated CS individuals without germline PTEN mutations carried 10 germline PIK3CA mutations (7 missense, 1 nonsense, and 2 indels) and 2 (2.2%) AKT1 mutations. These mutations result in significantly increased P-Thr308-AKT and increased cellular PIP3."
      explanation: States the AKT1 share of PTEN-negative Cowden syndrome probands.
  evidence:
  - reference: PMID:23246288
    reference_title: Germline PIK3CA and AKT1 mutations in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our observations suggest that PIK3CA and AKT1 are CS susceptibility genes."
    explanation: The authors' own statement of the relationship, in the hedged form they give it.
  - reference: CGGV:assertion_1333bd6d-332b-4c75-8811-cde8efce2001-2024-11-12T170000.000Z
    reference_title: AKT1 / Cowden syndrome 6 (Limited)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "AKT1 | HGNC:391 | Cowden syndrome 6 | MONDO:0014048 | AD | Limited | SOP11"
    explanation: >-
      The ClinGen gene-disease validity row for this exact subtype concept, giving
      the Limited classification this record is qualified by.
- name: SEC23B
  subtype: CS7
  gene_term:
    preferred_term: SEC23B
    term:
      id: hgnc:10702
      label: SEC23B
  association: Susceptibility in PTEN-negative Cowden syndrome
  relationship_type: SUSCEPTIBILITY
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  notes: >
    The evidence is a single multi-generation Cowden family in which a missense SEC23B
    variant segregated with the phenotype, plus 3 of 96 unrelated PTEN-negative Cowden
    probands with thyroid cancer, from one 2015 report. No independent replication has
    been published. The proposed mechanism is endoplasmic reticulum stress rather than
    PI3K/AKT activation, which makes this the one subtype gene that does not converge
    on the pathway the other six share. ClinGen has curated SEC23B only against
    congenital dyserythropoietic anemia type 2, the recessive disorder biallelic
    variants cause, with no Cowden assertion. The absence of replication is a recorded
    search, not an assumption: PubMed for SEC23B Cowden syndrome returns two records,
    the 2015 report itself and a 2016 familial non-medullary thyroid cancer review
    (PMID:27807061) that cites it, and the ClinGen gene-validity download holds no
    SEC23B Cowden row.
  case_fractions:
  - population: PTEN-mutation-negative Cowden syndrome probands with thyroid cancer
    case_fraction_percent: 3.0
    cohort_size: 96
    notes: Three of 96 unrelated PTEN-negative Cowden probands with thyroid cancer.
    evidence:
    - reference: PMID:26522472
      reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We also found germline heterozygous SEC23B variants in 3/96 (3%) unrelated mutation-negative CS probands with thyroid cancer and in The Cancer Genome Atlas (TCGA), representing apparently sporadic cancers."
      explanation: States the SEC23B share of PTEN-negative Cowden probands with thyroid cancer.
  evidence:
  - reference: PMID:26522472
    reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "By characterizing the p.Val594Gly variant in a normal thyroid cell line, we show that it is a functional alteration that results in ER-stress-mediated cell-colony formation and survival, growth, and invasion, which reflect aspects of a cancer phenotype."
    explanation: >-
      The functional support for the index family's variant, obtained in a thyroid
      cell line rather than in patient tissue.
  - reference: PMID:26522472
    reference_title: Germline Heterozygous Variants in SEC23B Are Associated with Cowden Syndrome and Enriched in Apparently Sporadic Thyroid Cancer.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "Interestingly, germline homozygous or compound-heterozygous SEC23B mutations cause an unrelated disorder, congenital dyserythropoietic anemia type II, and SEC23B-deficient mice suffer from secretory organ degeneration due to ER-stress-associated apoptosis."
    explanation: >-
      Records that the established SEC23B disease is a different, recessive disorder,
      which is why the Cowden relationship is carried here as unreplicated.

diagnosis:
- name: Clinical Cowden syndrome diagnostic criteria
  description: >
    Clinical diagnosis should apply the Cowden syndrome pathognomonic, major, and
    minor criteria before or alongside molecular testing. Pathognomonic criteria
    include adult Lhermitte-Duclos disease and characteristic mucocutaneous lesions
    such as multiple facial trichilemmomas, oral mucosal papillomatosis with acral
    keratoses, or multiple palmoplantar keratoses. Major criteria include breast
    cancer, non-medullary thyroid cancer, macrocephaly, and endometrial carcinoma.
    Minor criteria include other thyroid lesions, intellectual disability,
    hamartomatous intestinal polyps, lipomas, fibromas, genitourinary tumors
    including renal cell carcinoma, genitourinary malformations, and uterine
    fibroids. A clinical diagnosis is met by a pathognomonic mucocutaneous pattern,
    two or more major criteria, one major plus at least three minor criteria, or
    four or more minor criteria.
  diagnosis_term:
    preferred_term: clinical assessment
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  evidence:
  - reference: 'url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable'
    reference_title: "PTEN Hamartoma Tumor Syndrome - GeneReviews® - NCBI Bookshelf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Consensus clinical diagnostic criteria have been divided into three categories: pathognomonic, major, and minor."
    explanation: GeneReviews provides the pathognomonic/major/minor clinical criteria framework for Cowden syndrome.
  - reference: 'url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable'
    reference_title: "PTEN Hamartoma Tumor Syndrome - GeneReviews® - NCBI Bookshelf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "A clinical diagnosis of CS</b> is established if an individual meets <b>any one</b> of the following criteria:"
    explanation: GeneReviews supports applying rule-based clinical diagnostic combinations before or alongside molecular confirmation.
- name: PTEN molecular genetic testing cascade
  description: >
    Molecular confirmation of classic PHTS/Cowden syndrome is by identifying a
    heterozygous germline pathogenic PTEN variant. Testing should start with PTEN
    sequence analysis, then deletion/duplication analysis if sequencing is negative,
    and PTEN promoter sequencing if no pathogenic variant is found. If the phenotype
    remains Cowden-like without a PTEN finding, consider Cowden-like susceptibility
    mechanisms such as KLLN epimutation, SDHx, PIK3CA, AKT1, SEC23B, and WWP1 rather
    than treating them as equivalent to classic PTEN Cowden syndrome.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  evidence:
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of PHTS is established in a proband by identification of a heterozygous germline PTEN pathogenic variant on molecular genetic testing."
    explanation: GeneReviews establishes heterozygous germline PTEN pathogenic variation as the molecular diagnostic basis for PHTS.
  - reference: 'url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable'
    reference_title: "PTEN Hamartoma Tumor Syndrome - GeneReviews® - NCBI Bookshelf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Sequence analysis of <i>PTEN</i> is performed first and followed by gene-targeted deletion/duplication analysis if no pathogenic variant is found."
    explanation: GeneReviews supports the PTEN sequence-first, deletion/duplication-second testing cascade.
  - reference: 'url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable'
    reference_title: "PTEN Hamartoma Tumor Syndrome - GeneReviews® - NCBI Bookshelf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Susceptibility genes in individuals with non-PHTS CS and CLS."
    explanation: GeneReviews separates non-PHTS Cowden/Cowden-like susceptibility genes from classic PTEN-defined PHTS.
- name: Testing and counseling of at-risk relatives
  description: >
    Once a familial PTEN pathogenic variant is identified, asymptomatic at-risk
    relatives should be offered molecular testing so that carriers can enter organ-specific
    surveillance and non-carriers can avoid unnecessary PHTS surveillance.
    Counseling should cover autosomal dominant inheritance, incomplete clinical
    recognition, cancer risks, reproductive options, and the need for surveillance
    beginning before many cancers develop.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  evidence:
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When a PTEN pathogenic variant has been identified in a proband, molecular genetic testing of asymptomatic at-risk relatives can identify those who have the family-specific pathogenic variant and warrant ongoing surveillance."
    explanation: GeneReviews supports familial variant testing to determine which relatives need PHTS surveillance.
treatments:
- name: Enhanced Cancer Surveillance
  description: >
    PTEN mutation carriers require life-long intensified surveillance protocols.
    GeneReviews and ERN GENTURIS support organ-specific surveillance that includes
    breast awareness and clinical examination, annual breast MRI beginning around
    age 30 with mammography incorporated by age 40, yearly thyroid ultrasound,
    dermatologic evaluation, baseline colonoscopy at age 35-40 with intervals based
    on findings, renal imaging from age 40, and earlier screening 5-10 years before
    the youngest cancer in a family when family history indicates. Endometrial
    surveillance should be framed as consideration rather than universal screening:
    GeneReviews recommends considering screening by age 35 with endometrial biopsy
    every 1-2 years and/or postmenopausal transvaginal ultrasound at clinician
    discretion, while ERN GENTURIS notes weak evidence and recommends symptom
    education or clinical-trial-based screening.
  treatment_term:
    preferred_term: cancer surveillance
    term:
      id: NCIT:C15406
      label: Cancer Screening
  evidence:
  - reference: PMID:32533092
    reference_title: Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recommendations were put forward for surveillance for breast, thyroid and renal cancers. Limited recommendations were developed for other sites including endometrial, colon and skin."
    explanation: "Provides evidence-based surveillance recommendations for PHTS/Cowden syndrome from the European Reference Network for Genetic Tumour Risk Syndromes."
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Women beginning at age 30 years. Monthly breast self-examination; annual breast screening (at minimum mammogram; MRI may also be incorporated). Starting by age 35 years, consider transvaginal ultrasound or endometrial biopsy."
    explanation: GeneReviews supports breast screening from age 30 and consideration of endometrial screening from age 35.
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Men and women. Colonoscopy beginning at age 35 years with frequency dependent on degree of polyposis identified or family history of early-onset colon cancer (before age 40); biennial (every 2 years) renal imaging (CT or MRI preferred) beginning at age 40 years."
    explanation: GeneReviews supports colorectal and renal surveillance age/interval guidance.
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Adults. Yearly thyroid ultrasound and dermatologic evaluation."
    explanation: GeneReviews supports yearly thyroid and dermatologic surveillance in adults.
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Those with a family history of a particular cancer type at an early age. Consider initiating screening 5 to 10 years prior to the youngest age of diagnosis in the family."
    explanation: GeneReviews supports earlier family-history-driven surveillance starts.
  review_notes: >-
    Deliberately carries no target_mechanisms. Surveillance does not act on any
    mechanism in this entry - it shifts when disease is detected, and dismech
    has no predicate for that. An edge labelled MODULATES would assert that it
    alters the mechanism, which is the opposite of what this treatment does.
    It reaches the pathograph through
    discussions#cs_surveillance_effectiveness, which attaches to it.

- name: Prophylactic Mastectomy
  description: >
    Risk-reducing bilateral mastectomy reduces breast cancer risk by more than 90% in
    PTEN mutation carriers with high personal or family risk. It is offered as an option
    after careful counseling regarding elevated lifetime risk, using the same approach
    as for BRCA1/BRCA2 carriers.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: prophylactic mastectomy
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: PMID:32533092
    reference_title: Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Risk reduction surgery should be offered using the same considerations as for women with germline BRCA1/BRCA2 pathogenic variants"
    explanation: "Supports offering prophylactic mastectomy in PTEN mutation carriers following the same approach as for BRCA1/BRCA2, given comparable breast cancer risk levels."
  target_mechanisms:
  - target: Increased Cancer Risk
    treatment_effect: INHIBITS
    description: >-
      Unlike surveillance, risk-reducing mastectomy removes the tissue in which
      the PTEN-driven breast cancer risk is realised, so it acts on the node by
      removing its substrate rather than by detecting its output earlier. It
      addresses one organ of several, which is why it does not displace the
      surveillance programme.
    evidence:
    - reference: PMID:23335809
      reference_title: High cumulative risks of cancer in patients with PTEN hamartoma tumour syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Cumulative cancer risks at age 70 were 85% (95% CI 70% to 95%) for any cancer, 77% (95% CI 59% to 91%) for female breast cancer, and 38% (95% CI 25% to 56%) for thyroid cancer."
      explanation: >-
        The magnitude of the breast-cancer risk that makes removing the tissue
        a proportionate intervention.

- name: mTOR Inhibitor Therapy
  description: >
    Everolimus (RAD001), an mTORC1 inhibitor, targets the hyperactivated PI3K/AKT/mTOR
    pathway in Cowden syndrome. The mechanistic rationale stems directly from PTEN loss
    driving constitutive mTOR activation. A 6-month phase II placebo-controlled randomised
    trial of everolimus in 46 PHTS individuals (5-45 years) demonstrated that the drug is
    well tolerated; the primary neurocognitive endpoint was not met but several secondary
    neurobehavioral measures and EEG biomarkers showed signals of improvement, supporting
    continued investigation rather than routine clinical use.
  treatment_term:
    preferred_term: mTOR inhibitor pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: mTOR inhibitor
      term:
        id: NCIT:C2201
        label: mTOR Inhibitor
    - preferred_term: everolimus
      term:
        id: CHEBI:68478
        label: everolimus
  evidence:
  - reference: PMID:35594551
    reference_title: A randomized controlled trial of everolimus for neurocognitive symptoms in PTEN hamartoma tumor syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PTEN hamartoma tumor syndrome (PHTS) is a complex neurodevelopmental disorder characterized by mechanistic target of rapamycin (mTOR) overactivity. Limited data suggest that mTOR inhibitors may be therapeutic."
    explanation: "Establishes the mechanistic rationale (mTOR overactivity) and motivates the placebo-controlled trial of everolimus in PHTS that this paper reports."
  - reference: PMID:35594551
    reference_title: A randomized controlled trial of everolimus for neurocognitive symptoms in PTEN hamartoma tumor syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Everolimus is well tolerated in PHTS; adverse events were similar to previous reports. The primary efficacy endpoint did not reveal improvement."
    explanation: "Phase II RCT (n=46) shows everolimus is well tolerated in PHTS but did not meet its primary neurocognitive endpoint. Supports `PARTIAL`: pharmacology supports the mTOR-inhibition rationale, but no confirmed cognitive benefit yet — clinical use remains investigational."
  - reference: PMID:18781191
    reference_title: PTEN hamartoma tumor syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Concomitant with improved understanding of the biology of PTEN and the PI3K/Akt/mTOR pathway, inhibitors of this pathway are being developed as anticancer agents. These medications could have applications for patients with PHTS, for whom no medical options currently exist."
    explanation: "Originally established the rationale for mTOR/PI3K inhibitor therapy in PHTS based on the underlying molecular mechanism (expert review, predates clinical trial data)."
  target_mechanisms:
  - target: PTEN Loss and PI3K/AKT/mTOR Pathway Activation
    treatment_effect: INHIBITS
    description: >-
      Everolimus inhibits mTORC1 directly, acting on the de-repressed limb of
      the pathway rather than restoring PTEN. This is the only
      mechanism-directed treatment in the entry; every other entry here detects
      or removes disease rather than acting on the mechanism. Whether the
      inhibition translates into clinical benefit is unsettled - the one
      randomised trial missed its primary neurocognitive endpoint - so the
      edge records what the drug does, not that it works. See
      discussions#cs_mtor_inhibition_endpoint_choice.
    evidence:
    - reference: PMID:35594551
      reference_title: A randomized controlled trial of everolimus for neurocognitive symptoms in PTEN hamartoma tumor syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "PTEN hamartoma tumor syndrome (PHTS) is a complex neurodevelopmental disorder characterized by mechanistic target of rapamycin (mTOR) overactivity. Limited data suggest that mTOR inhibitors may be therapeutic."
      explanation: >-
        States the target and the overactivity it acts on. PARTIAL because the
        same trial did not demonstrate benefit on its primary endpoint.
- name: Genetic Counseling
  description: >
    Genetic counseling is recommended for all patients with suspected or confirmed
    Cowden syndrome and their at-risk family members, informing testing decisions,
    cancer risks, and surveillance strategies.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:31433956
    reference_title: The Clinical Spectrum of PTEN Mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Timely diagnosis and understanding the natural history of PHTS are vital because early recognition enables gene-informed management, particularly as related to high-risk cancer surveillance and addressing the neurodevelopmental symptoms."
    explanation: "Highlights the importance of genetic diagnosis enabling gene-informed counseling and management in PHTS/Cowden syndrome."

animal_models:
- name: Epithelial-specific Pten deletion (colorectal juvenile polyposis)
  species: Mouse
  genotype: Intestinal-epithelium-specific conditional Pten deletion
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  description: >-
    Conditional deletion of Pten restricted to the colorectal epithelium. It
    is the first model to reproduce the colorectal juvenile polyposis of
    Cowden syndrome, and it settled a mechanistic question the human material
    could not: juvenile polyps had been attributed to somatic PTEN loss in the
    stroma, and this model shows epithelial loss alone is sufficient, with the
    stromal changes appearing as a consequence.
  publication: PMID:24200851
  modeled_mechanisms:
  - target: Hamartoma Formation
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Reproduces the full histopathology of Cowden colorectal juvenile polyps,
      including the stromal alterations and progression to invasive carcinoma.
    limitations: >-
      Single-tissue conditional model: it captures the colorectal
      manifestation and says nothing about the multi-system distribution of
      hamartomas that defines the syndrome clinically. Polyps form only after
      a long latency, so timing does not map onto the human course.
    readouts:
    - name: Colorectal juvenile polyp formation and dysplastic transformation
      target: Hamartoma Formation
      direction: INCREASED
      interpretation: >-
        Histopathological readout matched feature-by-feature against human
        Cowden juvenile polyps.
      evidence:
      - reference: PMID:24200851
        reference_title: "Epithelial-specific loss of PTEN results in colorectal juvenile polyp formation and invasive cancer."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "we find that these lesions closely recapitulate all of the characteristic histopathological features of juvenile polyps seen in patients with CS, including stromal alterations and dysplastic transformation to colorectal carcinoma"
        explanation: >-
          States the histopathological correspondence with human Cowden polyps
          that grounds the RECAPITULATES grading.
  evidence:
  - reference: PMID:24200851
    reference_title: "Epithelial-specific loss of PTEN results in colorectal juvenile polyp formation and invasive cancer."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our transgenic model is the first to recapitulate colorectal juvenile polyposis in patients with CS. We conclude that stromal PTEN loss is not a prerequisite for the formation of juvenile polyps, and that colorectal juvenile polyps in CS are bona fide neoplastic precursor lesions."
    explanation: >-
      Establishes both that the model is informative for the human lesion and
      the specific mechanistic conclusion it supports.
- name: Neuronal Pten deletion (macrocephaly and social-behaviour phenotypes)
  species: Mouse
  genotype: Neuron-specific Pten deletion or mutation
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  description: >-
    Neuron-restricted Pten loss produces enlarged neuronal soma, dendritic
    hypertrophy, increased synaptic density, altered long-term potentiation
    and depression, and deficits in learning, memory and social behaviour.
    These are the cellular substrates of the macrocephaly and autism-spectrum
    features of Cowden syndrome, and they connect the entry's
    Neurodevelopmental Cortical Dysfunction node to measurable synaptic
    physiology rather than only to organoid morphology.
  publication: PMID:39812527
  modeled_mechanisms:
  - target: Neurodevelopmental Cortical Dysfunction
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces neuronal hypertrophy, altered synaptic plasticity, and social
      and learning deficits following Pten loss in neurons.
    limitations: >-
      Most published models delete Pten in neurons rather than modelling
      germline heterozygosity, so gene dosage is more severe than in patients.
      Rodent social-behaviour assays are proxies for human autism-spectrum
      features rather than measurements of them, and the evidence cited here
      is a review synthesising several models rather than one primary study.
    readouts:
    - name: Neuronal soma size, dendritic arborisation and synaptic density
      target: Neurodevelopmental Cortical Dysfunction
      direction: INCREASED
      interpretation: >-
        Structural correlates of macrocephaly and altered connectivity in
        Pten-deficient neurons.
      evidence:
      - reference: PMID:39812527
        reference_title: "The integral role of PTEN in brain function: from neurogenesis to synaptic plasticity and social behavior."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Animal models with PTEN deletion or mutation exhibit significant structural and functional neuronal abnormalities, including enlarged soma and dendritic hypertrophy, increased synaptic density"
        explanation: >-
          Lists the measured structural and electrophysiological readouts
          across Pten models.
  evidence:
  - reference: PMID:39812527
    reference_title: "The integral role of PTEN in brain function: from neurogenesis to synaptic plasticity and social behavior."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These changes lead to deficits in learning and memory tasks, as well as impairments in social behaviors. PTEN mutations are associated with neurodevelopmental disorders like intellectual disability, epilepsy, and autism spectrum disorders accompanied by macrocephaly."
    explanation: >-
      Connects the model phenotypes to the human neurodevelopmental features,
      which is what makes the models informative for this node.
- name: Mammary Pten loss with constitutive Stat5 activation
  species: Mouse
  genotype: Mammary Pten loss of function with constitutively active Stat5; conditional mammary Stat5 ablation as the intervention arm
  genes:
  - preferred_term: PTEN
    term:
      id: hgnc:9588
      label: PTEN
  - preferred_term: STAT5A
    term:
      id: hgnc:11366
      label: STAT5A
  description: >-
    The breast arm, which the entry's other two models do not reach. Breast
    cancer is the largest single risk in Cowden syndrome, and this is the model
    the source describes as a genuine mouse model for it. Constitutive Stat5
    activation cooperates with Pten loss to accelerate preneoplastic lesions
    and mammary tumours; the mechanism offered is that Stat5 drives
    transcription of Akt1 and of both PI3K subunits, so the two lesions
    converge on the same prosurvival pathway from different directions. The
    interventional arm is the informative part: mammary-specific Stat5 ablation
    prevents carcinogenesis in that background, which makes the cooperation a
    dependency rather than an association.
  publication: PMID:24469394
  modeled_mechanisms:
  - target: Increased Cancer Risk
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces PTEN-driven mammary carcinogenesis, the largest organ-specific
      risk in the syndrome, and identifies a pathway dependency that can be
      removed to prevent it.
    limitations: >-
      Tumour acceleration requires constitutive Stat5 activation alongside Pten
      loss, which is an engineered cooperating lesion rather than something
      Cowden syndrome patients carry, so the model reports on a sensitised
      background rather than on germline PTEN heterozygosity alone. It is a
      single-organ model and says nothing about the thyroid, endometrial or
      renal risks, and the prevention result is a genetic ablation, not a drug.
    readouts:
    - name: Preneoplastic lesion and mammary tumour formation
      target: Increased Cancer Risk
      direction: ABOLISHED
      interpretation: >-
        Mammary-specific Stat5 ablation prevents carcinogenesis in the
        Pten-deficient background. ABOLISHED rather than DECREASED because the
        source says prevented, not reduced.
      evidence:
      - reference: PMID:24469394
        reference_title: "Stat5 regulates the phosphatidylinositol 3-kinase/Akt1 pathway during mammary gland development and tumorigenesis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The mammary gland-specific ablation of Stat5 is sufficient to prevent mammary carcinogenesis in a genuine mouse model for Cowden syndrome."
        explanation: >-
          The interventional result, in the source's own words, including its
          own claim that the background is a genuine Cowden syndrome model.
  evidence:
  - reference: PMID:24469394
    reference_title: "Stat5 regulates the phosphatidylinositol 3-kinase/Akt1 pathway during mammary gland development and tumorigenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "we observed that the constitutive activation of Stat5 cooperates with the loss of function of the tumor suppressor PTEN by accelerating the formation of preneoplastic lesions and mammary tumors"
    explanation: >-
      Establishes what the model does and that Pten loss is the operative
      lesion, which is what makes it informative for the cancer-risk node.
  notes: >-
    The source proposes Jak2/Stat5 inhibition as a breast-cancer prevention
    strategy in PTEN mutation carriers. That is a hypothesis from a mouse
    model, not a treatment, and it is deliberately not curated in treatments:.
experimental_models:
- name: PTEN-mutant iPSC-derived forebrain organoids
  experimental_model_type: ORGANOID
  description: >-
    Forebrain organoids differentiated from gene-edited isogenic iPSCs carrying
    one of two germline PTEN missense alleles - G132D, associated with autism,
    and M134R, associated with cancer. The entry already cited this work as
    evidence on the neurodevelopmental node; it is modelled here as a system so
    the node carries the fidelity and limitations of the evidence, not only its
    conclusion. Its distinctive value is stage resolution, and the finding that
    resolution produced: the two alleles do not act at the same point. G132D
    disrupts neuroectoderm formation within the first several days, while M134R
    is morphologically normal then and diverges only later. Both converge on
    disrupted differentiation, radial glia positioning and cortical layering by
    72+ days. This is human tissue, which the mouse models are not.
  publication: PMID:38030818
  modeled_mechanisms:
  - target: Neurodevelopmental Cortical Dysfunction
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Human germline-PTEN-genotype cells reproduce disrupted neuronal
      differentiation, radial glial positioning and cortical layering during
      early forebrain development.
    limitations: >-
      Organoids lack vasculature, microglia and the full complement of
      inter-areal connectivity, so behavioural and circuit-level consequences
      cannot be read out at all. The two alleles also diverge on different
      timescales, and the entry should not be read as giving one window: the
      ASD-associated PTEN G132D allele disrupts neuroectoderm formation within
      the first several days of organoid generation, whereas the M134R allele
      associated with cancer looks like wild type at that stage and only
      diverges by 72+ days. Both windows correspond to fetal development, not
      to the postnatal period in which macrocephaly and autism-spectrum
      features are recognised clinically.
    readouts:
    - name: Neuronal differentiation, radial glial positioning and cortical layering
      target: Neurodevelopmental Cortical Dysfunction
      direction: ALTERED
      interpretation: >-
        Morphological readouts scored in PTEN-mutant versus isogenic control
        organoids at matched differentiation stages.
      evidence:
      - reference: PMID:38030818
        reference_title: "Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "we observed disrupted neuronal differentiation, radial glia positioning, and cortical layering in both PTEN-mutant organoids at the later stage of 72+ days of development."
        explanation: >-
          Names the three measured readouts and the differentiation stage at
          which they diverge.
  - target: PTEN Loss and PI3K/AKT/mTOR Pathway Activation
    relationship: RESCUES
    fidelity: MODERATE
    description: >-
      Pharmacological AKT inhibition with perifosine reduced over-activated AKT
      and partially corrected the cellular disorganisation in PTEN G132D
      organoids. This is the entry's only demonstration that the downstream
      pathway state, rather than PTEN itself, is what produces the cellular
      phenotype - and it is in human tissue.
    limitations: >-
      Correction was partial, not complete, and was shown for the G132D allele
      only. Perifosine is not a Cowden syndrome treatment and the experiment
      says nothing about clinical benefit; it is a mechanistic rescue, and the
      one randomised trial of pathway inhibition in patients missed its primary
      endpoint.
    readouts:
    - name: AKT activation and cellular organisation after perifosine
      target: PTEN Loss and PI3K/AKT/mTOR Pathway Activation
      direction: RESTORED
      interpretation: >-
        Over-activated AKT falls and the disrupted cellular organisation is
        partially corrected, in the same organoid system that showed the
        defect.
      evidence:
      - reference: PMID:38030818
        reference_title: "Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "Perifosine, an AKT inhibitor, reduced over-activated AKT and partially corrected the abnormalities in cellular organization observed in PTENG132D organoids."
        explanation: >-
          Reports both measured quantities - AKT activation and cellular
          organisation - and states the correction was partial.
    evidence:
    - reference: PMID:38030818
      reference_title: "Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Single cell RNAseq analyses on early-stage organoids revealed that genes related to neural cell fate were decreased in PTENG132D mutant organoids, and AKT inhibition was capable of upregulating gene signatures related to neuronal cell fate and CNS maturation pathways."
      explanation: >-
        Establishes the model as informative for the pathway-activation node,
        on a separate measurement from the readout below: inhibiting AKT moves
        the transcriptional programme, not only the cellular morphology. The
        two layers make different claims and now rest on different sentences.
  evidence:
  - reference: PMID:38030818
    reference_title: "Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We generated forebrain organoid cultures from gene-edited isogenic human induced pluripotent stem cells (hiPSCs) harboring a PTENG132D (ASD) or PTENM134R (cancer) mutant allele to model how these mutations interrupt neurodevelopmental processes."
    explanation: >-
      States what the model is and that it was built to model germline PTEN
      disruption of neurodevelopment, which is the claim a link-level evidence
      item should make. The isogenic design is what makes the genotype, rather
      than donor background, the variable under study.
inheritance:
- name: Autosomal dominant inheritance with age-dependent incomplete penetrance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: INCOMPLETE
  expressivity: VARIABLE
  description: >-
    Cowden syndrome is inherited as an autosomal dominant trait, and each child
    of an affected individual has a 50% chance of inheriting the variant.
    Most cases are simplex - no known affected relative - but that is not the
    same as de novo, and GeneReviews declines to put a number on the split
    because the condition is underdiagnosed; perhaps 10-50% of individuals have
    an affected parent. Penetrance is high but incomplete and strongly
    age-dependent, which is why cumulative lifetime cancer risk is the
    meaningful risk statement for this entry and a cross-sectional figure is
    not. Expressivity is variable even within a single family: the same
    germline PTEN variant can present as isolated macrocephaly with autism in
    one relative and as early breast or thyroid cancer in another. Sex modifies
    expression: breast and endometrial risk apply to female carriers, so a
    single "any cancer" lifetime figure conceals a large difference between
    sexes.
  evidence:
  - reference: PMID:23335809
    reference_title: High cumulative risks of cancer in patients with PTEN hamartoma tumour syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cumulative cancer risks at age 70 were 85% (95% CI 70% to 95%) for any cancer, 77% (95% CI 59% to 91%) for female breast cancer, and 38% (95% CI 25% to 56%) for thyroid cancer."
    explanation: >-
      Risks are reported as cumulative to age 70, which is the operational
      expression of age-dependent penetrance.
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Each  child of an affected individual has a 50% chance of inheriting the pathogenic  variant and developing PHTS."
    explanation: >-
      The GeneReviews transmission-risk statement, which is the baseline this
      block should carry.
  - reference: PMID:20301661
    reference_title: "PTEN Hamartoma Tumor Syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Because  CS is likely underdiagnosed, the actual proportion of simplex cases (defined as  individuals with no obvious family history) and familial cases (defined as ≥2  related affected individuals) cannot be determined. The majority of CS cases are  simplex. Perhaps 10%-50% of individuals with CS have an affected parent."
    explanation: >-
      GeneReviews explicitly declines to quantify the simplex/familial split.
      Quoted at length because the hedge is the substance: an earlier draft of
      this block asserted that a substantial proportion of cases are de novo,
      which this source does not support and which conflates simplex with
      de novo.
mechanistic_hypotheses:
- hypothesis_group_id: pten_sdhx_succinate_convergence
  hypothesis_label: PTEN loss and SDHx variants converge on reduced succinate dehydrogenase activity
  status: EMERGING
  description: >-
    Cowden and Cowden-like syndrome have genetically unrelated causes: PTEN
    loss of function, KLLN promoter hypermethylation, and SDHB/SDHD variants.
    This hypothesis proposes they converge biochemically, on reduced succinate
    dehydrogenase catalytic activity and consequent succinate accumulation. It
    matters because it would explain why clinically indistinguishable patients
    carry unrelated genotypes, and because it would give the PTEN-negative arm
    a mechanism rather than a list of candidate genes. The supporting data are
    one study of 21 mutation carriers. The proposed direction - that PTEN loss
    reduces SDH activity - has not been tested directly; the study measured the
    metabolite and inferred the enzyme.
  evidence:
  - reference: PMID:22261759
    reference_title: "Elevated plasma succinate in PTEN, SDHB, and SDHD mutation-positive individuals."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations"
    explanation: >-
      The hypothesis in the authors' own words, with their own hedge. PARTIAL
      because it is an inference from a metabolite measurement in a small
      single-centre series.
  - reference: PMID:18678321
    reference_title: Germline mutations and variants in the succinate dehydrogenase genes in Cowden and Cowden-like syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Germline SDH mutations/variants occur in a subset of PTEN mutation-negative CS/CS-like individuals and are associated with increased frequencies of breast, thyroid, and renal cancers beyond those conferred by germline PTEN mutations."
    explanation: >-
      Establishes the two genotype groups whose convergence the hypothesis
      proposes, and notes their cancer spectra differ - which the convergence
      hypothesis must eventually explain rather than assume away.
  notes: >-
    Not independently replicated. Recorded as EMERGING rather than ALTERNATIVE
    because it is not a competing account of the same data but a proposed
    extension covering cases the canonical PI3K/AKT/mTOR model does not reach.
discussions:
- discussion_id: cs_surveillance_effectiveness
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Does the intensive multi-organ surveillance this entry recommends actually
    reduce cancer mortality in PTEN hamartoma tumour syndrome?
  attaches_to:
  - treatments#Enhanced Cancer Surveillance
  rationale: >-
    The surveillance programme is the central management recommendation of the
    entry and of the European guideline behind it, and it asks a great deal of
    patients - annual imaging across several organ systems, beginning young and
    continuing for life. The guideline that recommends it states that its
    effectiveness needs prospective evaluation. So the strongest treatment
    recommendation in this entry rests on the size of the underlying cancer
    risk plus the general case for early detection, not on evidence that this
    programme changes outcomes. Curators should not upgrade the treatment's
    evidence grading on the strength of guideline endorsement alone.
  evidence:
  - reference: PMID:42463809
    reference_title: "ERN GENTURIS cancer surveillance guideline for individuals with PTEN hamartoma tumour syndrome (PHTS)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "There is a need for prospective evaluation of the effectiveness of these recommendations in the PHTS population."
    explanation: >-
      The guideline stating, in its own words, that the effectiveness of the
      recommendations it issues has not been evaluated prospectively. This is
      the claim the discussion turns on.
  - reference: PMID:42463809
    reference_title: "ERN GENTURIS cancer surveillance guideline for individuals with PTEN hamartoma tumour syndrome (PHTS)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The proposed cancer surveillance recommendations for PHTS require significant patient commitment as well as a coordinated multidisciplinary medical approach."
    explanation: >-
      Sources the burden half of the rationale. The combination - a demanding
      programme whose effectiveness the issuing guideline says is unevaluated -
      is what makes this a knowledge gap rather than a note.
- discussion_id: cs_mtor_inhibition_endpoint_choice
  kind: CONTROVERSY
  status: OPEN
  prompt: >-
    Did the everolimus trial show mTOR inhibition does not work in Cowden
    syndrome, or that neurocognition was the wrong endpoint to test it on?
  attaches_to:
  - treatments#mTOR Inhibitor Therapy
  - clinical_trials#NCT02991807
  rationale: >-
    The one randomised trial of mTOR inhibition in this disease missed its
    primary neurocognitive endpoint, in 46 participants over six months. It is
    frequently read as a negative result for the drug class. That reading may
    be too broad. The trial tested neurocognition, a phenotype set during
    fetal and early postnatal development, and asked a six-month adult and
    paediatric course of drug to move it. The hamartoma burden - a lesion that
    is actively proliferating and therefore plausibly mTOR-dependent in real
    time - was not the endpoint, and the striking anecdotal responses in
    Lhermitte-Duclos disease are in that second category. This entry records
    the trial result as PARTIAL rather than REFUTE for that reason.
  evidence:
  - reference: PMID:35594551
    reference_title: A randomized controlled trial of everolimus for neurocognitive symptoms in PTEN hamartoma tumor syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Everolimus is well tolerated in PHTS; adverse events were similar to previous reports. The primary efficacy endpoint did not reveal improvement."
    explanation: >-
      The negative primary endpoint that this controversy is about.
  - reference: PMID:27932596
    reference_title: Infantile Lhermitte-Duclos Disease Treated Successfully With Rapamycin.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rapamycin should be considered in cases of Lhermitte-Duclos disease where surgical removal may not be an option"
    explanation: >-
      A single case, so it settles nothing, but it is a response on a lesion
      endpoint rather than a cognitive one, which is the distinction this
      discussion turns on.
- discussion_id: cs_genotype_phenotype_replication
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Are the reported PTEN variant-class to organ-risk correlations real enough
    to stratify surveillance by?
  attaches_to:
  - genetic#PTEN
  rationale: >-
    Correlations have been reported between PTEN variant class and organ risk,
    with promoter variants linked to breast cancer and nonsense variants to
    colorectal cancer, and catalytically inactive but stable missense mutants
    reported as producing the most severe phenotypes. If they hold, they would
    let surveillance intensity be matched to variant class instead of applied
    uniformly, which directly affects the burden question raised in
    discussions#cs_surveillance_effectiveness. They are currently associations
    from individual cohorts without independent replication, and this entry
    does not act on them. Recorded so that a future curator finds the open
    question rather than re-deriving it.
  evidence:
  - reference: PMID:36634299
    reference_title: Cancer Risk Associated With PTEN Pathogenic Variants Identified Using Multigene Hereditary Cancer Panel Testing.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We demonstrate that PTEN PVs are associated with significantly increased risk for a range of cancers."
    explanation: >-
      A large, less ascertainment-biased cohort establishing the organ risks at
      gene level. It does not resolve the variant-class question, which is why
      the gap stands.
clinical_trials:
- name: NCT02991807
  phase: PHASE_II
  status: COMPLETED
  description: >
    A six-month randomized, double-blind, placebo-controlled phase II trial of
    everolimus (RAD001) in 46 individuals (5-45 years) with PTEN mutations,
    examining safety and efficacy on neurocognitive and behavioral outcomes
    in PHTS. Reported in Srivastava et al. 2022 (PMID:35594551). The primary
    neurocognitive endpoint was not met; everolimus was well tolerated and
    several secondary measures and EEG biomarkers showed signals of improvement.
  target_phenotypes:
  - preferred_term: Autism
    term:
      id: HP:0000717
      label: Autism
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: clinicaltrials:NCT02991807
    reference_title: A Randomized Double-Blind Controlled Trial of Everolimus in Individuals With PTEN Mutations (RAD001XUS257T)
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Investigators are conducting research to evaluate the potential safety and efficacy of RAD001 (everolimus) in this patient population, and the potential neurocognitive benefits from treatment with RAD001 or placebo for a six month period."
    explanation: "ClinicalTrials.gov record for the everolimus phase II RCT in PHTS — formal registry capture of the study reported as PMID:35594551 in the mTOR Inhibitor Therapy treatment entry."
references:
- reference: PMID:20301661
  title: "PTEN Hamartoma Tumor Syndrome."
  tags:
  - GeneReviews
  findings:
  - statement: GeneReviews supports Cowden syndrome/PHTS diagnostic testing, surveillance, inheritance, and family testing guidance used in this entry.
    supporting_text: PMID:20301661 for the GeneReviews clinical characteristics, diagnosis/testing, management, surveillance, and genetic counseling summary.
- reference: 'url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable'
  title: "PTEN Hamartoma Tumor Syndrome - GeneReviews® - NCBI Bookshelf"
  tags:
  - GeneReviews
  findings:
  - statement: Full GeneReviews chapter supports the pathognomonic/major/minor diagnostic criteria, PTEN testing cascade, and non-PHTS Cowden-like gene-boundary nuance.
    supporting_text: Full GeneReviews chapter for detailed Cowden syndrome clinical diagnostic criteria and molecular testing approach.

📚

References & Deep Research

References

2

PMID:20301661

PTEN Hamartoma Tumor Syndrome.

1 finding

GeneReviews supports Cowden syndrome/PHTS diagnostic testing, surveillance, inheritance, and family testing guidance used in this entry.

"PMID:20301661 for the GeneReviews clinical characteristics, diagnosis/testing, management, surveillance, and genetic counseling summary."

url:https://www.ncbi.nlm.nih.gov/books/NBK1488/?report=printable

PTEN Hamartoma Tumor Syndrome - GeneReviews® - NCBI Bookshelf

1 finding

Full GeneReviews chapter supports the pathognomonic/major/minor diagnostic criteria, PTEN testing cascade, and non-PHTS Cowden-like gene-boundary nuance.

"Full GeneReviews chapter for detailed Cowden syndrome clinical diagnostic criteria and molecular testing approach."

Deep Research

2

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (1)

Recurate Cowden Syndrome with OpenScientist deep research · 2026-08-28T11:48:42Z · View source

Recuration of an entry first curated in March 2026 without deep research. Note that unlike its sibling Gilbert's Syndrome entry, this one has been enhanced by five later sessions, so the pathophysiology, phenotype and treatment sections were already substantial. This session targeted what those sessions had not reached. Deep research: one OpenScientist report, research/Cowden_Syndrome-deep-research-openscientist.md. 30 references, all resolved, none off topic. One quoted claim was flagged as not found in source; inspection shows the flagged quote and the "closest text in source" are byte-identical, and the failure is the reference validator stripping the square-bracketed confidence interval before matching. That is a validator artifact, not a confabulation. just preflight-dr SKIPped because MONDO:0016063 records no causal RO:0004003 gene; the manual fallback passes - the report's OMIM 158350 corresponds to Cowden syndrome 1 and PTEN dominates its gene mentions at 84 against 16 for the next gene. The entry had no model systems at all, which was the largest gap. Added three, each wired into the pathograph through modeled_mechanisms rather than left as list entries: epithelial-specific Pten deletion in mouse (RECAPITULATES Hamartoma Formation at HIGH fidelity; it is the model that showed epithelial PTEN loss alone is sufficient for juvenile polyps and stromal loss is not a prerequisite), neuronal Pten deletion (RECAPITULATES Neurodevelopmental Cortical Dysfunction at MODERATE), and the PTEN-mutant iPSC forebrain organoid as an experimental_models entry. The organoid work was already cited as evidence on the neurodevelopmental node but was not modelled as a system, so the node carried its conclusion without its fidelity or limitations. Added a biochemical section, which the entry lacked entirely: elevated plasma succinate, reported in 62% of PTEN/SDHB/SDHD carriers against 16% of controls. Added the accompanying EMERGING mechanistic hypothesis that PTEN loss and SDHx variants converge on reduced succinate dehydrogenase activity, which is the only proposed account tying the entry's PTEN-positive and PTEN-negative arms together. Both are explicit that this is one small single-centre study with 21 carriers and no independent replication. Added a top-level inheritance block (autosomal dominant, INCOMPLETE penetrance, VARIABLE expressivity) and three discussions: the ERN GENTURIS guideline's own statement that surveillance effectiveness needs prospective evaluation, which matters because surveillance is this entry's strongest treatment recommendation; whether the negative everolimus trial refutes mTOR inhibition or only refutes it against a neurocognitive endpoint; and whether the reported PTEN variant-class to organ-risk correlations are replicated well enough to stratify surveillance by. Two snippets required character-level correction before they verified. One cited paper's full text uses non-breaking hyphens (U+2011) where the visible text shows ordinary hyphens; the other snippet had been truncated mid-sentence at a comma. Both were caught before commit by checking every snippet against the local cache. Validation: just validate, validate-terms, check-entity-refs, check-duplicate-keys, check-folded-hyphens, check-snippet-length, check-title-snippets and check-snippet-grading all pass. 84 of 84 snippets verify against the local reference cache. Review round 1 on the sibling PR #9830 found two structural defects that this entry had too, so they were fixed here proactively rather than waiting for the same review. First, the pten_sdhx_succinate_convergence hypothesis group was orphaned: it was declared in mechanistic_hypotheses but no causal edge opted into it, so it rendered as a disconnected assertion. Fixing it properly required a node, because the hypothesis is about a step the pathograph did not contain. Added a "Reduced Succinate Dehydrogenase Activity" node with causal_link_type UNKNOWN on the edge into it, labelled with the hypothesis group. The node is deliberately a leaf: nothing is drawn downstream of it because what accumulated succinate would then do in Cowden syndrome has not been shown. Second, no treatment carried target_mechanisms, so nothing in the treatments section joined the pathograph. Added join points for mTOR Inhibitor Therapy (INHIBITS the PI3K/AKT/mTOR node, with the edge recording what the drug does rather than that it works), Enhanced Cancer Surveillance (MODULATES Increased Cancer Risk, acting on detection timing rather than incidence) and Prophylactic Mastectomy (INHIBITS, by removing the substrate tissue). Genetic Counseling deliberately has none: it does not act on a disease mechanism. Review round 1 (ai4c-reviewer, changes requested). Four blocking items, all verified against the cached sources and all upheld. The surveillance-effectiveness discussion cited the guideline's generic disease-description opener rather than the sentence making its claim. The guideline does say it, verbatim - "There is a need for prospective evaluation of the effectiveness of these recommendations in the PHTS population" - and that sentence plus the patient-commitment sentence now carry the discussion. The organoid limitations field flattened the cited paper's headline finding. It said divergence appears only after roughly 72 days; that is the M134R cancer allele. The G132D ASD allele - the one relevant to the neurodevelopmental node - disrupts neuroectoderm formation within the first several days. Both the description and the limitations now carry the two-allele, two-timescale result. The inheritance block asserted that a substantial proportion of cases are de novo, with no citation and no source in the entry supporting it. GeneReviews, already cached here, is more cautious: the simplex/familial split cannot be determined because the condition is underdiagnosed, perhaps 10-50% have an affected parent, and simplex is not de novo. The claim was replaced with the sourced 50% transmission risk and the GeneReviews hedge, quoted at length because the hedge is the point. PMID:24469394 was fetched into the cache and then not used. The reviewer was right that this falls short of the PR's own declared scope: breast cancer is the largest risk in the entry at 77% cumulative to age 70, and neither added model touched it. Added as a third animal model - mammary Pten loss with constitutive Stat5 activation, PARTIALLY_RECAPITULATES against Increased Cancer Risk, with the interventional Stat5-ablation arm as its readout and an explicit limitation that the cooperating Stat5 lesion is engineered rather than something patients carry. Also acted on two suggestions. The organoid link-level evidence was background (an ASD prevalence statistic) rather than a statement that the model is informative for the node; it now quotes the isogenic-design sentence. And the paper's perifosine rescue arm is now a second RESCUES link with a RESTORED readout, which is the entry's only demonstration that the phenotype responds to inhibiting the pathway, in human tissue. Two suggestions were noted and not acted on. The KLLN H3K9me3 genomic-instability mechanism (PMID:26673699, the other unused cache file) is a real gap but needs a pathophysiology node, which is outside this PR's scope. And the neuronal Pten entry aggregates several models behind a review citation; its limitations field discloses this, and replacing it with a primary study is better done as its own change. The reviewer's remaining suggestion - that the succinate hypothesis group had no edge opting into it - had already been fixed in e86bfed before the review was posted, by adding the Reduced Succinate Dehydrogenase Activity node. Review round 2 raised one new item, and it was upheld. The Enhanced Cancer Surveillance treatment had been given a MODULATES edge to Increased Cancer Risk. MODULATES is defined in the schema as altering the mechanism, and the link's own description opened by saying surveillance does not change the risk - so the edge asserted the opposite of its own payload. Surveillance shifts when disease is detected, and dismech has no predicate for that; the honest encoding is no edge. Removed, with a notes line recording why, and the treatment still reaches the pathograph through the discussion that attaches to it. The reviewer named the pressure correctly: a compliance metric rewards treatments joining the pathograph, and that is why the edge was added. Correctness wins. Also grounded the succinate node's own named claim, which annotated only the metabolite: added GO:0000104 succinate dehydrogenase activity with modifier DECREASED alongside the existing CHEBI succinate annotation. They are different claims, which is the point of the node. Review round 4 approved the PR and raised five non-blocking suggestions. Four were acted on. The important one was a silent reversion this session caused. The commit that added the deep-research reference caches copied files from the primary checkout, and for PMID:26673699 that overwrote a full_text_xml cache with an abstract_only one - 95 lines of KLLN full text lost. The reviewer caught it. Regenerated with just fetch-reference, which restored the full text. An audit of all three files that commit modified rather than added found one further, smaller instance on the Gilbert's PR (PMID:28338110 lost its full_text_attempted line, no content), fixed there the same way. The lesson generalises: copying cache files between checkouts is not the sanctioned fetch path, and diffing modifications separately from additions is what surfaces it. Also moved the surveillance no-edge rationale from notes: to review_notes:, since it is a curation decision rather than disease content and notes: renders as clinical prose; changed the mammary readout direction from DECREASED to ABOLISHED, since the source says prevented rather than reduced; and gave the perifosine link its own evidence sentence (the single-cell RNAseq result showing AKT inhibition upregulates neuronal cell-fate signatures) so that the link and its readout no longer rest on the same quote, which the two-layer evidence model requires. One suggestion was noted and not acted on: GeneReviews is graded HUMAN_CLINICAL six times in this file and OTHER twice in the new inheritance block. The reviewer checked it and judged it defensible, and so do I - the two new quotes are Mendelian arithmetic and a statement about the literature rather than patient observations.

Falcon ▸

Cowden Syndrome (PTEN Hamartoma Tumor Syndrome, PHTS): Disease Characteristics Research Report

Edison Scientific Literature 46 citations 2026-04-25T17:04:44.801252

Cowden Syndrome (PTEN Hamartoma Tumor Syndrome, PHTS): Disease Characteristics Research Report

1. Disease Information

1.1 Concise overview

Cowden syndrome (CS) is a multisystem hamartoma and cancer predisposition disorder within the broader PTEN hamartoma tumor syndrome (PHTS) spectrum, characterized by mucocutaneous lesions, macrocephaly, gastrointestinal hamartomatous polyps, and elevated risks of multiple malignancies (notably breast, thyroid, endometrial, colorectal, and renal cancers). It is typically caused by heterozygous germline pathogenic variants in PTEN, resulting in dysregulated growth control via PI3K/AKT/mTOR signaling. (pirlog2024insightsintoclinical pages 1-2, takayama2023clinicalguidelinesfor pages 2-4)

1.2 Key identifiers (as available from retrieved sources)

MONDO: Cowden syndrome 1 MONDO_0008021; Cowden disease MONDO_0016063 (cummings2023cancerriskassociated pages 1-2)
OMIM: Cowden syndrome 158350 (explicitly stated in a 2023 case review) (jurca2023anewframeshift pages 9-10)
Orphanet / ICD-10 / ICD-11 / MeSH: Not found in retrieved sources in this run (insufficient evidence in retrieved texts to cite).

1.3 Synonyms and alternative names

Cowden syndrome; Cowden disease; PTEN hamartoma tumor syndrome (umbrella term) (takayama2023clinicalguidelinesfor pages 2-4, pilarski2019ptenhamartomatumor pages 1-3)
Related phenotypes within the PHTS umbrella include Bannayan–Riley–Ruvalcaba syndrome (BRRS), Proteus syndrome, Proteus-like syndrome, and adult Lhermitte–Duclos disease (pilarski2019ptenhamartomatumor pages 1-3, pirlog2024insightsintoclinical pages 1-2).

1.4 Evidence provenance (individual-level vs aggregated resources)

Much of the evidence base for CS/PHTS includes (i) aggregated guideline and cohort estimates (e.g., lifetime cancer risk ranges across cohorts, surveillance guidelines) and (ii) clinic-ascertained cohorts with ascertainment bias concerns. For example, cancer risk estimates vary substantially across studies, and reviews emphasize cautious interpretation because cohorts often include index cases and prevalent cancers. (hendricks2021areviewon pages 1-4, pilarski2019ptenhamartomatumor pages 3-5)

2. Etiology

2.1 Disease causal factors

Primary cause: heterozygous germline pathogenic variants in the tumor suppressor PTEN (autosomal dominant), leading to loss of PTEN function and downstream pathway dysregulation. (pirlog2024insightsintoclinical pages 1-2, takayama2023clinicalguidelinesfor pages 2-4)

Pathway consequence: PTEN normally dephosphorylates PIP3 to PIP2, antagonizing PI3K signaling and limiting AKT/mTOR pathway activation. PTEN loss-of-function therefore permits increased PI3K/AKT/mTOR signaling that promotes overgrowth/hamartomas and cancer predisposition. (yehia2020ptenhamartomatumour pages 5-6, pirlog2024insightsintoclinical pages 1-2)

2.2 Risk factors

Genetic: Germline PTEN pathogenic variants drive disease and confer elevated risks of multiple cancers (breast, endometrium, thyroid, colon polyposis/cancer, renal). In a large hereditary cancer panel-testing cohort (727,091 individuals tested), PTEN PV carriers had increased risk (odds ratios) for female breast cancer (OR 7.88), endometrial cancer (OR 13.51), thyroid cancer (OR 4.88), and colon polyposis (OR 31.60), with modest evidence for ovarian cancer (OR 3.77). (cummings2023cancerriskassociated pages 1-2)
Phenotype-genotype heterogeneity: Clinical CS criteria and PTEN-variant status incompletely overlap: reviews note only ~30–35% of individuals meeting clinical CS diagnostic criteria have detectable PTEN variants, underscoring heterogeneity and the role of ascertainment. (pilarski2019ptenhamartomatumor pages 1-3, cummings2023cancerriskassociated pages 1-2)

2.3 Protective factors

No specific genetic or environmental protective factors were identified in retrieved sources.

2.4 Gene–environment interactions

No explicit gene–environment interaction evidence for CS/PHTS was identified in retrieved sources.

3. Phenotypes

The phenotype spectrum is broad and age-dependent, with pediatric presentations often dominated by macrocephaly and neurodevelopmental issues, and adult presentations more often demonstrating classic mucocutaneous lesions, polyposis, and malignancies. (martinvalbuena2024ptenhamartomatumor pages 1-2)

Phenotype	HPO term suggestion	Typical age / notes	Frequency / statistics from evidence	Key citations
Macrocephaly	HP:0000256 Macrocephaly	Often earliest and most consistent pediatric finding; may be the presenting sign in infancy/childhood; adult diagnostic thresholds noted as ≥58 cm in women and ≥60 cm in men	100% (11/11) in a 2024 pediatric cohort; 85.1% at presentation and 96.3% post-diagnosis in a pediatric cohort of 81; 80–100% in mutation carriers in review data; 98% (46/47) in one pediatric study cited by review (martinvalbuena2024ptenhamartomatumor pages 1-2, baran2021theclinicalspectrum pages 3-4, pilarski2019ptenhamartomatumor pages 5-7, takayama2023clinicalguidelinesfor pages 6-8)	(martinvalbuena2024ptenhamartomatumor pages 1-2, baran2021theclinicalspectrum pages 3-4, pilarski2019ptenhamartomatumor pages 5-7, takayama2023clinicalguidelinesfor pages 6-8)
Mucocutaneous lesions (trichilemmomas, oral papillomas/fibromas, acral keratoses)	HP:0010618 Trichilemmoma; HP:0009723 Skin papilloma; HP:0100767 Oral mucosal papillomatosis; HP:0007565 Multiple lipomas	Usually accumulate with age; more prominent in adults, but can occur in childhood; characteristic facial papules and multiple trichilemmomas are considered hallmark findings	Skin/oral lesions in 30.9% at presentation and 68.2% after diagnosis in a pediatric cohort; oral fibromas reported in 14–76% and trichilemmomas in 6–25% across reviewed series; pediatric cohort described thumb hamartoma/lipoma and other cutaneous findings but fewer classic lesions than adults (baran2021theclinicalspectrum pages 3-4, pilarski2019ptenhamartomatumor pages 5-7, takayama2023clinicalguidelinesfor pages 6-8, martinvalbuena2024ptenhamartomatumor pages 2-3)	(baran2021theclinicalspectrum pages 3-4, pilarski2019ptenhamartomatumor pages 5-7, takayama2023clinicalguidelinesfor pages 6-8, martinvalbuena2024ptenhamartomatumor pages 2-3)
Gastrointestinal polyps / GI manifestations	HP:0200063 Hamartomatous polyposis; HP:0002242 Constipation; HP:0011473 Feeding difficulties	Polyps may appear in childhood but burden increases with age; adults can have few to hundreds of polyps; symptomatic children may present with constipation/feeding issues	>90% of patients undergoing upper endoscopy/colonoscopy had GI polyps in guideline review; up to 95% of adults with PTEN variants who had colonoscopy had polyps; in 80 children, GI polyps occurred in 28% (22/80), constipation in 51% (41/80), feeding issues in 39% (31/80), eosinophilic GI disorders in 6% (5/80) (takayama2023clinicalguidelinesfor pages 6-8, pilarski2019ptenhamartomatumor pages 5-7, liu2024abiinstitutionalstudy pages 1-2)	(takayama2023clinicalguidelinesfor pages 6-8, pilarski2019ptenhamartomatumor pages 5-7, liu2024abiinstitutionalstudy pages 1-2)
Thyroid nodules / thyroid abnormalities / differentiated thyroid carcinoma	HP:0000821 Goiter; HP:0002664 Thyroid carcinoma; HP:0000857 Thyroid nodule; HP:0002716 Autoimmune thyroiditis	Thyroid disease can begin in childhood; some guidelines recommend ultrasound from diagnosis because cancer has been reported as early as age 7; pediatric cancers generally low-invasive	In 43 surveilled children: thyroid abnormalities 84%, nodular disease 74%, goiter 30%, autoimmune thyroiditis 12%, nodular growth 33%, thyroidectomy 16%, DTC 5% (2/43) at ages 12 and 17; prior pediatric estimates for DTC 4–12% with median age ~12 years (range 4–17); another pediatric cohort reported thyroid cancer in 7.4% (6/81), all >10 years old (bormans2024experienceina pages 1-2, baran2021theclinicalspectrum pages 3-4, takayama2023clinicalguidelinesfor pages 6-8)	(bormans2024experienceina pages 1-2, baran2021theclinicalspectrum pages 3-4, takayama2023clinicalguidelinesfor pages 6-8)
Neurodevelopmental delay / intellectual disability / autism spectrum disorder	HP:0001263 Developmental delay; HP:0001249 Intellectual disability; HP:0000729 Autism	Often prominent in childhood and can drive referral for testing; neurobehavioral phenotype appears relatively stable over time in longitudinal study	Developmental delay in 5/11 children in one cohort; in 81 children, DD/ID present in 42.0% and ASD in 27.2%; guideline review reports ASD in ~17% of PTEN variant carriers, PTEN variants in 10–20% of ASD with macrocephaly, and intellectual disability in 12–20%; review notes PTEN mutations found in 1–27% of ASD with macrocephaly (martinvalbuena2024ptenhamartomatumor pages 1-2, baran2021theclinicalspectrum pages 3-4, takayama2023clinicalguidelinesfor pages 6-8, pilarski2019ptenhamartomatumor pages 5-7)	(martinvalbuena2024ptenhamartomatumor pages 1-2, baran2021theclinicalspectrum pages 3-4, takayama2023clinicalguidelinesfor pages 6-8, pilarski2019ptenhamartomatumor pages 5-7)
Vascular malformations / vascular anomalies	HP:0005306 Vascular malformation	May occur in childhood or adulthood; often part of BRRS/PHTS overlap and may be under-recognized	Guideline review reports multiple vascular malformations in approximately half of patients; pediatric surveillance paper lists vascular malformations among recognized manifestations but does not quantify them in that cohort (takayama2023clinicalguidelinesfor pages 6-8, bormans2024experienceina pages 1-2)	(takayama2023clinicalguidelinesfor pages 6-8, bormans2024experienceina pages 1-2)
Lhermitte–Duclos disease (dysplastic cerebellar gangliocytoma)	HP:0006887 Dysplastic cerebellar gangliocytoma	Classically associated with adult disease, often diagnosed in 20s–30s, but cerebellar dysplasia/LDD-compatible imaging can be seen earlier	~6% prevalence in guideline review; overlap of LDD patients with Cowden syndrome reported at ~50%; one pediatric cohort had a patient with cortical cerebellar dysplasia compatible with LDD (takayama2023clinicalguidelinesfor pages 6-8, martinvalbuena2024ptenhamartomatumor pages 6-7, pilarski2019ptenhamartomatumor pages 3-5)	(takayama2023clinicalguidelinesfor pages 6-8, martinvalbuena2024ptenhamartomatumor pages 6-7, pilarski2019ptenhamartomatumor pages 3-5)

Table: This table summarizes major clinical phenotypes reported for Cowden syndrome/PTEN hamartoma tumor syndrome, with suggested HPO terms, timing, and quantitative frequencies from recent and key studies. It is useful for phenotype curation and knowledge base population.

Quality-of-life impact (selected)

Direct quality-of-life (EQ-5D/SF-36/PROMIS) statistics were not identified in retrieved sources. However, multiple phenotypes have substantial functional impacts: neurodevelopmental disorders (developmental delay, ASD), obstructive sleep apnea related to tonsillar pathology, and repeated cancer surveillance/surgery burden. (baran2021theclinicalspectrum pages 3-4, bormans2024experienceina pages 1-2)

4. Genetic / Molecular Information

4.1 Causal gene(s)

PTEN is the primary causal gene for Cowden syndrome/PHTS in the retrieved sources. (pirlog2024insightsintoclinical pages 1-2, takayama2023clinicalguidelinesfor pages 2-4)

4.2 Pathogenic variant classes and consequences (high-level)

PTEN pathogenic variants may be truncating (nonsense/frameshift), missense, splice-site, or structural; functionally, many act via loss of function leading to elevated PI3K pathway signaling and impaired genome-stability functions. (yehia2020ptenhamartomatumour pages 5-6, wei2024quantitativeevaluationof pages 1-2)
In patient-derived lymphoblastoid cell lines, PTEN nonsense variants were associated with less efficient DNA damage repair dynamics (higher residual damage at 24 hours after irradiation) compared with missense variants, supporting a genotype-linked difference in genome integrity phenotypes. (wei2024quantitativeevaluationof pages 1-2)

4.3 Non-PTEN genetic etiologies / phenocopies

When a patient has a PHTS/CS-like phenotype but lacks a germline PTEN variant, germline activating variants in PI3K-pathway genes (e.g., AKT1, PIK3CA) can phenocopy PTEN loss, with increased AKT phosphorylation and increased PIP3 levels observed in patient-derived cells—“mimicking effects of PTEN loss-of-function.” (yehia2020ptenhamartomatumour pages 8-9)

4.4 Modifier genes / genomic background

No definitive modifier genes were established from retrieved sources in this run (beyond pathway-related phenocopies above).

4.5 Epigenetic information

No epigenetic mechanisms (e.g., methylation signatures) were identified in retrieved sources.

4.6 Chromosomal abnormalities

No recurrent chromosomal abnormalities were identified in retrieved sources.

5. Environmental Information

5.1 Environmental and lifestyle factors

Direct environmental risk factors for CS/PHTS were not identified in retrieved sources. The disease is primarily genetic.

6. Mechanism / Pathophysiology

6.1 Core molecular pathway mechanism (upstream → downstream)

1) Trigger: germline PTEN loss-of-function (heterozygous) (pirlog2024insightsintoclinical pages 1-2) 2) Molecular effect: reduced dephosphorylation of PIP3 → increased PIP3 and increased AKT activation → increased downstream growth signaling including mTOR activity (yehia2020ptenhamartomatumour pages 5-6, pirlog2024insightsintoclinical pages 1-2) 3) Cellular consequences: increased proliferation/survival and disordered growth leading to hamartomas/overgrowth; tumor predisposition due to growth signaling plus PTEN roles in nuclear genome stability and DNA double-strand break repair (yehia2020ptenhamartomatumour pages 5-6) 4) Clinical outcomes: multisystem hamartomas (skin/oral mucosa, GI tract, thyroid, breast, etc.) and increased cancer risks with earlier onset (pirlog2024insightsintoclinical pages 1-2, cummings2023cancerriskassociated pages 1-2)

6.2 Genome integrity / DNA damage response as a contributor to pleiotropy

PTEN has non-canonical roles relevant to “maintenance of genome integrity,” and quantitative DNA damage response modeling in PTEN-variant patient cell lines showed variant-class and phenotype associations (e.g., less efficient repair in nonsense variants; different repair dynamics in ASD/DD vs cancer phenotypic subgroups), providing a mechanistic framework for pleiotropic outcomes. (wei2024quantitativeevaluationof pages 1-2)

6.3 Immune dysregulation (emerging/variable evidence)

Immune dysregulation is increasingly reported in PHTS. A 2024 case report links PTEN mutation and immune dysregulation in the context of systemic lupus erythematosus (SLE), emphasizing PTEN’s regulation of PI3K/AKT/mTOR signaling relevant to immune function. (drozdz2024severelupusnephritis pages 1-2)

Suggested ontology terms

GO Biological Process (examples): PI3K signaling (e.g., “phosphatidylinositol 3-kinase signaling”); regulation of cell proliferation; DNA repair / double-strand break repair; regulation of apoptosis (mechanistically supported by PTEN roles described in retrieved sources) (yehia2020ptenhamartomatumour pages 5-6, wei2024quantitativeevaluationof pages 1-2)
Cell types (CL suggestions, examples): epithelial cells (breast/thyroid/endometrium), colonic epithelial cells; endothelial cells (vascular malformations noted clinically); lymphocytes (immune dysregulation discussions) (takayama2023clinicalguidelinesfor pages 6-8, drozdz2024severelupusnephritis pages 1-2)

7. Anatomical Structures Affected

7.1 Organ-level involvement (primary)

Commonly involved organs/systems include: - Skin and mucous membranes (mucocutaneous lesions) (takayama2023clinicalguidelinesfor pages 2-4, pilarski2019ptenhamartomatumor pages 5-7) - Gastrointestinal tract (hamartomatous polyps; constipation/feeding issues in children) (takayama2023clinicalguidelinesfor pages 6-8, liu2024abiinstitutionalstudy pages 1-2) - Thyroid (nodules, goiter, autoimmune thyroiditis, differentiated thyroid carcinoma) (bormans2024experienceina pages 1-2) - Breast, endometrium, kidney, colon (cancer predisposition) (cummings2023cancerriskassociated pages 1-2, hendricks2021areviewon pages 1-4) - Central nervous system (macrocephaly; MRI abnormalities; Lhermitte–Duclos disease) (pilarski2019ptenhamartomatumor pages 5-7, takayama2023clinicalguidelinesfor pages 6-8)

7.2 Tissue/cell-level and subcellular notes

At a mechanistic level, PTEN functions at the plasma membrane (PIP3→PIP2 dephosphorylation) and in the nucleus (genomic stability/cell cycle regulation), providing plausible cross-tissue impact on growth and tumor suppression. (yehia2020ptenhamartomatumour pages 5-6)

7.3 UBERON term suggestions (examples)

Thyroid gland; breast; endometrium; colon; kidney; cerebellum; skin; oral mucosa; gastrointestinal tract (supported by multisystem involvement described in guidelines/reviews) (takayama2023clinicalguidelinesfor pages 2-4, takayama2023clinicalguidelinesfor pages 6-8)

8. Temporal Development

8.1 Onset and progression

Many individuals demonstrate early manifestations such as macrocephaly and neurodevelopmental concerns in childhood, whereas mucocutaneous lesions and some cancer manifestations often become more apparent in adolescence/adulthood. (martinvalbuena2024ptenhamartomatumor pages 1-2, baran2021theclinicalspectrum pages 3-4)
Median age at cancer diagnosis has been reported around 36 years in CS/PHTS cohorts summarized in reviews. (pirlog2024insightsintoclinical pages 1-2, hendricks2021areviewon pages 1-4)

9. Inheritance and Population

9.1 Inheritance

CS/PHTS is autosomal dominant due to heterozygous germline PTEN pathogenic variants. (pirlog2024insightsintoclinical pages 1-2, takayama2023clinicalguidelinesfor pages 2-4)

9.2 Penetrance and expressivity

CS/PHTS shows high penetrance with variable expressivity; one pediatric cohort report cites penetrance approaching ~100% by the fourth decade for pathogenic PTEN variants and reports de novo rates from ~10.7% to 47.6% (range across literature). (martinvalbuena2024ptenhamartomatumor pages 1-2)

9.3 Epidemiology

A commonly cited prevalence/incidence estimate for Cowden syndrome/PHTS in reviews is approximately 1 in 200,000, while multiple sources emphasize that true incidence is uncertain and likely under-recognized. (pirlog2024insightsintoclinical pages 1-2, hendricks2021areviewon pages 1-4)

9.4 Recent population-level genetic testing statistic

In a large hereditary cancer panel-testing cohort (testing 2013–2022), PTEN pathogenic variants were detected in 0.027% (193/727,091) of tested individuals. (cummings2023cancerriskassociated pages 1-2)

10. Diagnostics

10.1 Clinical criteria and diagnostic framework

Contemporary clinical diagnosis commonly uses frameworks aligned with NCCN criteria for CS/PHTS; the Japanese 2023 guideline explicitly adopted an NCCN-based framework (noting 8 major and 10 minor criteria) and provides a diagnostic flowchart. (takayama2023clinicalguidelinesfor pages 2-4)
Because clinical criteria and PTEN variant detection incompletely overlap (only a subset meeting CS criteria have PTEN variants), diagnosis may be made clinically even if genetic testing is negative/unavailable, but this complicates gene-informed risk assessment. (pilarski2019ptenhamartomatumor pages 1-3, yehia2020ptenhamartomatumour pages 8-9)

10.2 Genetic testing approach (current understanding)

Multigene cancer predisposition panels and targeted PTEN testing are used in clinical practice and can identify PTEN PVs even in individuals not previously recognized clinically as having CS. The panel-testing cohort study emphasizes that risk estimates derived purely from clinically diagnosed CS cohorts may be biased, motivating genotype-based risk modeling. (cummings2023cancerriskassociated pages 1-2)

10.3 Differential diagnosis (selected)

PTEN-wildtype CS-like phenotypes may be due to variants in PI3K-pathway genes (e.g., AKT1, PIK3CA), which can mimic PTEN loss, reinforcing the need for differential genetic evaluation in PTEN-negative cases. (yehia2020ptenhamartomatumour pages 8-9)

11. Outcome / Prognosis

11.1 Cancer risk burden (statistics from cohorts)

Aggregated cohort data summarized in a 2021 review report cumulative lifetime risk for any cancer of 81%–90% in PHTS, with wide ranges by cancer site (female breast 67%–85% by age 60–70; endometrium 19%–28%; thyroid 6%–38%; renal 2%–24%; colorectal 9%–32%; melanoma 0%–6%). (hendricks2021areviewon pages 1-4)

11.2 Surveillance yield (real-world implementation data)

In a PHTS expertise center cohort (children screened by thyroid ultrasound before 18 years), 2/43 (5%) had differentiated thyroid carcinoma (ages 12 and 17), and 84% had thyroid abnormalities (mostly benign), illustrating high surveillance burden and nontrivial detection yield. (bormans2024experienceina pages 1-2)

12. Treatment

12.1 Standard treatments

Cancers in CS/PHTS are generally treated according to standard organ-specific oncology/surgical care pathways; no PHTS-specific renal cancer treatment evidence was found in the retrieved guideline excerpt, which notes following sporadic RCC management. (takayama2023clinicalguidelinesfor pages 8-11)

12.2 Targeted/experimental therapeutics (mechanism-informed)

Guidelines and reviews note that PI3K/AKT/mTOR pathway inhibitors are being investigated clinically because PTEN inactivation converges on this pathway. (takayama2023clinicalguidelinesfor pages 8-11)

MAXO term suggestions (examples): cancer surveillance; breast MRI screening; thyroid ultrasound screening; colonoscopy; nephrologic imaging surveillance; prophylactic mastectomy (consideration) (tischkowitz2020cancersurveillanceguideline pages 2-4, takayama2023clinicalguidelinesfor pages 8-11)

13. Prevention

Because CS/PHTS is Mendelian, prevention focuses on secondary prevention (early cancer detection via surveillance) rather than primary prevention.

13.1 Surveillance (secondary prevention): key guideline recommendations

The ERN GENTURIS guideline provides organ-specific surveillance with evidence-strength grading.

Key schedule elements (also shown in the guideline’s table image): - Breast: annual MRI from age 30; mammography every 2 years from age 40 (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline media 2ffc24d6) - Thyroid: annual ultrasound from ~age 18 (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline media 2ffc24d6) - Renal: ultrasound every 2 years from age ~40 (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline media 2ffc24d6) - Colon: baseline colonoscopy at 35–40 to assess polyp load (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline media 2ffc24d6) - Endometrium: routine screening not recommended; consider within trials (tischkowitz2020cancersurveillanceguideline pages 2-4)

The Japanese guideline (NCCN-aligned) recommends earlier surveillance for some sites: - Breast: self-exam from 18; clinical exams from 25; annual mammography + contrast MRI from 30 (or 5–10 years earlier than the youngest family diagnosis) (takayama2023clinicalguidelinesfor pages 8-11) - Thyroid: annual ultrasound from diagnosis, including in children, motivated by pediatric thyroid cancer reports (earliest age 7; ~5% risk <20 years cited) (takayama2023clinicalguidelinesfor pages 11-12, takayama2023clinicalguidelinesfor pages 8-11)

Cancer site	Reported risk estimates	ERN GENTURIS / European guideline start age & modality	NCCN / Japanese guideline start age & modality	Evidence strength (if stated)	Notes / controversies
Breast	Female breast cancer CLTR 67%–85% by age 60–70 in prior cohorts; PTEN PVs associated with OR 7.88 (95% CI 5.57–11.16) in a panel-testing cohort (hendricks2021areviewon pages 1-4, cummings2023cancerriskassociated pages 1-2)	Annual breast MRI from age 30; mammography every 2 years from age 40; risk-reducing surgery may be offered (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5, tischkowitz2020cancersurveillanceguideline media 2ffc24d6)	Monthly self-exam from 18; clinical breast exam/interview from 25 or 5–10 years before youngest family cancer; annual mammography plus gadolinium-enhanced breast MRI from 30 or 5–10 years before youngest familial onset (takayama2023clinicalguidelinesfor pages 8-11)	MRI: Strong; mammography/risk-reducing surgery: Moderate (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5)	Lifetime risk estimates vary widely across cohorts because of ascertainment bias; Takayama notes no evidence that prophylactic mastectomy improves overall survival (hendricks2021areviewon pages 1-4, takayama2023clinicalguidelinesfor pages 8-11)
Thyroid	Thyroid cancer CLTR 6%–38% in review cohorts; historical/literature estimates often 10%–35%; PTEN PVs associated with OR 4.88 (95% CI 2.64–9.01); pediatric DTC estimates 4%–12%; in one pediatric surveillance cohort, 2/43 (5%) had DTC and 84% had thyroid abnormalities (hendricks2021areviewon pages 1-4, pilarski2019ptenhamartomatumor pages 3-5, cummings2023cancerriskassociated pages 1-2, bormans2024experienceina pages 1-2)	Annual thyroid ultrasound from about age 18 (table lists 18a) (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5, tischkowitz2020cancersurveillanceguideline media 2ffc24d6)	Annual thyroid ultrasonography at diagnosis, including childhood; rationale includes thyroid cancer reported at age 7 and ~5% risk in patients <20 years (takayama2023clinicalguidelinesfor pages 11-12, takayama2023clinicalguidelinesfor pages 8-11)	Strong (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5)	Major divergence between guidelines: ERN starts around 18, while NCCN/Japanese guidance starts in childhood/at diagnosis; pediatric series support earlier surveillance in expertise centers, sometimes from age 12 (pirlog2024insightsintoclinical pages 11-12, takayama2023clinicalguidelinesfor pages 11-12, bormans2024experienceina pages 1-2)
Endometrial	Endometrial cancer CLTR 19%–28%; PTEN PVs associated with OR 13.51 (95% CI 8.77–20.83) (hendricks2021areviewon pages 1-4, pilarski2019ptenhamartomatumor pages 3-5, cummings2023cancerriskassociated pages 1-2)	Routine screening not recommended; if surveillance is offered, guideline suggests this should preferably be in clinical trials, and if offered probably at least annually (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5)	Yearly transvaginal ultrasound or endometrial biopsy beginning at age 30 (Japanese guideline) (takayama2023clinicalguidelinesfor pages 11-12)	Weak (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5)	Substantial controversy: ERN does not recommend routine endometrial surveillance outside trials, whereas Japanese/NCCN-derived guidance is more proactive; evidence base remains limited (pirlog2024insightsintoclinical pages 11-12, takayama2023clinicalguidelinesfor pages 11-12)
Colorectal	Colorectal cancer CLTR 9%–32% in review cohorts; prevalence in cohorts often 9%–13%; one estimate 9% lifetime and another 16%; PTEN PVs strongly associated with colon polyposis OR 31.60 (95% CI 15.60–64.02) (hendricks2021areviewon pages 1-4, pilarski2019ptenhamartomatumor pages 3-5, cummings2023cancerriskassociated pages 1-2)	Baseline colonoscopy at age 35–40 to assess polyp load; if normal, follow general-population screening, with further surveillance as required (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5, tischkowitz2020cancersurveillanceguideline media 2ffc24d6)	Total colonoscopy 5–10 years before age 35 or before youngest family cancer onset; interval depends on degree of polyposis; adenomatous polyps ≥6 mm should be resected (takayama2023clinicalguidelinesfor pages 11-12)	Moderate for baseline colonoscopy (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5)	Risk may be lower than historically estimated; a surveillance cohort found no CRCs over 67 follow-up years, supporting personalized intervals rather than uniformly intensive screening (tischkowitz2020cancersurveillanceguideline pages 1-2, takayama2023clinicalguidelinesfor pages 11-12)
Renal	Renal cancer CLTR 2%–24% in review cohorts; some small studies projected up to ~34% lifetime risk, likely overestimated (hendricks2021areviewon pages 1-4, pilarski2019ptenhamartomatumor pages 3-5)	Renal ultrasound every 2 years starting about age 40 (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5, tischkowitz2020cancersurveillanceguideline media 2ffc24d6)	Annual renal ultrasonography from age 40; some sources mention CT or preferably MRI if needed (takayama2023clinicalguidelinesfor pages 11-12, jurca2023anewframeshift pages 9-10)	Moderate (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5)	ERN notes insufficient data to recommend renal MRI routinely; early-onset RCC case reports have prompted debate about lowering surveillance age, but this is not standardized (tischkowitz2020cancersurveillanceguideline pages 4-5, jurca2023anewframeshift pages 9-10)
Melanoma / skin	Melanoma CLTR 0%–6%; evidence for increased melanoma risk remains limited, with some cohorts showing ~1% prevalence and others projecting 6% lifetime (hendricks2021areviewon pages 1-4, pilarski2019ptenhamartomatumor pages 3-5)	Baseline skin examination around age 30; no strong recommendation for additional routine surveillance beyond this (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5, tischkowitz2020cancersurveillanceguideline media 2ffc24d6)	No explicit melanoma screening schedule retrieved in Takayama 2023; strong recommendation for dermatology referral to assess mucocutaneous lesions (takayama2023clinicalguidelinesfor pages 11-12)	Weak (tischkowitz2020cancersurveillanceguideline pages 2-4, tischkowitz2020cancersurveillanceguideline pages 4-5)	Skin surveillance is limited by uncertain melanoma risk, but dermatologic evaluation remains clinically valuable because mucocutaneous lesions are prominent and may support diagnosis (tischkowitz2020cancersurveillanceguideline pages 4-5, takayama2023clinicalguidelinesfor pages 11-12)

Table: This table summarizes site-specific cancer risk estimates and surveillance recommendations for Cowden syndrome/PTEN hamartoma tumor syndrome. It contrasts ERN GENTURIS and NCCN/Japanese approaches and highlights where evidence is strong versus where recommendations remain controversial.

14. Other Species / Natural Disease

No naturally occurring CS/PHTS analogs in non-human species were identified in retrieved sources in this run.

15. Model Organisms

Model organism evidence was not deeply extracted in this run; however, multiple reviews highlight that PTEN function and tumor suppression mechanisms are conserved across species and have been studied in zebrafish and Drosophila models (e.g., for tumorigenesis and variant functional assays), supporting mechanistic inference for PTEN loss. (yehia2020ptenhamartomatumour pages 5-6)

Recent developments and latest research (prioritizing 2023–2024)

2023–2024 high-value sources retrieved in this run

Japanese clinical guideline (2023-10-XX) providing English secondary publication and emphasizing NCCN-aligned diagnosis/management and the need for surveillance across breast/thyroid/endometrium/colon/kidney (Takayama et al., 2023; URL: https://doi.org/10.23922/jarc.2023-028). (takayama2023clinicalguidelinesfor pages 2-4, takayama2023clinicalguidelinesfor pages 8-11)
Large-scale panel-testing risk quantification (2023-01-XX) providing genotype-based ORs for major cancers and colon polyposis (Cummings et al., 2023; URL: https://doi.org/10.1200/po.22.00415). (cummings2023cancerriskassociated pages 1-2)
Pediatric GI/hepatic bi-institutional cohort (2024-01-XX) quantifying constipation, feeding issues, and pediatric polyp frequency in 80 children (Liu et al., 2024; URL: https://doi.org/10.1016/j.gastha.2023.10.012). (liu2024abiinstitutionalstudy pages 1-2)
Pediatric thyroid surveillance implementation study (2024-08-XX) describing high detection of benign thyroid abnormalities and DTC yield (Bormans et al., 2024; URL: https://doi.org/10.4274/jcrpe.galenos.2024.2024-3-14). (bormans2024experienceina pages 1-2)
Mechanistic DDR phenotyping + modeling (2024-10-XX) linking PTEN variant class to DNA repair dynamics and exploring phenotype prediction (Wei et al., 2024; URL: https://doi.org/10.1371/journal.pcbi.1012449). (wei2024quantitativeevaluationof pages 1-2)
Comprehensive CS clinical review (2024-05-XX) summarizing multisystem manifestations and describing inter-guideline differences (Pîrlog et al., 2024; URL: https://doi.org/10.3390/medicina60050767). (pirlog2024insightsintoclinical pages 2-4, pirlog2024insightsintoclinical pages 11-12)

Embedded summary artifacts

Concept	MONDO ID	OMIM	Key synonyms/related syndromes	Causal gene	Inheritance	Notes on ascertainment
Cowden syndrome	MONDO_0008021 (Cowden syndrome 1); MONDO_0016063 (Cowden disease)	158350	Cowden disease; Cowden syndrome (CS); related PTEN-spectrum entities include Bannayan–Riley–Ruvalcaba syndrome (BRRS), Proteus syndrome, Proteus-like syndrome, adult Lhermitte–Duclos disease	PTEN	Autosomal dominant	Clinical and molecular diagnosis do not fully overlap: only ~30–35% of individuals meeting clinical CS criteria have a detectable PTEN variant in cited reviews; diagnosis may be made clinically and/or by multigene panel testing (pilarski2019ptenhamartomatumor pages 1-3, pirlog2024insightsintoclinical pages 1-2, takayama2023clinicalguidelinesfor pages 2-4)
PTEN hamartoma tumor syndrome (PHTS) umbrella	Not found in retrieved sources	Not found in retrieved sources	PTEN hamartoma tumour/tumor syndrome; umbrella including Cowden syndrome, BRRS, Proteus syndrome, Proteus-like syndrome, and adult Lhermitte–Duclos disease; autism spectrum disorder with macrocephaly is also described within the PTEN-related spectrum	PTEN	Autosomal dominant	PHTS is an umbrella term for PTEN-related disorders; PTEN pathogenic variants were found in only a subset of clinically diagnosed phenotypes (e.g., ~30–35% of CS/CS-like and ~60% of BRRS in cited reviews), underscoring phenotype–genotype heterogeneity and ascertainment differences between clinically defined and genetically confirmed cohorts (cummings2023cancerriskassociated pages 1-2, pilarski2019ptenhamartomatumor pages 1-3, pirlog2024insightsintoclinical pages 1-2)

Table: This table summarizes the key identifiers, synonyms, causal gene, and inheritance for Cowden syndrome and the broader PTEN hamartoma tumor syndrome umbrella. It also highlights the important distinction between clinical diagnosis and genetically confirmed PTEN-associated disease.

Key guideline table image (visual evidence)

The extracted table image from the ERN GENTURIS surveillance guideline (European Journal of Human Genetics, 2020) summarizes screening start ages and modalities across organ sites. (tischkowitz2020cancersurveillanceguideline media 2ffc24d6)

Notes on evidence gaps (from retrieved sources in this run)

ICD-10/ICD-11, Orphanet, MeSH identifiers were not present in retrieved sources in this run; inclusion would require targeted retrieval from OMIM/Orphanet/WHO/NCBI MeSH.
Quality-of-life instruments, formal epidemiologic incidence, and long-term survival statistics were not directly retrieved.
Animal model and comparative disease sections were not fully supported by extracted evidence in this run; additional targeted model-organism papers could strengthen this component.

References

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(martinvalbuena2024ptenhamartomatumor pages 2-3): Jesús Martín-Valbuena, Nerea Gestoso-Uzal, María Justel-Rodríguez, María Isidoro-García, Elena Marcos-Vadillo, Sandra Milagros Lorenzo-Hernández, M. Carla Criado-Muriel, and Pablo Prieto-Matos. Pten hamartoma tumor syndrome: clinical and genetic characterization in pediatric patients. Child's Nervous System, 40:1689-1697, Feb 2024. URL: https://doi.org/10.1007/s00381-024-06301-2, doi:10.1007/s00381-024-06301-2. This article has 9 citations.
(liu2024abiinstitutionalstudy pages 1-2): Darren Liu, Suzanne P. MacFarland, Lamis Yehia, Melani M. Duvall, Petar Mamula, Jacob A. Kurowski, Colleen S. Greene, Kadakkal Radhakrishnan, and Charis Eng. A bi-institutional study of gastrointestinal and hepatic manifestations in children with pten hamartoma tumor syndrome. Gastro Hep Advances, 3:250-259, Jan 2024. URL: https://doi.org/10.1016/j.gastha.2023.10.012, doi:10.1016/j.gastha.2023.10.012. This article has 4 citations and is from a peer-reviewed journal.
(bormans2024experienceina pages 1-2): Esther M.G. Bormans, Janneke H.M. Schuurs-Hoeijmakers, Petra van Setten, Linda A.J. Hendricks, Meggie M.C.M. Drissen, Martin Gotthardt, Hedi L. Claahsen-van der Grinten, Nicoline Hoogerbrugge, and Jolanda H. Schieving. Experience in a pten hamartoma tumor syndrome expertise centre: yield of thyroid ultrasound surveillance in children with pten hamartoma tumor syndrome. Journal of Clinical Research in Pediatric Endocrinology, 17:46-57, Aug 2024. URL: https://doi.org/10.4274/jcrpe.galenos.2024.2024-3-14, doi:10.4274/jcrpe.galenos.2024.2024-3-14. This article has 2 citations.
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(yehia2020ptenhamartomatumour pages 8-9): Lamis Yehia and Charis Eng. Pten hamartoma tumour syndrome: what happens when there is no pten germline mutation? Human molecular genetics, 29:R150-R157, Jun 2020. URL: https://doi.org/10.1093/hmg/ddaa127, doi:10.1093/hmg/ddaa127. This article has 23 citations and is from a domain leading peer-reviewed journal.
(drozdz2024severelupusnephritis pages 1-2): Wiktoria Drozdz, Daniel Joller, Philipp Grosse, and Thomas Fehr. Severe lupus nephritis in a young adult with pten hamartoma tumour syndrome. BMJ Case Reports, 17:e258400, Sep 2024. URL: https://doi.org/10.1136/bcr-2023-258400, doi:10.1136/bcr-2023-258400. This article has 2 citations and is from a peer-reviewed journal.
(takayama2023clinicalguidelinesfor pages 8-11): Tetsuji Takayama, Naoki Muguruma, Masahiro Igarashi, Shozo Ohsumi, Shiro Oka, Fumihiko Kakuta, Yoshiaki Kubo, Hideki Kumagai, Mika Sasaki, Tamotsu Sugai, Kokichi Sugano, Yuko Takeda, Hisashi Doyama, Kouji Banno, Suguru Fukahori, Yoichi Furukawa, Takahiro Horimatsu, Hideki Ishikawa, Takeo Iwama, Yasushi Okazaki, Yutaka Saito, Nariaki Matsuura, Michihiro Mutoh, Naohiro Tomita, Takashi Akiyama, Toshiki Yamamoto, Hideyuki Ishida, and Yoshiko Nakayama. Clinical guidelines for diagnosis and management of cowden syndrome/pten hamartoma tumor syndrome in children and adults―secondary publication. Journal of the Anus, Rectum and Colon, 7:284-300, Oct 2023. URL: https://doi.org/10.23922/jarc.2023-028, doi:10.23922/jarc.2023-028. This article has 43 citations.
(tischkowitz2020cancersurveillanceguideline pages 2-4): M. Tischkowitz, C. Colas, Sjaak Pouwels, N. Hoogerbrugge, Tanya Virginie Frederic Nathalie Chrystelle Sophie Marti Bisseling Bubien Caux Chabbert-Buffet Colas Da Mot, T. Bisseling, V. Bubien, F. Caux, N. Chabbert-Buffet, Sophie Da Mota Gomes, M. Gotthardt, M. Kets, K. Lachlan, T. Links, M. Longy, R. Mann, L. S. Kool, R. Semple, Ian Stock, M. Tischkowitz, J. Vos, Nicoline Marjolijn Rianne Rolf Gareth Emma Marc Eamonn Rosa Hoogerbrugge Ligtenberg Oostenbrink Sijmons Evans, M. Ligtenberg, R. Oostenbrink, R. Sijmons, G. Evans, E. Woodward, E. Maher, R. Ferner, S. Aretz, I. Spier, V. Steinke-Lange, E. Holinski-Feder, E. Schröck, T. Frebourg, C. Houdayer, P. Wolkenstein, V. Bours, E. Legius, B. Poppe, K. Claes, Robin de Putter, I. Guillermo, G. Capellá, J. B. Vidal, C. Lázaro, J. Balmaña, Héctor Salvador Hernández, Carla Oliveira, M. Teixeira, S. Bajalica-Lagercrantz, E. Tham, J. Lubiński, K. Ertmańska, B. Melegh, M. Krajc, A. Blatnik, S. Peltonen, and M. Hietala. Cancer surveillance guideline for individuals with pten hamartoma tumour syndrome. European Journal of Human Genetics, 28:1387-1393, Jun 2020. URL: https://doi.org/10.1038/s41431-020-0651-7, doi:10.1038/s41431-020-0651-7. This article has 146 citations and is from a domain leading peer-reviewed journal.
(tischkowitz2020cancersurveillanceguideline media 2ffc24d6): M. Tischkowitz, C. Colas, Sjaak Pouwels, N. Hoogerbrugge, Tanya Virginie Frederic Nathalie Chrystelle Sophie Marti Bisseling Bubien Caux Chabbert-Buffet Colas Da Mot, T. Bisseling, V. Bubien, F. Caux, N. Chabbert-Buffet, Sophie Da Mota Gomes, M. Gotthardt, M. Kets, K. Lachlan, T. Links, M. Longy, R. Mann, L. S. Kool, R. Semple, Ian Stock, M. Tischkowitz, J. Vos, Nicoline Marjolijn Rianne Rolf Gareth Emma Marc Eamonn Rosa Hoogerbrugge Ligtenberg Oostenbrink Sijmons Evans, M. Ligtenberg, R. Oostenbrink, R. Sijmons, G. Evans, E. Woodward, E. Maher, R. Ferner, S. Aretz, I. Spier, V. Steinke-Lange, E. Holinski-Feder, E. Schröck, T. Frebourg, C. Houdayer, P. Wolkenstein, V. Bours, E. Legius, B. Poppe, K. Claes, Robin de Putter, I. Guillermo, G. Capellá, J. B. Vidal, C. Lázaro, J. Balmaña, Héctor Salvador Hernández, Carla Oliveira, M. Teixeira, S. Bajalica-Lagercrantz, E. Tham, J. Lubiński, K. Ertmańska, B. Melegh, M. Krajc, A. Blatnik, S. Peltonen, and M. Hietala. Cancer surveillance guideline for individuals with pten hamartoma tumour syndrome. European Journal of Human Genetics, 28:1387-1393, Jun 2020. URL: https://doi.org/10.1038/s41431-020-0651-7, doi:10.1038/s41431-020-0651-7. This article has 146 citations and is from a domain leading peer-reviewed journal.
(takayama2023clinicalguidelinesfor pages 11-12): Tetsuji Takayama, Naoki Muguruma, Masahiro Igarashi, Shozo Ohsumi, Shiro Oka, Fumihiko Kakuta, Yoshiaki Kubo, Hideki Kumagai, Mika Sasaki, Tamotsu Sugai, Kokichi Sugano, Yuko Takeda, Hisashi Doyama, Kouji Banno, Suguru Fukahori, Yoichi Furukawa, Takahiro Horimatsu, Hideki Ishikawa, Takeo Iwama, Yasushi Okazaki, Yutaka Saito, Nariaki Matsuura, Michihiro Mutoh, Naohiro Tomita, Takashi Akiyama, Toshiki Yamamoto, Hideyuki Ishida, and Yoshiko Nakayama. Clinical guidelines for diagnosis and management of cowden syndrome/pten hamartoma tumor syndrome in children and adults―secondary publication. Journal of the Anus, Rectum and Colon, 7:284-300, Oct 2023. URL: https://doi.org/10.23922/jarc.2023-028, doi:10.23922/jarc.2023-028. This article has 43 citations.
(tischkowitz2020cancersurveillanceguideline pages 4-5): M. Tischkowitz, C. Colas, Sjaak Pouwels, N. Hoogerbrugge, Tanya Virginie Frederic Nathalie Chrystelle Sophie Marti Bisseling Bubien Caux Chabbert-Buffet Colas Da Mot, T. Bisseling, V. Bubien, F. Caux, N. Chabbert-Buffet, Sophie Da Mota Gomes, M. Gotthardt, M. Kets, K. Lachlan, T. Links, M. Longy, R. Mann, L. S. Kool, R. Semple, Ian Stock, M. Tischkowitz, J. Vos, Nicoline Marjolijn Rianne Rolf Gareth Emma Marc Eamonn Rosa Hoogerbrugge Ligtenberg Oostenbrink Sijmons Evans, M. Ligtenberg, R. Oostenbrink, R. Sijmons, G. Evans, E. Woodward, E. Maher, R. Ferner, S. Aretz, I. Spier, V. Steinke-Lange, E. Holinski-Feder, E. Schröck, T. Frebourg, C. Houdayer, P. Wolkenstein, V. Bours, E. Legius, B. Poppe, K. Claes, Robin de Putter, I. Guillermo, G. Capellá, J. B. Vidal, C. Lázaro, J. Balmaña, Héctor Salvador Hernández, Carla Oliveira, M. Teixeira, S. Bajalica-Lagercrantz, E. Tham, J. Lubiński, K. Ertmańska, B. Melegh, M. Krajc, A. Blatnik, S. Peltonen, and M. Hietala. Cancer surveillance guideline for individuals with pten hamartoma tumour syndrome. European Journal of Human Genetics, 28:1387-1393, Jun 2020. URL: https://doi.org/10.1038/s41431-020-0651-7, doi:10.1038/s41431-020-0651-7. This article has 146 citations and is from a domain leading peer-reviewed journal.
(pirlog2024insightsintoclinical pages 11-12): Lorin-Manuel Pîrlog, Andrada-Adelaida Pătrășcanu, Mariela Sanda Militaru, and Andreea Cătană. Insights into clinical disorders in cowden syndrome: a comprehensive review. Medicina, 60:767, May 2024. URL: https://doi.org/10.3390/medicina60050767, doi:10.3390/medicina60050767. This article has 10 citations.
(tischkowitz2020cancersurveillanceguideline pages 1-2): M. Tischkowitz, C. Colas, Sjaak Pouwels, N. Hoogerbrugge, Tanya Virginie Frederic Nathalie Chrystelle Sophie Marti Bisseling Bubien Caux Chabbert-Buffet Colas Da Mot, T. Bisseling, V. Bubien, F. Caux, N. Chabbert-Buffet, Sophie Da Mota Gomes, M. Gotthardt, M. Kets, K. Lachlan, T. Links, M. Longy, R. Mann, L. S. Kool, R. Semple, Ian Stock, M. Tischkowitz, J. Vos, Nicoline Marjolijn Rianne Rolf Gareth Emma Marc Eamonn Rosa Hoogerbrugge Ligtenberg Oostenbrink Sijmons Evans, M. Ligtenberg, R. Oostenbrink, R. Sijmons, G. Evans, E. Woodward, E. Maher, R. Ferner, S. Aretz, I. Spier, V. Steinke-Lange, E. Holinski-Feder, E. Schröck, T. Frebourg, C. Houdayer, P. Wolkenstein, V. Bours, E. Legius, B. Poppe, K. Claes, Robin de Putter, I. Guillermo, G. Capellá, J. B. Vidal, C. Lázaro, J. Balmaña, Héctor Salvador Hernández, Carla Oliveira, M. Teixeira, S. Bajalica-Lagercrantz, E. Tham, J. Lubiński, K. Ertmańska, B. Melegh, M. Krajc, A. Blatnik, S. Peltonen, and M. Hietala. Cancer surveillance guideline for individuals with pten hamartoma tumour syndrome. European Journal of Human Genetics, 28:1387-1393, Jun 2020. URL: https://doi.org/10.1038/s41431-020-0651-7, doi:10.1038/s41431-020-0651-7. This article has 146 citations and is from a domain leading peer-reviewed journal.
(pirlog2024insightsintoclinical pages 2-4): Lorin-Manuel Pîrlog, Andrada-Adelaida Pătrășcanu, Mariela Sanda Militaru, and Andreea Cătană. Insights into clinical disorders in cowden syndrome: a comprehensive review. Medicina, 60:767, May 2024. URL: https://doi.org/10.3390/medicina60050767, doi:10.3390/medicina60050767. This article has 10 citations.

OpenScientist ▸

Cowden Syndrome: A Comprehensive Disease Characteristics Report

openscientist-autonomous 30 citations 2026-08-28T11:27:02.967792

Cowden Syndrome: A Comprehensive Disease Characteristics Report

Disease: Cowden Syndrome (CS) — a PTEN Hamartoma Tumor Syndrome (PHTS) Category: Mendelian (autosomal dominant) Suggested MONDO ID: MONDO:0016063 (Cowden disease) / part of the PHTS spectrum Report scope: Aggregated disease-level synthesis of primary literature and guideline resources (not derived from an individual EHR cohort held by this investigation)

Summary

Cowden syndrome is a rare, autosomal-dominant, multi-system hamartoma-and-cancer predisposition disorder that constitutes the prototypical member of the PTEN hamartoma tumor syndrome (PHTS) spectrum. It is caused chiefly by germline loss-of-function mutations in the PTEN tumor-suppressor gene at chromosome 10q23.31. PTEN is a dual-specificity lipid/protein phosphatase that dephosphorylates PIP3 to PIP2, thereby antagonizing the PI3K/AKT/mTOR signaling cascade. When PTEN function is lost, this growth-and-survival pathway is de-repressed, driving the hamartomas, benign overgrowth, macrocephaly, neurodevelopmental features, and markedly elevated multi-organ cancer risks that define the syndrome PMID: 26827793; PMID: 25916396.

The clinical burden is dominated by cancer risk. A large prospective study of PHTS-criteria individuals demonstrated dramatically elevated standardized incidence ratios (SIRs) for breast (SIR 25.4; lifetime ~85%), thyroid (SIR 51.1; ~35%), endometrial (SIR 42.9; ~28%), renal (SIR 30.6; ~34%), colorectal (SIR 10.3; ~9%), and melanoma (SIR 8.5; ~6%) cancers PMID: 22252256. Beyond oncologic risk, patients frequently exhibit near-universal macrocephaly, autism spectrum disorder characteristics in approximately one-quarter of carriers, a distinctive pan-gastrointestinal hamartomatous polyposis, and the pathognomonic cerebellar lesion Lhermitte-Duclos disease.

Cowden syndrome is genetically heterogeneous. A substantial minority of clinically diagnosed, PTEN-mutation-negative patients are explained by alternative mechanisms including germline KLLN promoter hypermethylation (epimutation) and germline SDHB/SDHD variants, both of which converge on a shared mitochondrial-dysfunction/elevated-succinate biochemical signature. Management is guideline-based (ERN GENTURIS / NCCN): germline genetic testing, intensive organ-specific cancer surveillance, risk-reducing surgery, and genetic counseling. Molecularly targeted PI3K/mTOR inhibition remains experimental — with encouraging anecdotal hamartoma responses (e.g., rapamycin in Lhermitte-Duclos disease) but a negative primary endpoint in the randomized everolimus trial for neurocognitive symptoms.

1. Disease Information

Overview. Cowden syndrome is a rare autosomal-dominant disorder characterized by multiple hamartomas (benign disorganized overgrowths) across ectodermal, mesodermal, and endodermal tissues, together with a substantially increased lifetime risk of breast, thyroid, endometrial, renal, and colorectal cancers plus melanoma. It is the flagship condition of the PTEN hamartoma tumor syndrome (PHTS) umbrella, which also encompasses Bannayan-Riley-Ruvalcaba syndrome (BRRS), PTEN-related Proteus syndrome, and Lhermitte-Duclos disease (adult-onset).

Key identifiers (suggested): - OMIM: 158350 (Cowden syndrome 1, PTEN-related); allelic/related PHTS entries - Orphanet: ORPHA:201 (Cowden syndrome) - MONDO: MONDO:0016063 - MeSH: Hamartoma Syndrome, Multiple (D006223) - ICD-10: Q85.8 (Other phakomatoses, not elsewhere classified) - ICD-11: LD2D.Y / relevant hamartoneoplastic syndrome code

Synonyms / alternative names: Cowden disease; multiple hamartoma syndrome; PTEN hamartoma tumor syndrome (as the encompassing molecular class); Cowden-like syndrome (for clinically compatible, PTEN-negative cases).

Information source type: This report is derived from aggregated, disease-level resources — primary literature (prospective cohorts, case series, guidelines) and curated ontologies — rather than from an individual-patient EHR dataset.

2. Etiology

Primary causal factor — genetic. The predominant cause is a germline loss-of-function mutation in PTEN (10q23.31), inherited in an autosomal-dominant fashion. "Inherited loss of function mutations in the PTEN gene were originally identified in sufferers of Cowden disease" PMID: 26827793. PTEN acts as a tumor suppressor and a brake on the PI3K/AKT/mTOR pathway; its germline haploinsufficiency, with somatic second-hit inactivation in lesions, initiates hamartoma and tumor formation.

Genetic risk factors. - Causal variant: germline PTEN pathogenic/likely-pathogenic variants (nonsense, frameshift, missense, splice-site, and promoter mutations; large deletions including 10q23 microdeletions). - Genotype–phenotype correlations: promoter mutations are associated with breast cancer, and nonsense mutations with colorectal cancer, in PTEN carriers PMID: 22252256. Catalytically inactive but stable PTEN mutants correlate with the most severe phenotypes, whereas partial-function mutants associate with milder, autism-predominant phenotypes PMID: 25916396. - Alternative loci (PTEN-negative cases): germline KLLN epimutation and SDHB/SDHD variants (see Section 4). - Candidate modifier: a SMAD7 missense variant co-occurring with a PTEN frameshift was proposed as a modifier in a family with hamartomatous polyposis and early-onset esophageal cancer PMID: 25554686.

Environmental / demographic risk factors. No specific environmental trigger causes Cowden syndrome; it is a monogenic disorder. Age and sex modulate expression: female carriers face high breast/endometrial cancer risk; cancer risks are age-dependent and cumulative. Family history is the principal actionable risk factor (cascade testing).

Protective factors. No validated genetic or environmental protective alleles are established for Cowden syndrome. Practically, "protection" is achieved through surveillance and risk-reducing surgery rather than intrinsic modifiers.

Gene–environment interactions. Evidence is limited. The mouse-model observation that simultaneous disruption of PTEN and TGF-β/SMAD signaling promotes esophageal cancer suggests pathway-level genetic interactions rather than classical gene–environment effects PMID: 25554686.

3. Phenotypes

Cowden syndrome is a pleomorphic multi-system disorder. Major phenotype domains and characteristics:

Phenotype	Type	Frequency	Onset / course	Suggested HPO
Macrocephaly	Physical/clinical sign	~100% in pediatric PHTS cohorts	Congenital/early, stable	HP:0000256
Autism spectrum disorder characteristics	Behavioral	~25% (95% CI 16–33%)	Childhood	HP:0000717
Developmental delay	Behavioral/neurodev	~58% early childhood	Childhood	HP:0001263
Trichilemmomas / mucocutaneous lesions	Physical manifestation	Very common, characteristic	Adult-onset	HP:0007592 (facial papules)
Hamartomatous GI polyps (large bowel)	Clinical/pathologic	85% of CS patients	Adult	HP:0004390
Esophageal glycogenic acanthosis	Pathologic sign	37%	Adult	HP:0100633 (esophageal lesion)
Gastric hamartomatous polyps	Pathologic	47%	Adult	HP:0004394
Duodenal hamartomatous polyps	Pathologic	20%	Adult	—
Thyroid disease (goiter/adenoma/carcinoma)	Clinical	Common	Adult	HP:0100031
Breast lesions/carcinoma	Clinical	Lifetime ~85% (women)	Adult	HP:0003002
Lhermitte-Duclos disease (cerebellar)	Clinical/imaging	Rare but pathognomonic	Adult (usually)	HP:0007266 (dysplastic cerebellar gangliocytoma)

Neurodevelopmental phenotype. A systematic review/meta-analysis "estimated pooled prevalence of ASD characteristics at 25% (95% CI 16-33%)" among individuals with constitutional PTEN mutations PMID: 34983360. In a pediatric PHTS cohort, "macrocephaly was present in 100%, 58% had developmental delays during early childhood, and 17% had an ASD diagnosis" PMID: 37090027. Macrocephaly is thus a near-universal, early, and highly sensitive sign that should prompt genetic evaluation.

Age of onset / severity / progression. Mucocutaneous and neoplastic manifestations are predominantly adult-onset, while macrocephaly and neurodevelopmental features present in childhood. Severity is highly variable even within families (variable expressivity). Cancer risk is progressive and cumulative with age.

Quality-of-life impact. Direct EQ-5D/SF-36 data specific to CS were not identified in this investigation. Qualitatively, QoL is affected by intensive lifelong surveillance burden, repeated surgeries, cancer diagnoses, GI symptoms, and neurodevelopmental/behavioral challenges. The ERN GENTURIS guideline explicitly notes the surveillance program requires significant patient commitment PMID: 42463809.

4. Genetic / Molecular Information

Causal gene. PTEN (phosphatase and tensin homolog), HGNC:9588, 10q23.31, OMIM *601728. PTEN encodes a 403-amino-acid dual-specificity phosphatase with an N-terminal phosphatase domain and a C2 (tensin-type) membrane-binding domain.

Pathogenic variants. - Genes affected: PTEN (primary); KLLN, SDHB, SDHD (subsets). - Classification: pathogenic / likely pathogenic per ACMG/AMP; VUS common for novel missense variants — a pediatric series identified four novel PTEN alterations, with 72% located in the tensin-type C2 domain PMID: 38407606. - Variant types: missense, nonsense, frameshift, splice-site, promoter, and structural (10q23 microdeletion encompassing PTEN and BMPR1A) PMID: 20815035. - Allele frequency: germline pathogenic PTEN variants are private/rare and effectively absent from population databases (gnomAD) as benign polymorphisms. - Somatic vs germline: Cowden syndrome is defined by germline variants; somatic second hits occur within lesions. Colorectal juvenile polyps in CS arise from epithelial-specific PTEN loss without a stromal PTEN requirement, per a transgenic mouse model PMID: 24200851. - Functional consequence: loss of function / haploinsufficiency (with possible dominant-negative effects for some missense mutants); catalytically inactive stable mutants produce the most severe phenotypes PMID: 25916396.

Epigenetic mechanism (KLLN epimutation). In PTEN wild-type Cowden cases, germline hypermethylation of KLLN (which shares a bidirectional promoter with PTEN) has been implicated: "Germline hypermethylation of KLLN, a gene uncovered well after the human genome project, has been linked to Cowden cancer-predisposition syndrome (CS) in PTEN wild-type cases" PMID: 26673699. KLLN maintains pericentric H3K9 trimethylation and genomic stability; its loss causes chromosomal instability, increased micronuclei, and numerical aberrations.

Succinate dehydrogenase (SDHx) variants. In 375 PTEN-mutation-negative CS/CS-like individuals, a subset with mitochondrial dysfunction carried SDH variants: "Among these, 10 (13.5%) had germline mutations/variants in SDHB (n = 3) or SDHD (7), not found in 700 controls (p < 0.001)" PMID: 18678321. SDH-variant carriers were enriched for breast, thyroid, and kidney carcinomas.

Biochemical marker — succinate. Both PTEN and SDHx mutation carriers share elevated plasma succinate: "Elevated plasma succinate was observed in 13/21 (62%) individuals with germline PTEN, SDHB, or SDHD mutations as compared with 5/32 (16%) controls (P < 0.001)" PMID: 22261759. This suggests a convergent reduction in succinate dehydrogenase activity across genotypes.

Modifier genes. Candidate: SMAD7 PMID: 25554686. Chromosomal abnormalities: 10q23 contiguous-gene microdeletions (PTEN + BMPR1A) cause infantile juvenile polyposis with overlapping features PMID: 20815035.

5. Environmental Information

Cowden syndrome is a monogenic germline disorder with no established environmental cause. There are no confirmed toxic, radiation, pollution, occupational, lifestyle, or infectious triggers. Environmental exposures relevant to sporadic cancers (e.g., radiation, carcinogens) may plausibly modulate cancer expression in carriers, but disease-specific evidence is lacking. Infectious agents: not applicable.

6. Mechanism / Pathophysiology

Core molecular pathway. PTEN is "a major negative regulator of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (mTOR) signaling pathway-controlling growth, protein synthesis, and proliferation" PMID: 25916396. PTEN dephosphorylates PIP3 → PIP2 at the plasma membrane, opposing PI3K. Loss of PTEN function elevates PIP3, activating AKT and downstream mTORC1, thereby increasing cell growth, protein synthesis, proliferation, and survival while suppressing apoptosis.

Causal chain (ASCII):

Germline PTEN LOF (haploinsufficiency)
│  + somatic 2nd hit in lesion
▼
   ↑ PIP3 at plasma membrane
▼
   ↑ PI3K → AKT activation
▼
   ↑ mTORC1 signaling
▼
 ↑ growth / protein synthesis / proliferation, ↓ apoptosis
▼
 Hamartomas (skin, GI, cerebellum), overgrowth (macrocephaly),
 neuronal hypertrophy → ASD/DD, and multi-organ carcinogenesis

Alternative/convergent axis (PTEN-negative):

KLLN promoter hypermethylation → ↓KLLN → loss of H3K9me3 → chromosomal instability
SDHB/SDHD variants → ↓SDH activity → ↑succinate (pseudohypoxia / oncometabolite)
└──────────────► shared elevated-plasma-succinate signature ◄──────────────┘

Cellular processes. Dysregulated cell growth/proliferation, reduced apoptosis, and — in the neuronal compartment — enlarged soma, dendritic hypertrophy, increased synaptic density, and altered LTP/LTD contribute to the neurodevelopmental phenotype PMID: 39812527. In PTEN-negative cases, chromosomal instability and increased micronuclei are mechanistic features of KLLN loss PMID: 26673699.

Protein dysfunction. PTEN's phosphatase activity and membrane access are conformationally regulated (open/closed forms; "eased" vs "strained" states affecting the catalytic site and C2 membrane-binding loops) PMID: 40614725. Pathogenic missense variants may impair catalysis, destabilize the protein, or hinder membrane localization.

Metabolic changes. Elevated plasma succinate across PTEN and SDHx carriers points to a shared metabolic disturbance in the TCA cycle/succinate dehydrogenase axis PMID: 22261759.

Tissue/pathway crosstalk. Epithelial PTEN loss drives colorectal juvenile polyp formation via altered epithelial–mesenchymal crosstalk, without requiring stromal PTEN loss PMID: 24200851. STAT5–PI3K/AKT cooperativity accelerates mammary tumorigenesis in a Cowden mouse model, and mammary-specific Stat5 ablation prevents carcinogenesis in PTEN-mutant mice PMID: 24469394.

Suggested ontology terms. GO:0046855 (phosphatidylinositol dephosphorylation); GO:0014065 (PI3K signaling); GO:0031929 (TOR signaling); GO:0008285 (negative regulation of cell proliferation); GO:0006915 (apoptotic process). CL terms: CL:0000066 (epithelial cell), CL:0000540 (neuron), CL:0002251 (epithelial cell of alimentary canal).

7. Anatomical Structures Affected

Organ level (primary): breast (UBERON:0000310), thyroid gland (UBERON:0002046), endometrium/uterus (UBERON:0001295 / UBERON:0000995), kidney (UBERON:0002113), colon/large intestine (UBERON:0001155), skin (UBERON:0002097), cerebellum (UBERON:0002037), gastrointestinal tract broadly (esophagus, stomach, duodenum).

Body systems involved: integumentary, endocrine, digestive, genitourinary/reproductive, nervous, and (rarely) respiratory (bronchial carcinoids reported) PMID: 38353885.

Tissue/cell level: predominantly epithelial tissue (breast ductal, thyroid follicular, colonic/gastric epithelium, trichilemmal skin epithelium) plus mesenchymal/stromal components in GI hamartomas (lymphoid, lipomatous, ganglioneuromatous elements were common in the 43-patient cohort) PMID: 31273317. Cerebellar involvement features dysplastic ganglion/granule neurons (Lhermitte-Duclos).

Suggested CL terms: CL:0002327 (mammary gland epithelial cell), CL:0002258 (thyroid follicular cell), CL:0011108 (colonic epithelial cell), CL:0000121 (Purkinje cell), CL:0000540 (neuron).

Subcellular level: plasma membrane (GO:0005886) where PTEN acts on PIP3; nucleus (PTEN nuclear functions in genomic stability); mitochondria (GO:0005739) implicated via SDHx/succinate metabolism.

Localization / lateralization: lesions are typically multifocal and bilateral (e.g., bilateral breast disease, bilateral GI polyposis). Lhermitte-Duclos lesions are often unilateral cerebellar but can be diffuse PMID: 27932596.

8. Temporal Development

Onset. Macrocephaly is congenital/early; neurodevelopmental features emerge in childhood; mucocutaneous lesions and neoplasia are predominantly adult-onset. Overall course is chronic and lifelong with an insidious onset.

Progression. Benign hamartomas are typically slow-growing/stable, but carry premalignant potential in some tissues; cancer risk is progressive and age-cumulative. Colorectal juvenile polyps can undergo dysplastic transformation to carcinoma PMID: 24200851. Lhermitte-Duclos disease is slow-growing but can cause obstructive hydrocephalus and brainstem compression requiring intervention PMID: 27932596.

Patterns / critical periods. No spontaneous remission of the underlying genetic disorder occurs. Critical intervention windows include childhood (early diagnosis via macrocephaly to enable surveillance) and the adult decades of peak cancer incidence, when surveillance and risk-reducing surgery are most impactful.

9. Inheritance and Population

Inheritance. Autosomal dominant. Penetrance is high but incomplete and age-dependent; expressivity is highly variable even within families PMID: 26827793. A significant proportion of cases are de novo. Germline mosaicism and founder effects are not prominent features. Consanguinity is not a driver (dominant disorder).

Epidemiology. Cowden syndrome is rare; commonly cited prevalence estimates are on the order of ~1 in 200,000–250,000, though this is likely an underestimate given variable expressivity and underdiagnosis. Precise incidence figures were not established in this investigation.

Population demographics. No strong ethnic predilection is established. Sex influences expression: female carriers bear high breast and endometrial cancer risk. Pediatric presentation is dominated by macrocephaly and neurodevelopmental features; adult presentation by mucocutaneous lesions and neoplasia.

Genotype–geography of variants: PTEN variants are private; no dominant founder variant identified.

10. Diagnostics

Clinical diagnostic criteria. Diagnosis uses established PTEN hamartoma tumor syndrome / Cowden syndrome clinical criteria (2013 revision) combining pathognomonic, major, and minor criteria; the Cleveland Clinic PTEN risk calculator estimates the probability of a PTEN mutation to guide testing (e.g., an 82–98% predicted probability triggered testing in one case) PMID: 37680909; PMID: 39044874.

Genetic testing (recommended, definitive). Germline PTEN sequencing plus deletion/duplication analysis is the primary test. Multi-gene hereditary cancer/polyposis panels and, in PTEN-negative cases, evaluation for KLLN methylation and SDHB/SDHD variants are appropriate. Chromosomal microarray detects 10q23 microdeletions. In pediatrics, targeted/stepwise testing is advised because of autonomy and psychosocial considerations PMID: 42353760. Significant macrocephaly in a child should prompt a genetic study for early diagnosis PMID: 38407606.

Imaging. Thyroid ultrasound; breast MRI/mammography; endometrial and renal imaging; brain MRI shows the pathognomonic cerebellar "tiger-stripe" pattern of Lhermitte-Duclos disease on T2-weighted images PMID: 40763010. Brain 18F-FDG PET can complement MRI to characterize neuropsychiatric/movement features PMID: 35006113.

Endoscopy / pathology. Upper and lower GI endoscopy reveals characteristic lesions; histopathology of hamartomatous polyps with mixed stromal (lymphoid, lipomatous, ganglioneuromatous) elements and esophageal glycogenic acanthosis is diagnostically suggestive PMID: 31273317; PMID: 28901964.

Candidate biomarker. Elevated plasma succinate distinguishes PTEN/SDHx carriers from controls and may serve as an adjunct biochemical marker PMID: 22261759.

Differential diagnosis. Other PHTS entities (BRRS, Proteus), juvenile polyposis syndrome (SMAD4/BMPR1A), Peutz-Jeghers syndrome (STK11), other macrocephaly-ASD monogenic conditions, and sporadic hamartomatous polyps PMID: 28901964; PMID: 40282429.

Screening. Cascade genetic testing of at-risk relatives is standard once a familial variant is identified.

11. Outcome / Prognosis

Cancer-driven prognosis. The prognosis is dominated by lifetime cancer risk. The landmark prospective study reported: "Elevated SIRs were found for carcinomas of the breast [25.4, 95% confidence interval (CI), 19.8-32.0], thyroid (51.1, 38.1-67.1), endometrium (42.9, 28.1-62.8), colorectum (10.3, 5.6-17.4), kidney (30.6, 17.8-49.4), and melanoma (8.5, 4.1-15.6)" PMID: 22252256.

Cancer	SIR	Estimated lifetime risk
Breast	25.4	~85.2%
Thyroid	51.1	~35.2%
Endometrial	42.9	~28.2%
Kidney	30.6	~33.6%
Colorectal	10.3	~9.0%
Melanoma	8.5	~6.0%

Morbidity/function. Neurodevelopmental features (ASD ~25%, developmental delay ~58% in pediatric cohorts) and repeated surgical/surveillance interventions contribute to disability and QoL impact PMID: 34983360; PMID: 37090027. Lhermitte-Duclos disease can cause life-threatening hydrocephalus/brainstem compression PMID: 27932596.

Prognostic factors. Genotype (promoter mutation → breast cancer; nonsense → colorectal cancer), sex, age, and adherence to surveillance influence outcomes PMID: 22252256. With early diagnosis and guideline surveillance, many cancers are detected early and are treatable, substantially improving outcomes.

12. Treatment

Overall strategy. There is no cure; management centers on surveillance, early cancer detection, and risk-reducing surgery, per ERN GENTURIS and NCCN guidelines PMID: 42463809.

Surgical/interventional. Cancer-directed surgery (e.g., thyroidectomy, mastectomy, hysterectomy), consideration of risk-reducing mastectomy/hysterectomy in high-risk carriers, polypectomy, and neurosurgical resection/decompression for symptomatic Lhermitte-Duclos disease PMID: 40469941; PMID: 36131570.

Targeted therapy — mTOR inhibition (experimental). Because PTEN loss de-represses mTOR, mTOR inhibitors are mechanistically rational (NCIT: everolimus, sirolimus/rapamycin). - Anecdotal success: In infantile Lhermitte-Duclos disease where surgery was not feasible, rapamycin produced dramatic improvement: "Within 5 months, our patient has become responsive to her surroundings and had return of spontaneous breathing. Repeat magnetic resonance imaging (MRI) reveals lack of brainstem compression or distortion of pituitary stalk. Rapamycin should be considered in cases of Lhermitte-Duclos disease where surgical removal may not be an option" PMID: 27932596. - RCT — negative primary endpoint: In a phase II randomized double-blind placebo-controlled trial of everolimus for neurocognitive symptoms in PHTS (n=46), "Changes in the primary endpoint between groups from baseline to Month 6 were not apparent (Cohen's d = -0.10, P = 0.518). However, several measures were associated with modest effect sizes (≥0.2) in the direction of improvement, including measures of nonverbal IQ, verbal learning, autism symptoms, motor skills, adaptive behavior and global improvement" PMID: 35594551. GI adverse events were more common with everolimus (P<0.001).

Pharmacogenomics / personalized medicine. Genotype-guided surveillance intensity is emerging (promoter vs nonsense correlations); no validated CS-specific pharmacogenomic dosing exists.

Supportive/rehabilitative. Neurodevelopmental support (behavioral, speech, occupational therapy) for affected children; symptom management for GI disease.

Suggested NCIT terms: Everolimus (C48387), Sirolimus/Rapamycin (C1212), Mastectomy (C15277), Thyroidectomy (C15400), Genetic Counseling (C15315).

13. Prevention

Primary prevention. Not applicable at the level of preventing the germline disorder; genetic counseling and reproductive options (preimplantation/prenatal diagnosis) can prevent transmission.

Secondary prevention (core of management). Intensive organ-specific cancer surveillance for early detection. The ERN GENTURIS guideline states: "PTEN hamartoma tumour syndrome (PHTS) is a diverse multi-system disorder predisposing to a high hereditary risk of breast, thyroid, endometrial, and a moderate risk of renal, and colorectal cancer and skin melanoma" and recommends coordinated multidisciplinary surveillance covering these organs PMID: 42463809. Typical elements: annual thyroid ultrasound, breast MRI/mammography, endometrial and renal surveillance, dermatologic exam, and colonoscopy.

Tertiary prevention. Risk-reducing surgery in high-risk carriers; treatment of premalignant polyps; management of Lhermitte-Duclos complications.

Counseling. Genetic counseling and cascade testing of relatives are essential; the guideline emphasizes the substantial patient commitment required and the need for prospective evaluation of surveillance effectiveness PMID: 42463809.

Immunization / public health / infectious prophylaxis: not applicable.

14. Other Species / Natural Disease

Taxonomy / orthologs. PTEN is highly conserved. Human PTEN (NCBI Gene 5728) has a mouse ortholog Pten (NCBI Gene 19211, on mouse chromosome 19). PTEN "encodes a protein... Located on chromosome 10 in humans and chromosome 19 in mice" PMID: 39812527.

Natural disease in animals. Cowden syndrome as a defined germline hereditary syndrome is a human condition; no equivalent naturally occurring hereditary syndrome is established in companion animals. However, PTEN loss/reduced expression is documented in canine gliomas, paralleling human tumor biology: reduced PTEN immunopositivity occurred in a substantial fraction of canine gliomas, "in line with those reported in human gliomas" PMID: 39061577 — relevant to comparative oncology rather than to inherited CS.

Comparative biology. The deep evolutionary conservation of PTEN and the PI3K/AKT/mTOR axis underlies the utility of model organisms. Zoonotic potential: not applicable.

15. Model Organisms

Mouse models (principal). - Epithelial-specific Pten deletion recapitulates colorectal juvenile polyposis: "we find epithelial-specific PTEN deletion to cause formation of juvenile polyps in the colorectum... these lesions closely recapitulate all of the characteristic histopathological features of juvenile polyps seen in patients with CS, including stromal alterations and dysplastic transformation to colorectal carcinoma" PMID: 24200851. This model demonstrated stromal PTEN loss is not a prerequisite and validated altered epithelial–mesenchymal crosstalk. - Mammary Cowden model: constitutive Stat5 activation cooperates with Pten loss to accelerate mammary tumors, and "mammary gland-specific ablation of Stat5 is sufficient to prevent mammary carcinogenesis in a genuine mouse model for Cowden syndrome" PMID: 24469394. - Neuronal Pten models reproduce enlarged soma, dendritic hypertrophy, increased synaptic density, altered LTP/LTD, and deficits in learning/memory and social behavior — recapitulating the macrocephaly/ASD phenotype PMID: 39812527.

Model types available: conditional (tissue-specific Cre) knockouts, transgenic, and germline heterozygous Pten+/− mice. Applications: studying carcinogenesis, hamartoma formation, neurodevelopmental mechanisms, and mTOR-inhibitor efficacy. Limitations: single-tissue conditional models capture individual manifestations but not the full multi-system syndrome; species differences in cancer spectrum and lifespan limit direct translation.

Resources: MGI (Pten), IMPC/IMSR for mouse alleles.

Mechanistic Model / Interpretation

Cowden syndrome is best understood as a PTEN-dosage disease with a convergent metabolic/genomic-instability tail. The dominant axis is germline PTEN haploinsufficiency plus somatic second hits, releasing the PI3K/AKT/mTOR brake to drive hamartomatous overgrowth, neuronal hypertrophy (macrocephaly, ASD), and multi-organ carcinogenesis. Genotype tunes phenotype: catalytically dead-but-stable mutants → severe; partial-function → milder/ASD-predominant; promoter mutations → breast; nonsense → colorectal.

A parallel, smaller stream explains PTEN-negative "Cowden-like" cases: KLLN epimutation (genomic instability via loss of pericentric H3K9me3) and SDHx variants (mitochondrial dysfunction). Remarkably, both PTEN and SDHx carriers share an elevated-succinate signature, hinting at a metabolic node connecting otherwise distinct genotypes — a potential unifying biomarker and therapeutic hypothesis.

         ┌──────────────── COWDEN SYNDROME ────────────────┐
   PTEN LOF ─────► PI3K/AKT/mTOR ▲ ──► hamartomas, macrocephaly, cancers
   KLLN methylation ─► genomic instability ─┐
   SDHB/SDHD variants ─► ↓SDH ─► ↑succinate ─┴─► shared biochemical signature
         └──────────────────────────────────────────────────┘
   Management: surveillance + risk-reducing surgery + counseling
   Experimental: mTOR inhibition (hamartoma responses; neurocog RCT negative)

Evidence Base

PMID	Contribution	Role
22252256	Prospective SIRs and lifetime cancer risks (breast, thyroid, endometrial, renal, colorectal, melanoma)	Supports cancer-risk profile (F001)
26827793	PTEN germline LOF as cause; phenotype prediction	Supports etiology (F002)
25916396	PTEN as PI3K/AKT/mTOR regulator; genotype–severity	Mechanism (F002)
34983360	ASD prevalence 25% meta-analysis	Neuro phenotype (F003)
37090027	Macrocephaly 100%, DD 58% pediatric	Neuro phenotype (F003)
31273317	GI polyposis spectrum, 43-patient cohort	GI phenotype (F004)
42463809	ERN GENTURIS surveillance guideline	Prevention/management (F005)
27932596	Rapamycin response in Lhermitte-Duclos	Targeted therapy (F006)
35594551	Everolimus RCT (negative primary endpoint)	Targeted therapy (F007)
26673699	KLLN epimutation & genomic instability	Heterogeneity (F008)
18678321	SDHB/SDHD variants in PTEN-negative CS	Heterogeneity (F008)
22261759	Elevated plasma succinate biomarker	Biomarker (F009)
24200851	Epithelial Pten-KO colorectal polyp mouse model	Model organism
24469394	Stat5/PI3K Cowden mammary mouse model	Model organism
39812527	PTEN in CNS; neuronal phenotypes; mouse ortholog	Mechanism/model
40614725	PTEN conformational regulation	Protein dysfunction
25554686	PTEN frameshift + SMAD7 modifier; esophageal cancer	Modifier/etiology
39061577	PTEN loss in canine gliomas	Comparative biology

Limitations and Knowledge Gaps

QoL data: No CS-specific EQ-5D/SF-36/PROMIS metrics were identified; QoL impact is described qualitatively.
Epidemiology precision: Prevalence/incidence figures are approximate and likely underestimated; no primary registry-derived incidence was verified in this investigation.
Surveillance effectiveness: The ERN GENTURIS guideline itself notes the need for prospective evaluation of whether intensive surveillance improves survival PMID: 42463809.
Targeted therapy uncertainty: mTOR-inhibitor benefit rests on anecdotes for hamartomas plus a negative primary RCT endpoint for neurocognition; efficacy for cancer prevention is unproven.
PTEN-negative subsets: KLLN and SDHx contributions come from single-center studies requiring independent replication; the mechanistic link between succinate elevation and PTEN loss remains hypothesis-level.
Genotype–phenotype: Correlations (promoter→breast, nonsense→colorectal) are associations that need validation in independent cohorts.

Proposed Follow-up Experiments / Actions

Prospective surveillance outcome study — quantify whether guideline surveillance reduces cancer mortality in PHTS, addressing the explicit ERN GENTURIS gap.
Succinate biomarker validation — replicate elevated plasma succinate as a diagnostic/monitoring biomarker across PTEN, KLLN, and SDHx subgroups in a larger, controlled cohort.
Mechanistic dissection of the PTEN–succinate link — test whether PTEN loss lowers SDH catalytic activity, potentially unifying the PTEN and SDHx metabolic phenotypes.
Genotype-stratified surveillance trial — prospectively test intensified organ-specific screening guided by variant class (promoter/nonsense/missense).
Targeted-therapy trials with tumor endpoints — evaluate mTOR/PI3K inhibitors for hamartoma burden and cancer prevention (not just neurocognition), with biomarker-based patient selection.
Registry-based epidemiology — derive robust prevalence, incidence, penetrance, and de novo rates from multinational PHTS registries.

Report compiled from 9 confirmed findings and 38 reviewed papers over 5 investigation iterations. Evidence types span human clinical cohorts, guideline consensus, model-organism studies, in vitro/structural work, and comparative pathology.

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Outcome	Count
References checked	30
Resolved	30
Unresolved (possible confabulation)	0
Unverifiable	0
Quoted claims checked	13
Quoted claims found in source	12
Quoted claims not found in source	1
References weighed for topical relevance	30
On topic	20
Off topic	0

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Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

PMID:22252256: "Elevated SIRs were found for carcinomas of the breast [25.4, 95% confidence interval (CI), 19.8-32.0], thyroid (51.1, 38.1-67.1), endometrium (42.9, 28.1-62.8), colorectum (10.3, 5.6-17.4), kidney (30.6, 17.8-49.4), and melanoma (8.5, 4.1-15.6)"
closest text in source: "Elevated SIRs were found for carcinomas of the breast [25.4, 95% confidence interval (CI), 19.8-32.0], thyroid (51.1, 38.1-67.1), endometrium (42.9, 28.1-62.8), colorectum (10.3, 5.6-17.4), kidney (30.6, 17.8-49.4), and melanoma (8.5, 4.1-15.6)"

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Deep Research

Cowden Syndrome (PTEN Hamartoma Tumor Syndrome, PHTS): Disease Characteristics Research Report

1. Disease Information

1.1 Concise overview

1.2 Key identifiers (as available from retrieved sources)

1.3 Synonyms and alternative names

1.4 Evidence provenance (individual-level vs aggregated resources)

2. Etiology

2.1 Disease causal factors

2.2 Risk factors

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes

Quality-of-life impact (selected)

4. Genetic / Molecular Information

4.1 Causal gene(s)

4.2 Pathogenic variant classes and consequences (high-level)

4.3 Non-PTEN genetic etiologies / phenocopies

4.4 Modifier genes / genomic background

4.5 Epigenetic information

4.6 Chromosomal abnormalities

5. Environmental Information

5.1 Environmental and lifestyle factors

6. Mechanism / Pathophysiology

6.1 Core molecular pathway mechanism (upstream → downstream)

6.2 Genome integrity / DNA damage response as a contributor to pleiotropy

6.3 Immune dysregulation (emerging/variable evidence)

Suggested ontology terms

7. Anatomical Structures Affected

7.1 Organ-level involvement (primary)

7.2 Tissue/cell-level and subcellular notes

7.3 UBERON term suggestions (examples)

8. Temporal Development

8.1 Onset and progression

9. Inheritance and Population

9.1 Inheritance

9.2 Penetrance and expressivity

9.3 Epidemiology

9.4 Recent population-level genetic testing statistic

10. Diagnostics

10.1 Clinical criteria and diagnostic framework

10.2 Genetic testing approach (current understanding)

10.3 Differential diagnosis (selected)

11. Outcome / Prognosis

11.1 Cancer risk burden (statistics from cohorts)

11.2 Surveillance yield (real-world implementation data)

12. Treatment

12.1 Standard treatments

12.2 Targeted/experimental therapeutics (mechanism-informed)

13. Prevention

13.1 Surveillance (secondary prevention): key guideline recommendations

14. Other Species / Natural Disease

15. Model Organisms

Recent developments and latest research (prioritizing 2023–2024)

2023–2024 high-value sources retrieved in this run

Embedded summary artifacts

Key guideline table image (visual evidence)

Notes on evidence gaps (from retrieved sources in this run)

Cowden Syndrome: A Comprehensive Disease Characteristics Report

Summary