Pheochromocytoma and Paraganglioma

MONDO:0035540 Pathograph 21 Show in embeddings browser neuroendocrine tumor

Pheochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumors arising from chromaffin cells of the adrenal medulla (pheochromocytoma) or extra-adrenal sympathetic and parasympathetic ganglia (paraganglioma). Approximately 40% of PPGLs are hereditary, caused by germline mutations in over 20 susceptibility genes including SDHx subunits (SDHA, SDHB, SDHC, SDHD), VHL, RET, NF1, MAX, and TMEM127. PPGLs may be catecholamine-secreting, causing paroxysmal hypertension, headaches, sweating, and palpitations. Understanding the genetic basis has enabled surveillance, early detection, and emerging targeted therapies for this heterogeneous tumor group. This entry covers both the sporadic tumor entity (MONDO:0035540) and the hereditary pheochromocytoma-paraganglioma predisposition syndrome (MONDO:0017366), which is modeled here as the genetic-locus axis of `has_subtypes` (PGL1-PGL5 plus the MAX- and TMEM127-related forms) rather than as a separate Disease entry. Hereditary PPGL is mechanistically split into two transcriptional clusters: Cluster 1 (pseudohypoxic) comprising Cluster 1A (SDHx, FH - oncometabolite-driven) and Cluster 1B (VHL, EPAS1 - direct HIF-axis lesions), and Cluster 2 (kinase-signaling; RET, NF1, TMEM127, MAX). This cluster assignment predicts the secretory phenotype, the tumor location, and the metastatic risk that drive clinical surveillance.

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Classifications

Harrison's Part

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Mappings

MONDO

MONDO:0017366 hereditary pheochromocytoma-paraganglioma DisMech

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Inheritance

Autosomal dominant HP:0000006

All the established hereditary PPGL susceptibility genes are transmitted in an autosomal dominant fashion with respect to the predisposition allele, although tumor formation itself requires a somatic second hit. Penetrance is incomplete, age-dependent and strongly gene-specific, and estimates from clinically ascertained families are systematically higher than those from unbiased cascade or population testing. The figures recorded here are the ascertainment-adjusted SDHB estimates of Andrews et al. (2018), which are deliberately preferred over the widely quoted older values (for example ~50% or ~75% by age 50) precisely because those earlier estimates were derived from clinically ascertained probands. Recording the corrected numbers rather than omitting them is the point of the accompanying sdhb_penetrance_ascertainment_bias knowledge-gap discussion, which remains open because even the adjusted figures come from tertiary genetics referrals rather than a population cohort.

Autosomal dominant inheritance Penetrance: INCOMPLETE Penetrance %: SDHB carriers 23.9% by age 60 and 30.6% by age 80 (ascertainment-adjusted retrospective cohort analysis); 21.8% by age 60 by Kaplan-Meier analysis of non-probands only

Show evidence (5 references)

PMID:29386252 SUPPORT Human Clinical

"With retrospective cohort analysis to adjust for ascertainment, cumulative tumour risks for SDHB mutation carriers at ages 60 years and 80 years were 23.9% (95% CI 20.9% to 27.4%) and 30.6% (95% CI 26.8% to 34.7%)."

Source of the ascertainment-adjusted SDHB penetrance figures recorded in penetrance_percentage.

PMID:29386252 SUPPORT Human Clinical

"Overall risks of clinically apparent tumours for SDHB mutation carriers are substantially lower than initially estimated and will improve counselling of affected families."

Supports the statement that clinically ascertained penetrance estimates are systematically inflated, which is why the older figures are not recorded here.

PMID:16317055 SUPPORT Human Clinical

"However, when all mutation carriers were included (n = 112), the estimated age-related penetrance was different for SDHB vs. SDHD mutation carriers (P = 0.008)."

International SDH Consortium result establishing that penetrance is age-dependent and gene-specific, which is why penetrance is recorded per-locus on the subtype inheritance blocks rather than as a single disease-level figure.

+ 2 more references

Autosomal dominant with maternal imprinting (SDHD, SDHAF2) HP:0012275

SDHD- and SDHAF2-related disease shows a striking parent-of-origin effect: carriers who inherit the variant from their father are at high risk, while those who inherit the same variant from their mother very rarely develop tumors. Stated precisely, this is a strong bias and not an absolute law - rare, well-documented cases of disease after maternal transmission exist, so maternally inheriting carriers should still be counselled and offered surveillance rather than discharged. The HPO term 'maternal imprinting' denotes silencing of the maternally inherited copy, which is the correct orientation here; the underlying somatic event is loss of the entire maternal chromosome 11, so the phenomenon is not classical imprinting alone.

Autosomal dominant inheritance with maternal imprinting Penetrance: INCOMPLETE Penetrance %: Paternally inherited SDHD: 43.2% by age 60 (Kaplan-Meier analysis of non-probands). Maternally inherited SDHD carriers have a tumour risk approaching that of the general population.

Parent-of-origin effect: Paternal transmission required for expression in SDHD and SDHAF2 (and possibly MAX); a strong bias rather than an absolute rule, since exceptions after maternal transmission are documented.

Show evidence (4 references)

PMID:15064708 SUPPORT Human Clinical

"In SDHD (11q23)-linked families, the disease phenotype is expressed only upon paternal transmission of the mutation, consistent with maternal imprinting."

States the parent-of-origin pattern and its interpretation as maternal imprinting, matching the bound HPO term.

PMID:15064708 SUPPORT Human Clinical

"However, SDHD shows biallelic expression in brain, kidney and lymphoid tissues (Baysal et al., 2000)."

Qualifies the imprinting interpretation - SDHD is not uniformly silenced on the maternal allele, which is why the mechanism is better explained by somatic loss of maternal chromosome 11 than by classical imprinting.

PMID:20301715 SUPPORT Other

"Pathogenic variants in SDHD, SDHAF2, and possibly MAX demonstrate parent-of-origin effects and cause disease almost exclusively when they are paternally inherited"

GeneReviews statement of the parent-of-origin rule, whose wording ('almost exclusively') is the basis for stating this as a strong bias rather than an absolute law.

+ 1 more reference

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Subtypes

Pheochromocytoma

Tumors arising from the adrenal medulla chromaffin cells. Most common site of catecholamine-producing paraganglioma. Usually unilateral but bilateral in hereditary syndromes.

Sympathetic Paraganglioma

Extra-adrenal tumors arising from sympathetic ganglia along the paravertebral axis (thorax, abdomen, pelvis). Often catecholamine-secreting. SDHB mutations associated with high malignancy risk.

Parasympathetic Paraganglioma

Head and neck paragangliomas arising from parasympathetic ganglia (carotid body, jugulotympanic, vagal). Usually non-secreting. SDHD mutations common.

PGL1 - SDHD-related hereditary paraganglioma-pheochromocytoma MONDO:0008192

SDHD hgnc:10683 Autosomal dominant inheritance with maternal imprinting

SDHD (11q23) germline loss of function. The most penetrant head-and-neck paraganglioma locus, typically multifocal and frequently non-secretory. Disease is expressed almost exclusively after paternal transmission (see the inheritance section); the operative somatic event is loss of the entire maternal chromosome 11 rather than classical two-hit loss of the SDHD locus alone. Metastatic risk is substantially lower than for SDHB/PGL4.

Show evidence (1 reference)

PMID:15064708 SUPPORT Human Clinical

"In SDHD (11q23)-linked families, the disease phenotype is expressed only upon paternal transmission of the mutation, consistent with maternal imprinting."

Establishes the SDHD locus assignment (11q23) and the parent-of-origin expression pattern that defines PGL1.

PGL2 - SDHAF2-related hereditary paraganglioma MONDO:0011121

SDHAF2 hgnc:26034 Autosomal dominant inheritance with maternal imprinting

SDHAF2 (also called SDH5, 11q13) germline loss of function. SDHAF2 is an assembly factor required for flavination of the SDHA catalytic subunit, so its loss disables the SDH complex without mutating a structural subunit. The rarest of the PGL loci; presents essentially as multifocal head-and-neck paraganglioma, and like PGL1 shows parent-of-origin (paternal transmission) expression. Pheochromocytoma is uncommon in this subtype.

Show evidence (1 reference)

PMID:19628817 SUPPORT Human Clinical

"Germline loss-of-function mutations in the human SDH5 gene, located on chromosome 11q13.1, segregate with disease in a family with hereditary paraganglioma, a neuroendocrine tumor previously linked to mutations in genes encoding SDH subunits."

Original identification of SDHAF2/SDH5 as the PGL2 gene, including the 11q13.1 locus assignment.

PGL3 - SDHC-related hereditary paraganglioma-pheochromocytoma MONDO:0011544

SDHC hgnc:10682 Autosomal dominant inheritance

SDHC (1q23) germline loss of function. Predominantly head-and-neck paraganglioma, usually unifocal, with comparatively low metastatic risk. Standard (non-imprinted) autosomal dominant transmission. SDHC promoter hypermethylation - rather than germline mutation - is the usual lesion in Carney triad, which is a distinct entity.

PGL4 - SDHB-related hereditary paraganglioma-pheochromocytoma MONDO:0007273

SDHB hgnc:10681 Autosomal dominant inheritance

SDHB (1p36) germline loss of function. The clinically most consequential locus: extra-adrenal sympathetic (abdominal/thoracic) paraganglioma predominates, and SDHB carries by far the highest risk of metastatic disease of any PPGL susceptibility gene, which is why it drives the most intensive lifelong surveillance. Epigenetic silencing is most severe in SDHB-mutated tumors, offering a mechanistic explanation for that malignancy. Standard (non-imprinted) autosomal dominant transmission. Also confers risk of renal cell carcinoma and gastrointestinal stromal tumor.

Show evidence (1 reference)

PMID:15328326 SUPPORT Human Clinical

"SDHB mutation carriers have an increased frequency of malignant disease (11/32 vs 0/34, P<.001)."

Direct comparison establishing the elevated metastatic risk of SDHB carriers relative to SDHD carriers.

PGL5 - SDHA-related hereditary paraganglioma-pheochromocytoma MONDO:0013602

SDHA hgnc:10680 Autosomal dominant inheritance

SDHA (5p15) germline loss of function. SDHA encodes the flavoprotein catalytic subunit of complex II. Low-penetrance PPGL predisposition with a broad tumor spectrum including gastrointestinal stromal tumor. Biallelic (recessive) SDHA loss causes a mechanistically distinct, non-neoplastic disease - mitochondrial complex II deficiency with Leigh syndrome - which is curated separately and is not part of this tumor-predisposition subtype.

Discussions and Knowledge Gaps

What is the true age-related penetrance of SDHB pathogenic variants in carriers ascertained without a personal or family history of tumor?

KNOWLEDGE GAP OPEN sdhb_penetrance_ascertainment_bias

Attached to

pathophysiology#Metastatic Progression

Early penetrance and metastatic-risk estimates for SDHB were derived from clinically ascertained index cases and affected families, which systematically overestimates risk. Later cascade-testing and population series have revised penetrance substantially downward. This matters practically rather than academically: surveillance intensity, the age at which imaging starts, and the counselling given to an unaffected relative who tests positive all depend on which estimate is used. The gap is widening as incidental identification of SDHB variants on broad panels becomes common.

Proposed experiments

Unbiased population-ascertained SDHB carrier penetrance cohort

exp_sdhb_unbiased_population_penetrance_cohort

Prospective follow-up of unselected SDHB carriers identified through population-scale biobank sequencing rather than clinical referral, with standardized imaging, reporting age-specific cumulative incidence separately for carriers with and without a family history.

Does molecular cluster assignment (Cluster 1A SDHx/FH versus Cluster 1B VHL/EPAS1 versus Cluster 2 kinase-signaling) predict response to HIF-2alpha inhibition with belzutifan?

KNOWLEDGE GAP OPEN cluster_prediction_of_belzutifan_response

Attached to

pathophysiology#Pseudohypoxia and HIF Activation

The mechanistic rationale for belzutifan is that Cluster 1 tumors are driven by HIF-2alpha, which predicts that Cluster 1 disease should respond preferentially and that Cluster 2 disease should not. The registrational phase 2 trial was not stratified or powered to test this, reporting a 26% objective response rate across an unselected advanced-PPGL population. If the prediction holds, cluster assignment becomes a treatment-selection biomarker; if responses are distributed evenly across clusters, the assumed mechanism of benefit in PPGL is incomplete. This is an explicitly open question in the current literature.

Proposed experiments

Belzutifan response stratified by molecular cluster

exp_belzutifan_response_by_molecular_cluster

Prespecified biomarker analysis of response by germline and somatic driver and by transcriptional cluster within belzutifan-treated cohorts, ideally pooled across trials to reach adequate numbers in the smaller genotype groups.

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Pathophysiology

Succinate Dehydrogenase Complex Dysfunction

Mutations in SDHx genes (SDHA, SDHB, SDHC, SDHD, SDHAF2) impair mitochondrial complex II function, leading to succinate accumulation. Succinate acts as an oncometabolite, inhibiting alpha-ketoglutarate-dependent dioxygenases and causing pseudohypoxia and epigenetic dysregulation.

chromaffin cell CL:0000166

succinate dehydrogenase activity GO:0000104 ↓ DECREASED

adrenal gland UBERON:0002369

Downstream

Succinate Accumulation and Oncometabolite Signaling Loss of complex II catalytic activity blocks oxidation of succinate to fumarate, so succinate accumulates to millimolar concentrations.

Show evidence (1 reference)

PMID:33112834 SUPPORT Human Clinical

"SDHx mutations lead to the accumulation of succinate, which acts as an oncometabolite by inhibiting iron(II) and alpha-ketoglutarate-dependent dioxygenases thereby regulating the cell's hypoxic response and epigenetic processes."

This abstract connects SDHx mutations to succinate accumulation and dioxygenase inhibition, matching the described mechanism.

Succinate Accumulation and Oncometabolite Signaling

Succinate accumulating behind the complex II block acts as an oncometabolite. Because succinate is a structural analog of 2-oxoglutarate (alpha-ketoglutarate), it competitively inhibits the large family of 2-oxoglutarate-dependent dioxygenases. This single biochemical event is the branch point from which both arms of Cluster 1A pathology derive: inhibition of the TET DNA 5-methylcytosine dioxygenases and JmjC histone demethylases produces the hypermethylator phenotype, while inhibition of the HIF prolyl hydroxylases (PHDs) produces pseudohypoxia. The same logic applies to fumarate in FH-mutant tumors, which display an 'SDH-like' epigenetic phenotype.

chromaffin cell CL:0000166

2-oxoglutarate-dependent dioxygenase activity GO:0016706 ↓ DECREASED

Downstream

DNA and Histone Hypermethylator Phenotype Inhibition of TET dioxygenases and JmjC histone demethylases blocks demethylation, producing genome-wide hypermethylation.

Pseudohypoxia and HIF Activation Inhibition of HIF prolyl hydroxylases prevents HIF-alpha hydroxylation and VHL-mediated degradation.

Show evidence (1 reference)

PMID:33112834 SUPPORT Other

States the competitive-inhibition mechanism and that it drives both the hypoxic-response and epigenetic arms.

DNA and Histone Hypermethylator Phenotype

SDHx-mutant paragangliomas form a distinct methylome cluster characterized by genome-wide DNA and histone hypermethylation (a CpG island methylator phenotype). Succinate-driven inhibition of 2-oxoglutarate-dependent TET and JmjC demethylases silences genes governing neuroendocrine differentiation and establishes a migratory phenotype. Epigenetic silencing is most severe in SDHB-mutant tumors, which provides the leading mechanistic explanation for why SDHB carries the highest metastatic risk. The phenotype is pharmacologically reversible with a demethylating agent in model systems.

epigenetic regulation of gene expression GO:0040029 ⚠ ABNORMAL

DNA 5-methylcytosine dioxygenase activity GO:0070579 ↓ DECREASED histone demethylase activity GO:0032452 ↓ DECREASED

Downstream

Metastatic Progression Hypermethylation-driven silencing of differentiation genes and acquisition of a migratory phenotype, most marked in SDHB-mutant tumors.

Noradrenergic and Dopaminergic Secretory Phenotype Downregulation of neuroendocrine differentiation genes, including the PNMT-dependent maturation required for epinephrine synthesis.

Show evidence (2 references)

PMID:23707781 SUPPORT In Vitro

"Succinate accumulation in SDH-deficient mouse chromaffin cells led to DNA hypermethylation by inhibition of 2-OG-dependent histone and DNA demethylases and established a migratory phenotype reversed by decitabine treatment."

Direct experimental demonstration that succinate inhibits 2-OG-dependent demethylases and produces the hypermethylator/migratory phenotype.

PMID:23707781 SUPPORT Human Clinical

"Epigenetic silencing was particularly severe in SDHB-mutated tumors, potentially explaining their malignancy."

Links severity of the hypermethylator phenotype specifically to SDHB and to metastatic behavior.

Pseudohypoxia and HIF Activation

Constitutive stabilization of hypoxia-inducible factors (chiefly HIF-2alpha) under normoxic conditions - a 'pseudohypoxic' state. Cluster 1A reaches it by oncometabolite inhibition of the prolyl hydroxylases; Cluster 1B reaches the same node directly, either by loss of the VHL E3 ligase that recognizes hydroxylated HIF-alpha, or by gain-of-function EPAS1/HIF2A variants that escape hydroxylation. The convergence of these distinct lesions on one node is what makes HIF-2alpha a shared druggable target across Cluster 1.

response to hypoxia GO:0001666 ↑ INCREASED peptidyl-proline hydroxylation to 4-hydroxy-L-proline GO:0018401 ↓ DECREASED

Downstream

Angiogenic and Glycolytic Tumor Program Stabilized HIF drives transcription of VEGF and glycolytic enzyme genes.

Show evidence (2 references)

PMID:15652751 SUPPORT In Vitro

"succinate, which accumulates as a result of SDH inhibition, inhibits HIF-alpha prolyl hydroxylases in the cytosol, leading to stabilization and activation of HIF-1alpha."

The foundational demonstration that succinate inhibits the PHDs, defining the pseudohypoxia mechanism.

PMID:22931260 SUPPORT Human Clinical

"Here we report two novel somatic gain-of-function mutations in the gene encoding hypoxia-inducible factor 2α (HIF2A) in two patients, one presenting with paraganglioma and the other with paraganglioma and somatostatinoma, both of whom had polycythemia."

Establishes the Cluster 1B EPAS1/HIF2A route to the same pseudohypoxic node, with the polycythemia that distinguishes it clinically.

Angiogenic and Glycolytic Tumor Program

HIF-driven transcription of VEGF, PDGF, EPO and glycolytic enzymes produces the characteristically hypervascular PPGL and a glycolytic metabolic shift. This node is the rationale for both anti-angiogenic multikinase inhibitors and for 18F-FDG PET avidity, which is highest in SDHx-related disease.

angiogenesis GO:0001525 ↑ INCREASED glycolytic process GO:0006096 ↑ INCREASED

Downstream

Chromaffin Cell Tumorigenesis Sustained angiogenic and metabolic support permits expansion of the neoplastic chromaffin-cell clone.

Show evidence (2 references)

PMID:39735644 SUPPORT Human Clinical

"the pseudohypoxic tumor environment stimulates VEGF synthesis, promoting angiogene sis"

States the pseudohypoxia-to-VEGF-to-angiogenesis link that defines this node and its tumor_angiogenesis conformance. (The space inside 'angiogene sis' is a PDF line-break artifact of the cached full text and is reproduced verbatim so the snippet matches the cache.)

PMID:39735644 SUPPORT Human Clinical

"Sunitinib, which inhibits VEGF1, VEGF2, VEGF3, PDGF-alpha, PDGF-beta, c- kit, fms-related tyrosine kinase 3, and RET proto-oncogene receptors, has demonstrated potential in reducing angiogenesis and tumor cell growth."

Confirms this node is the actionable target of the antiangiogenic multikinase inhibitors that declare target_mechanisms against it. (The space inside 'c- kit' is a PDF line-break artifact of the cached full text, reproduced verbatim.)

Kinase Signaling Activation

The Cluster 2 arm, mechanistically distinct from pseudohypoxia. RET gain-of-function (MEN2), NF1 loss (neurofibromin is a RAS GTPase-activating protein), TMEM127 loss (a negative regulator of mTOR) and MAX loss (the obligate MYC dimerization partner) converge on RAS-MAPK and PI3K-AKT-mTOR signaling. Cluster 2 tumors are typically adrenal, well-differentiated, and adrenergic-secreting, with a low metastatic rate - the clinical mirror image of SDHB disease.

TOR signaling GO:0031929 ↑ INCREASED

protein tyrosine kinase activity GO:0004713 ↑ INCREASED

Downstream

Chromaffin Cell Tumorigenesis Constitutive mitogenic signaling drives chromaffin-cell proliferation and survival.

Adrenergic Secretory Phenotype Cluster 2 tumors retain a mature adrenal chromaffin phenotype with PNMT expression, so they synthesize epinephrine.

Show evidence (1 reference)

PMID:20154675 SUPPORT In Vitro

"Accordingly, in vitro gain-of-function and loss-of-function analyses indicate that TMEM127 is a negative regulator of mTOR."

Establishes the mTOR axis as the mechanism of the TMEM127 Cluster 2 subtype.

Somatic Loss of Maternal Chromosome 11

The mechanistic explanation for the SDHD/SDHAF2 parent-of-origin effect. Both genes lie on chromosome 11 (SDHD at 11q23, SDHAF2 at 11q13). Tumorigenesis requires loss of the wild-type maternal allele, and in SDHD-linked tumors the event is loss of the entire maternal chromosome 11 rather than a focal second hit. Because that single event must remove the wild-type copy, a mutation inherited from the mother is not usually unmasked, and disease is expressed almost exclusively after paternal transmission. Note that this is not simple classical imprinting: SDHD shows biallelic expression in several normal tissues, and the loss of the co-deleted imprinted 11p15 region is thought to contribute.

adrenal medulla UBERON:0001236

Downstream

Succinate Dehydrogenase Complex Dysfunction Loss of the wild-type maternal allele completes biallelic SDHD inactivation in the tumor precursor cell.

Show evidence (1 reference)

PMID:15064708 SUPPORT Human Clinical

"Here we demonstrate exclusive loss of the entire maternal chromosome 11 in SDHD-linked paragangliomas and phaeochromocytomas"

Direct demonstration of the somatic event underlying the parent-of-origin pattern in SDHD-linked disease.

Chromaffin Cell Tumorigenesis

Clonal expansion of neoplastic chromaffin or glomus cells to form a pheochromocytoma (adrenal medulla) or paraganglioma (extra-adrenal sympathetic chain, or parasympathetic head-and-neck paraganglia). Genotype largely predicts site: SDHB favors extra-adrenal abdominal/thoracic sympathetic tumors, SDHD and SDHAF2 favor multifocal head-and-neck parasympathetic tumors, and Cluster 2 genes favor bilateral adrenal pheochromocytoma.

chromaffin cell CL:0000166

adrenal medulla UBERON:0001236 carotid body UBERON:0001629

Downstream

Catecholamine Hypersecretion Secretory tumors release catecholamines into the circulation independently of neural control.

Metastatic Progression A subset progresses to metastatic disease, defined by tumor at sites where chromaffin tissue is not normally present.

Show evidence (2 references)

PMID:32617052 SUPPORT Human Clinical

"Pheochromocytomas arise from chromaffin cells in the adrenal medulla, and PGLs arise from chromaffin cells in the ganglia of the autonomic nervous system."

Establishes the chromaffin-cell origin and the adrenal-versus-extra-adrenal site split that this node models.

PMID:15328326 SUPPORT Human Clinical

"Head and neck paragangliomas (10/32 vs 27/34, respectively, P<.001) and multifocal (9/32 vs 25/34, respectively, P<.001) tumors were more frequent in carriers of SDHD mutations."

Supports the genotype-predicts-site claim, contrasting SDHD head-and-neck multifocal disease with the SDHB extra-adrenal pattern.

Noradrenergic and Dopaminergic Secretory Phenotype

SDHx-related and other Cluster 1 tumors, and parasympathetic head-and-neck paragangliomas, lack or downregulate phenylethanolamine N-methyltransferase (PNMT), the cortisol-dependent enzyme that converts norepinephrine to epinephrine and which requires the adrenal cortical microenvironment. They therefore secrete norepinephrine (measured as normetanephrine) and sometimes dopamine (measured as 3-methoxytyramine) rather than epinephrine. Many head-and-neck parasympathetic paragangliomas are biochemically silent altogether and present as a painless neck mass or with cranial-nerve palsy, not with catecholamine symptoms - which is precisely why a normal metanephrine panel cannot exclude them.

catecholamine biosynthetic process GO:0042423 ⚠ ABNORMAL

Downstream

Catecholamine Hypersecretion Where the tumor is secretory, the released amine is predominantly norepinephrine and/or dopamine.

Show evidence (3 references)

PMID:32617052 SUPPORT Human Clinical

"Almost all tumors with mutations in cluster 1 are tumors with a noradrenergic biochemical phenotype. These produce norepinephrine and dopamine, not epinephrine."

Establishes the Cluster 1 noradrenergic/dopaminergic secretory phenotype that defines this node.

PMID:32617052 SUPPORT Human Clinical

"PGLs, on the other hand, are not able to synthesize epinephrine since they do not contain the PNMT enzyme. They only secrete norepinephrine."

Gives the PNMT-absence mechanism underlying the noradrenergic profile of extra-adrenal paraganglioma.

PMID:32617052 SUPPORT Human Clinical

"However, approximately 2/3 of PGLs of parasympathetic origin in the head and neck region are not endocrine active."

Supports the biochemically silent head-and-neck presentation and hence the statement that a normal metanephrine panel cannot exclude these tumors.

Adrenergic Secretory Phenotype

Cluster 2 (RET/NF1/TMEM127) and other adrenal tumors retain PNMT expression and secrete epinephrine, measured as metanephrine. The adrenergic versus noradrenergic split is the basis on which a fractionated metanephrine panel becomes genotype-informative rather than merely diagnostic: a metanephrine-predominant pattern points toward RET/NF1, a normetanephrine-predominant pattern toward VHL/SDHx, and a 3-methoxytyramine elevation toward SDHx and dopaminergic, often metastatic, disease.

catecholamine biosynthetic process GO:0042423 ↑ INCREASED

Downstream

Catecholamine Hypersecretion Epinephrine release drives the classic paroxysmal symptom triad.

Show evidence (1 reference)

PMID:32617052 SUPPORT Human Clinical

"Many of the cluster 2 mutations have adrenergic biochemical phenotype and are associated with increased epinephrine production as a result of high PNMT expression."

Establishes the Cluster 2 adrenergic secretory phenotype and its PNMT basis, the mirror image of the Cluster 1 node.

Catecholamine Hypersecretion

Secreting PPGLs produce excess catecholamines (norepinephrine, epinephrine, dopamine), causing characteristic symptoms. The catecholamine profile provides clues to underlying genetics: norepinephrine-predominant suggests SDHx/VHL, epinephrine-predominant suggests RET/NF1.

catecholamine biosynthetic process GO:0042423 ↑ INCREASED

Show evidence (1 reference)

PMID:32617052 SUPPORT Human Clinical

"The majority of PCC and sympathetic PGL are endocrine active tumors causing clinical symptoms by secreting excess catecholamines (norepinephrine, epinephrine, dopamine) and their metabolites."

Abstract notes catecholamine-secreting tumors causing clinical symptoms.

Metastatic Progression

Metastatic PPGL is defined by the presence of tumor at sites where chromaffin tissue is not normally found (bone, liver, lung, lymph node) - the WHO 2022 endocrine classification retired the benign/malignant dichotomy because all PPGL carry some metastatic potential. Risk is dominated by genotype: SDHB is the strongest predictor, with FH close behind, and both share the severe hypermethylator phenotype. Extra-adrenal primary site, larger tumor size and a dopaminergic (3-methoxytyramine-producing) biochemical profile add further risk. This node is the reason SDHB carriers receive the most intensive lifelong imaging surveillance. Germline risk is compounded by acquired somatic events: loss-of-function ATRX mutations recur specifically in SDHB-mutant tumors and are an independent outcome marker, and the resulting alternative lengthening of telomeres is a candidate therapeutic vulnerability. Somatic ATRX/TERT lesions are modeled here as a modifier of this node rather than as separate pathophysiology nodes, because they are acquired and not part of the germline predisposition axis this entry scopes.

Show evidence (3 references)

PMID:28162975 SUPPORT Human Clinical

"our analysis confirmed SDHB germline mutations, ATRX somatic mutations and Ki-67 expression as clinical outcome markers"

TCGA confirmation that somatic ATRX mutation, alongside germline SDHB, marks aggressive clinical behavior.

PMID:28162975 SUPPORT Human Clinical

"three tumors had both SDHB germline and ATRX somatic mutations, a previously reported association"

Documents the co-occurrence of germline SDHB and somatic ATRX that concentrates metastatic risk in the SDHB subgroup.

PMID:24334767 SUPPORT Human Clinical

"Remarkably, FH-deficient PCC/PGLs display the same pattern of epigenetic deregulation as SDHB-mutated malignant PCC/PGL."

Ties the shared hypermethylator phenotype of FH- and SDHB-deficient tumors to their shared metastatic tendency.

✶

Histopathology

Neuroendocrine Differentiation VERY_FREQUENT

PPGLs are neuroendocrine tumors, and the histological finding asserted here is neuroendocrine differentiation of the tumor cells (chromogranin A and synaptophysin positivity in a Zellballen nesting pattern), which is what the bound NCIT term denotes.

Show evidence (1 reference)

PMID:32617052 SUPPORT Human Clinical

"Pheochromocytomas (PCC) and paragangliomas (PGL) are rare neuroendocrine tumors."

Abstract characterizes PCC/PGL as rare neuroendocrine tumors.

Loss of SDHB Immunohistochemical Staining

SDHB immunohistochemistry is the standard triage tool that decides who needs SDHx germline sequencing. Loss of any single SDH subunit destabilizes the whole complex II heterotetramer, so SDHB protein is lost from the tumor regardless of which SDH subunit gene is mutated - SDHB staining is therefore a readout for the entire SDHx group, not just for SDHB. Granular cytoplasmic staining is retained in normal cells of the intratumoral fibrovascular network, which serves as the internal positive control. Importantly, tumors from Cluster 2 and Cluster 1B syndromes (RET/MEN2, VHL, NF1) retain SDHB staining, so the stain also discriminates SDHx disease from the other hereditary syndromes.

Show evidence (2 references)

PMID:19576851 SUPPORT Human Clinical

"SDHB protein expression was absent in all 102 phaeochromocytomas and paragangliomas with an SDHB, SDHC, or SDHD mutation, but was present in all 65 paraganglionic tumours related to multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and neurofibromatosis type 1."

Demonstrates that SDHB IHC loss marks the SDHx group as a whole and is retained in MEN2/VHL/NF1 tumors, supporting its use as a discriminating triage test.

PMID:19576851 SUPPORT Human Clinical

"The sensitivity and specificity of the SDHB immunohistochemistry to detect the presence of an SDH mutation in the prospective series were 100% (95% CI 87-100) and 84% (60-97), respectively."

Quantifies the test performance underpinning the recommendation to sequence only SDHB-negative tumors.

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Pathograph

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Phenotypes

Blood 1

Polycythemia HP:0001901

Show evidence (1 reference)

PMID:22931260 SUPPORT Human Clinical

Documents the paraganglioma-polycythemia association that characterizes the EPAS1/HIF2A subtype.

Cardiovascular 5

Hypertension VERY_FREQUENT HP:0000822

Show evidence (2 references)

PMID:17156452 SUPPORT Human Clinical

"An increase in the production of catecholamines causes symptoms (mainly headaches, palpitations and excess sweating) and signs (mainly hypertension, weight loss and diabetes) reflecting the effects of epinephrine and norepinephrine on alpha- and beta-adrenergic receptors."

Abstract lists hypertension among catecholamine-related signs.

PMID:39735644 SUPPORT Human Clinical

"Signs % of presence Sustained hypertension 48% Paroxysmic hypertension 44% Hypertension 92%"

Consecutive rows of the clinical-signs-frequency table (Table 1) of a 2024 scoping review; the Hypertension row reads 92%, which falls in the VERY_FREQUENT band (80-99%).

Palpitations FREQUENT HP:0001962

Show evidence (2 references)

PMID:39735644 SUPPORT Human Clinical

"Headache 59% Palpitations 50% Diaphoresis 50%"

Consecutive rows of the symptom-frequency table (Table 1) of a 2024 scoping review; the Palpitations row reads 50%, which falls in the FREQUENT band (30-79%).

PMID:17156452 SUPPORT Human Clinical

Abstract explicitly names palpitations as a leading symptom of catecholamine excess in PPGL.

Syncope FREQUENT HP:0001279

Show evidence (1 reference)

PMID:39735644 SUPPORT Human Clinical

"Weight loss 30% Syncope episodes 40% Anxiety 19%"

Consecutive rows of the symptom-frequency table (Table 1) of a 2024 scoping review; the Syncope episodes row reads 40%, which falls in the FREQUENT band (30-79%).

Tachycardia OCCASIONAL HP:0001649

Show evidence (1 reference)

PMID:39735644 SUPPORT Human Clinical

"Hypertension 92% Tachycardia 15% Orthostatic hypotension 12%"

Consecutive rows of the clinical-signs-frequency table (Table 1) of a 2024 scoping review; the Tachycardia row reads 15%, which falls in the OCCASIONAL band (5-29%).

Orthostatic Hypotension OCCASIONAL HP:0001278

Show evidence (1 reference)

PMID:39735644 SUPPORT Human Clinical

"Hypertension 92% Tachycardia 15% Orthostatic hypotension 12%"

Consecutive rows of the clinical-signs-frequency table (Table 1) of a 2024 scoping review; the Orthostatic hypotension row reads 12%, which falls in the OCCASIONAL band (5-29%).

Ear 3

Dizziness FREQUENT Vertigo HP:0002321

Show evidence (1 reference)

PMID:39735644 SUPPORT Human Clinical

"Symptoms % of presence Dizziness 67%"

Consecutive rows of the symptom-frequency table (Table 1) of a 2024 scoping review; the Dizziness row reads 67%, which falls in the FREQUENT band (30-79%).

Pulsatile Tinnitus HP:0000360

Show evidence (1 reference)

PMID:21691058 SUPPORT Human Clinical

"The most common symptoms were hoarseness, tinnitus and hearing loss."

Retrospective series of 22 vagal paragangliomas identifying tinnitus among the most common presenting symptoms.

Hearing Loss Hearing impairment HP:0000365

Show evidence (1 reference)

PMID:21691058 SUPPORT Human Clinical

"The most common symptoms were hoarseness, tinnitus and hearing loss."

Identifies hearing loss as a leading presenting symptom of vagal paraganglioma.

Endocrine 2

Pheochromocytoma VERY_FREQUENT HP:0002666

Show evidence (2 references)

PMID:32617052 SUPPORT Human Clinical

"Pheochromocytomas arise from chromaffin cells in the adrenal medulla, and PGLs arise from chromaffin cells in the ganglia of the autonomic nervous system."

Defines the adrenal-medullary origin of pheochromocytoma.

PMID:32617052 SUPPORT Human Clinical

"Of these neuroendocrine tumors, 80-85% is PCCs, and 15-20% is PGLs."

Quantifies pheochromocytoma as the predominant presentation, supporting the VERY_FREQUENT frequency band.

Diabetes Mellitus HP:0000819

Show evidence (1 reference)

PMID:17156452 SUPPORT Human Clinical

Lists diabetes among the cardinal signs produced by catecholamine excess.

Integument 2

Diaphoresis FREQUENT Hyperhidrosis HP:0000975

Show evidence (2 references)

PMID:39735644 SUPPORT Human Clinical

"Palpitations 50% Diaphoresis 50% Weight loss 30%"

Consecutive rows of the symptom-frequency table (Table 1) of a 2024 scoping review; the Diaphoresis row reads 50%, which falls in the FREQUENT band (30-79%).

PMID:17156452 SUPPORT Human Clinical

Abstract explicitly names excess sweating as a leading symptom of catecholamine excess in PPGL.

Pallor HP:0000980

Metabolism 1

Hyperglycemia HP:0003074

Show evidence (1 reference)

PMID:39735644 SUPPORT Human Clinical

"Pancreas Carbohydrate intolerance due to Beta cells"

Table 1 row attributing carbohydrate intolerance to catecholamine-mediated changes in beta-cell regulation and insulin release suppression.

Nervous System 3

Headache FREQUENT HP:0002315

Show evidence (2 references)

PMID:39735644 SUPPORT Human Clinical

"Symptoms % of presence Dizziness 67% Headache 59%"

Consecutive rows of the symptom-frequency table (Table 1) of a 2024 scoping review; the Headache row reads 59%, which falls in the FREQUENT band (30-79%).

PMID:17156452 SUPPORT Human Clinical

Abstract explicitly names headache as a leading symptom of catecholamine excess in PPGL.

Anxiety OCCASIONAL HP:0000739

Show evidence (1 reference)

PMID:39735644 SUPPORT Human Clinical

"Weight loss 30% Syncope episodes 40% Anxiety 19%"

Consecutive rows of the symptom-frequency table (Table 1) of a 2024 scoping review; the Anxiety row reads 19%, which falls in the OCCASIONAL band (5-29%).

Tremor HP:0001337

Show evidence (1 reference)

PMID:39735644 SUPPORT Human Clinical

"tremor, anxiety/panic, and pallor, and older age"

Names tremor as part of the episodic sympathetic symptom presentation used to classify PPGL probability.

Growth 1

Weight Loss FREQUENT HP:0001824

Show evidence (2 references)

PMID:39735644 SUPPORT Human Clinical

"Diaphoresis 50% Weight loss 30% Syncope episodes 40%"

Consecutive rows of the symptom-frequency table (Table 1) of a 2024 scoping review; the Weight loss row reads 30%, which falls in the FREQUENT band (30-79%).

PMID:17156452 SUPPORT Human Clinical

Independent review listing weight loss among the cardinal catecholamine-mediated signs.

Other 4

Paraganglioma HP:0002668

Show evidence (2 references)

PMID:32617052 SUPPORT Human Clinical

"Paragangliomas originate from sympathetic or parasympathetic ganglia in the abdomen, thorax, and pelvis."

Defines the extra-adrenal sympathetic/parasympathetic origin.

PMID:15328326 SUPPORT Human Clinical

"Head and neck paragangliomas (10/32 vs 27/34, respectively, P<.001) and multifocal (9/32 vs 25/34, respectively, P<.001) tumors were more frequent in carriers of SDHD mutations."

Supports the genotype-site correlation, with head-and-neck and multifocal paraganglioma concentrated in SDHD carriers.

Renal Cell Carcinoma HP:0005584

Gastrointestinal Stromal Tumor Gastrointestinal stroma tumor HP:0100723

Hoarseness Dysphonia HP:0001618

Show evidence (1 reference)

PMID:21691058 SUPPORT Human Clinical

"The most common symptoms were hoarseness, tinnitus and hearing loss."

Identifies hoarseness as a leading presenting symptom of vagal paraganglioma.

🧬

Genetic Associations

SDHB (Germline Loss-of-Function Mutations)

Gene: SDHB hgnc:10681

Autosomal Dominant

Show evidence (1 reference)

PMID:15328326 SUPPORT Human Clinical

"SDHB mutation carriers have an increased frequency of malignant disease (11/32 vs 0/34, P<.001)."

JAMA study demonstrating significantly increased malignancy risk in SDHB mutation carriers compared to SDHD.

SDHD (Germline Loss-of-Function Mutations)

Gene: SDHD hgnc:10683

Autosomal Dominant

Show evidence (1 reference)

PMID:15328326 SUPPORT Human Clinical

"Head and neck paragangliomas (10/32 vs 27/34, respectively, P<.001) and multifocal (9/32 vs 25/34, respectively, P<.001) tumors were more frequent in carriers of SDHD mutations."

JAMA study demonstrating SDHD mutations predispose to head and neck and multifocal paragangliomas.

SDHC (Germline Loss-of-Function Mutations)

Gene: SDHC hgnc:10682

Autosomal Dominant

SDHA (Germline Loss-of-Function Mutations)

Gene: SDHA hgnc:10680

Autosomal Dominant

SDHAF2 (Germline Loss-of-Function Mutations)

Gene: SDHAF2 hgnc:26034

Autosomal Dominant

Show evidence (1 reference)

PMID:19628817 SUPPORT In Vitro

"Sdh5 is required for SDH-dependent respiration and for Sdh1 flavination (incorporation of the flavin adenine dinucleotide cofactor)."

Defines the molecular function of SDHAF2/SDH5 that explains how its loss phenocopies loss of a structural SDH subunit.

MAX (Germline Loss-of-Function Mutations)

Gene: MAX hgnc:6913

Autosomal Dominant

Show evidence (1 reference)

PMID:21685915 SUPPORT Human Clinical

"We sequenced the exomes of three unrelated individuals with hereditary PCC (cases) and identified mutations in MAX, the MYC associated factor X gene."

Original identification of MAX as a hereditary pheochromocytoma gene.

TMEM127 (Germline Loss-of-Function Mutations)

Gene: TMEM127 hgnc:26038

Autosomal Dominant

Show evidence (1 reference)

PMID:20154675 SUPPORT Human Clinical

"In a cohort of 103 samples, we detected truncating germline TMEM127 mutations in approximately 30% of familial tumors and about 3% of sporadic-appearing pheochromocytomas without a known genetic cause."

Quantifies the contribution of TMEM127 to familial and apparently sporadic pheochromocytoma.

FH (Germline Loss-of-Function Mutations)

Gene: FH hgnc:3700

Autosomal Dominant

Show evidence (1 reference)

PMID:24334767 SUPPORT Human Clinical

"Clinically, metastatic phenotype (P = 0.007) and multiple tumors (P = 0.02) were significantly more frequent in patients with FH mutations than those without such mutations."

Establishes the metastatic and multifocal enrichment that justifies including FH in PPGL genetic testing panels.

EPAS1 (Gain-of-Function Variants, Frequently Postzygotic Mosaic)

Gene: EPAS1 hgnc:3374

Show evidence (1 reference)

PMID:22931260 SUPPORT Human Clinical

"The two mutations were associated with increased HIF-2α activity and increased protein half-life."

Demonstrates the gain-of-function mechanism placing EPAS1 in Cluster 1B.

VHL (Germline Loss-of-Function Mutations)

Gene: VHL hgnc:12687

Autosomal Dominant

Show evidence (1 reference)

PMID:32617052 SUPPORT Human Clinical

"In 20% of the patients with VHL, PCC usually occurs and is seen at a young age."

Documents VHL syndrome as a hereditary cause of pheochromocytoma with ~20% penetrance.

RET (Germline Activating Mutations)

Gene: RET hgnc:9967

Autosomal Dominant

Show evidence (1 reference)

PMID:32388798 SUPPORT Human Clinical

"Multiple endocrine neoplasia type 2 (MEN2) is a rare hereditary syndrome due to mutations of the proto-oncogene REarranged during Transfection (RET), defined by the association of medullary thyroid carcinoma (MTC) in almost 100% cases, and pheochromocytoma in roughly 50%"

Review establishing RET mutations in MEN2 cause pheochromocytoma in approximately 50% of patients.

NF1 (Germline Loss-of-Function Mutations)

Gene: NF1 hgnc:7765

Autosomal Dominant

Show evidence (1 reference)

PMID:32617052 SUPPORT Human Clinical

"PPGL develops in 1-5% of patients with NF-1. Almost all of these tumors are PCC, and PGL occurs rarely."

Documents NF1 (neurofibromatosis type 1) as a hereditary cause of PPGL, predominantly pheochromocytoma.

💊

Medical Actions

Surgical Resection

Action: Definitive Surgical Resection NCIT:C154430

Complete surgical resection is the primary treatment for localized PPGL. Requires careful preoperative alpha-blockade followed by beta-blockade to prevent perioperative hypertensive crisis.

Mechanism Target:

INHIBITS Chromaffin Cell Tumorigenesis — Physical removal of the transformed chromaffin-cell mass. This is the only curative intervention in the entry and the only one that acts on the tumor itself rather than on a downstream signalling or secretory consequence.

INHIBITS Catecholamine Hypersecretion — Resection of a functional tumor abolishes the source of catecholamine excess, which is why cure of hypertension is the usual postoperative endpoint.

Show evidence (1 reference)

PMID:24893135 SUPPORT Other

"We recommend minimally invasive adrenalectomy for most pheochromocytomas with open resection for most paragangliomas."

Endocrine Society clinical practice guideline recommending surgical resection as primary treatment.

Alpha-Adrenergic Blockade

Action: Pharmacotherapy NCIT:C15986

Agent: phenoxybenzamine NCIT:C62065 doxazosin CHEBI:4708

Preoperative alpha-blockade with phenoxybenzamine or doxazosin is essential to control hypertension and allow volume expansion before surgery. Beta-blockade must never be started first: unopposed alpha-adrenergic stimulation after beta-blockade can precipitate a hypertensive crisis.

Mechanism Target:

INHIBITS Catecholamine Hypersecretion — Blocks the alpha-adrenergic receptor endpoint of tumor-derived catecholamine excess. This is symptomatic control of the secretory consequence, not antitumor therapy.

Show evidence (1 reference)

PMID:24893135 SUPPORT Other

"All patients with functional PPGLs should undergo preoperative blockade to prevent perioperative complications."

Endocrine Society guideline recommending preoperative alpha blockade for all functional PPGLs.

MIBG Therapy

Action: radiopharmaceutical therapy Ontology label: Radiopharmaceutical Therapy NCIT:C192439

Agent: iobenguane I-131 NCIT:C970

131I-MIBG (metaiodobenzylguanidine) is a targeted radiotherapy for MIBG-avid metastatic PPGL. MIBG is a guanethidine analogue taken up by the noradrenaline transporter, which is what makes it selective for chromaffin tumors; roughly half of metastatic PPGLs are avid enough to be treatable. High-specific-activity 131I-MIBG (iobenguane I-131) is FDA-approved on the strength of a single-arm phase 2 trial in 68 patients whose primary endpoint was a durable halving of antihypertensive requirement - an unusual endpoint chosen because it measures the secretory burden rather than tumor bulk, which is why this treatment is modeled as acting on both the metastatic and the secretory nodes.

Mechanism Target:

INHIBITS Metastatic Progression — Delivers targeted beta radiation to noradrenaline-transporter-expressing metastatic deposits.

INHIBITS Catecholamine Hypersecretion — Reduction of secretory tumor mass lowers circulating catecholamines, which was operationalized as the trial's primary endpoint (durable reduction in antihypertensive medication requirement).

Show evidence (3 references)

PMID:30291194 SUPPORT Human Clinical

"Of the 68 patients who received at least 1 therapeutic dose of HSA 131I-MIBG, 17 (25%; 95% confidence interval, 16%-37%) had a durable reduction in baseline antihypertensive medication use."

Primary endpoint of the registrational phase 2 trial, supporting the secretory-burden target mechanism.

PMID:30291194 SUPPORT Human Clinical

"Among 64 patients with evaluable disease, 59 (92%) had a partial response or stable disease as the best objective response within 12 mo."

Radiographic disease-control result supporting the antitumor target mechanism.

PMID:30291194 SUPPORT Human Clinical

"The median overall survival was 36.7 mo"

Survival outcome in the treated advanced-PPGL population.

Temozolomide

Action: chemotherapy Ontology label: Chemotherapy NCIT:C15632

Agent: temozolomide CHEBI:72564

Alkylating chemotherapy showing activity in metastatic PPGL, particularly SDHB-mutated tumors with MGMT promoter methylation. The SDHB association is mechanistically coherent: the hypermethylator phenotype that makes SDHB tumors aggressive also silences the MGMT repair gene, which is what sensitizes them to an alkylating agent.

Mechanism Target:

INHIBITS Metastatic Progression — Cytotoxic control of metastatic disease, with enhanced activity in the MGMT-silenced, hypermethylated SDHB subgroup. Note that the hypermethylator node is a predictive biomarker here rather than a drug target: SDHB-driven MGMT promoter hypermethylation silences the repair enzyme that would otherwise reverse temozolomide's O6-methylguanine lesions, so no separate target_mechanisms edge is asserted against it.

Show evidence (3 references)

PMID:24752622 SUPPORT Human Clinical

"Median PFS was 13.3 months after a median follow-up of 35 months. There were five partial responses (33%), seven stable (47%) and three progressive diseases (20%)."

Efficacy data from the retrospective series of 15 patients with progressive metastatic PPGL treated with temozolomide.

PMID:24752622 SUPPORT Human Clinical

"Partial responses were observed only in patients with mutation in SDHB."

Establishes the SDHB genotype restriction of response that ties this treatment to the hypermethylator node.

PMID:24752622 SUPPORT Human Clinical

"SDHB germline mutation was associated with hypermethylation of the MGMT promoter and low expression of MGMT in 190 samples of the French nation-wide independent cohort."

Provides the mechanistic link - MGMT silencing by the SDHB hypermethylator phenotype - underpinning the SDHB-restricted response.

Cyclophosphamide-Vincristine-Dacarbazine (CVD) Chemotherapy

Action: chemotherapy Ontology label: Chemotherapy NCIT:C15632

Agent: cyclophosphamide CHEBI:4027 vincristine CHEBI:28445 dacarbazine CHEBI:4305

The conventional cytotoxic backbone for rapidly progressive or high-burden metastatic PPGL, and the comparator against which every newer systemic option is judged. A meta-analysis of four studies (50 patients) found a partial tumor-volume response in about 37% and a partial catecholamine response in about 40%. The authors are explicit that the studies did not define when treatment should start, so part of the apparent benefit may reflect the indolent natural history of PPGL - which is precisely why CVD is reserved for documented progression rather than used on diagnosis of metastatic disease.

Mechanism Target:

INHIBITS Metastatic Progression — Non-targeted cytotoxic control of metastatic tumor burden.

INHIBITS Catecholamine Hypersecretion — Tumor-burden reduction translates into a measurable hormonal response, reported separately from the radiographic response in the meta-analysis.

Show evidence (2 references)

PMID:25041164 SUPPORT Human Clinical

"Data on the effects of a combination of CVD chemotherapy on malignant paraganglioma/pheochromocytoma suggest that a partial response concerning tumour volume can be achieved in about 37% of patients and a partial response on catecholamine excess in about 40% of patients."

Pooled efficacy estimate supporting both the antitumor and the antisecretory target mechanisms.

PMID:25041164 SUPPORT Human Clinical

"Therefore, it cannot be excluded that the reported effect of chemotherapy on tumour volume reflects the natural course of the disease, at least partially."

The authors' own caveat; recorded as PARTIAL because it qualifies rather than establishes the efficacy claim.

Cabozantinib

Action: targeted therapy Ontology label: Targeted Therapy NCIT:C93352

Agent: cabozantinib CHEBI:72317

An antiangiogenic multi-tyrosine-kinase inhibitor (VEGFR2, MET, AXL) with the strongest prospective response data of any systemic agent in metastatic PPGL outside belzutifan. In the single-arm phase 2 Natalie Trial (NCT02302833, 17 patients) the overall response rate was 25%. The rationale is the same pseudohypoxia-driven angiogenic program that motivates sunitinib, and the trial rationale explicitly invokes the SDHB-associated, angiogenesis-high phenotype that dominates hereditary metastatic disease.

Mechanism Target:

INHIBITS Angiogenic and Glycolytic Tumor Program — Blocks VEGFR2-driven neovascularization downstream of the pseudohypoxic HIF program, the same node targeted by sunitinib.

Show evidence (2 references)

PMID:38608693 SUPPORT Human Clinical

"The overall response rate was 25·0% (95% CI 7·3-52·4; four of 16 patients)."

Primary efficacy endpoint of the phase 2 Natalie Trial.

PMID:38608693 SUPPORT Human Clinical

"Up to 50% of MPPGs are associated with germline pathogenic variants of the SDHB gene. These tumours and many non-familial MPPGs exhibit a phenotype that is characterised by abnormal angiogenesis."

States the hereditary-SDHB and angiogenesis rationale that links this drug to the angiogenic-program node.

Sunitinib

Action: targeted therapy Ontology label: Targeted Therapy NCIT:C93352

Agent: sunitinib CHEBI:38940

Multi-kinase inhibitor (VEGFR1-3, PDGFR-alpha/beta, KIT, FLT3, RET) with antiangiogenic activity in progressive metastatic PPGL. No longer prospective-data-poor: FIRSTMAPP, a randomized placebo-controlled phase 2 trial, met its primary endpoint with a 12-month progression-free survival of 36% versus 19% on placebo. Sunitinib also hits RET, so it has a second rationale in the Cluster 2 kinase arm on top of the Cluster 1 antiangiogenic one, though FIRSTMAPP was not powered for a genotype split.

Mechanism Target:

INHIBITS Angiogenic and Glycolytic Tumor Program — Inhibits VEGFR/PDGFR signaling downstream of the pseudohypoxic HIF program, which is the rationale for anti-angiogenic activity being greatest in Cluster 1 tumors.

INHIBITS Kinase Signaling Activation — Sunitinib additionally inhibits RET, giving it a secondary rationale against the Cluster 2 kinase arm; this is a mechanistic inference from the drug's target profile rather than a genotype-stratified trial result.

Show evidence (2 references)

PMID:39735644 SUPPORT Human Clinical

"recently reported that Sunitinib achieved the primary endpoint of 12-month progression-free survival in 36% of patients with progressive metastatic PPGL (90% CI, 23 –50%), compared to 19% in the placebo group (90% CI, 11 –31%)."

FIRSTMAPP, a phase II randomized placebo-controlled trial, is the source of this result; it establishes sunitinib efficacy in progressive metastatic PPGL. The quote begins at 'recently reported' because the preceding words 'placebo- controlled' carry a PDF line-break artifact in the cache, and the en-dashes in the confidence intervals are the cache's own U+2013 characters, reproduced verbatim.

PMID:39735644 SUPPORT Human Clinical

Target profile supporting both the antiangiogenic and the RET/Cluster 2 target mechanisms. (The space inside 'c- kit' is a PDF line-break artifact of the cached full text, reproduced verbatim so the snippet matches; kept on a single quoted line because a folded scalar cannot end a line in a hyphen.)

Belzutifan

Action: targeted therapy Ontology label: Targeted Therapy NCIT:C93352

Agent: belzutifan NCIT:C135627

A HIF-2alpha inhibitor that disrupts the HIF-2alpha/HIF-1beta heterodimer, directly antagonizing the pseudohypoxic node on which every Cluster 1 lesion converges. In the phase 2 LITESPARK-015 trial in advanced PPGL it produced a 26% confirmed objective response rate with 85% disease control and a median progression-free survival of 22.3 months. Notably, a third of participants on antihypertensives were able to halve at least one agent, indicating the drug also reduces the secretory burden and not only tumor bulk. Grade 3 anemia (an on-target consequence of HIF-2-driven erythropoietin suppression) occurred in 22%.

Mechanism Target:

INHIBITS Pseudohypoxia and HIF Activation — Directly inhibits HIF-2alpha, the shared convergence point of Cluster 1A (oncometabolite-mediated PHD inhibition) and Cluster 1B (VHL/EPAS1) lesions. This is the drug-target pattern that makes the pseudohypoxia node clinically actionable.

Show evidence (2 references)

PMID:41124218 SUPPORT Human Clinical

"Most cases of metastatic pheochromocytoma and paraganglioma are driven by dysregulation of the hypoxia-inducible factor 2α (HIF-2α) pathway."

States the mechanistic rationale linking the treatment to the pseudohypoxia pathophysiology node.

PMID:41124218 SUPPORT Human Clinical

"the percentage of participants with disease control was 85% (95% CI, 74 to 92)"

Primary efficacy result of the phase 2 LITESPARK-015 trial supporting belzutifan activity in advanced PPGL.

Peptide Receptor Radionuclide Therapy (177Lu-DOTATATE)

Action: peptide receptor radionuclide therapy Ontology label: Radiopharmaceutical Therapy NCIT:C192439

Agent: Lutetium Lu 177 dotatate NCIT:C95020

Somatostatin-receptor-targeted radionuclide therapy for progressive metastatic PPGL, exploiting the high SSTR2 expression of these tumors that also underlies 68Ga-DOTATATE PET imaging. A phase 2 trial showed a 6-month progression-free survival rate of 0.861 overall, but with a clinically important genotype split: SDHx-mutated patients did significantly worse than apparently sporadic patients. A distinctive hazard is catecholamine release syndrome from radiation-induced tumor lysis, seen at grade 3 or above in 17%, which is why pretreatment alpha-blockade and sometimes planned intensive-care monitoring are used.

Mechanism Target:

INHIBITS Metastatic Progression — Delivers targeted beta radiation to SSTR-expressing metastatic deposits.

Show evidence (2 references)

PMID:40829092 SUPPORT Human Clinical

"Six-month PFS rate for all patients was 0.861 (95% CI, 0.755 to 0.982), which was significantly lower (P = .009) for SDHx at 0.72 (95% CI, 0.542 to 0.962) versus sporadic at 1.00 (95% CI, 1.0 to 1.0)."

Documents both the overall efficacy and the genotype-dependent difference in benefit that is directly relevant to hereditary SDHx disease.

PMID:40829092 SUPPORT Human Clinical

"A 17% incidence of grade 3+ catecholamine release syndrome (CRS) was noted, which may benefit from preemptive ICU admission."

Documents the catecholamine release syndrome hazard specific to treating secretory PPGL with radionuclide therapy.

Genetic Testing and Cascade Screening

Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Germline testing is recommended for all patients with PPGL, not only those with a family history, because roughly 40% carry a germline variant and a substantial minority of apparently sporadic presentations are hereditary. A positive result changes surveillance intensity, informs the site and biochemical phenotype to expect, predicts metastatic risk (SDHB highest), and enables cascade testing of relatives. SDHB immunohistochemistry on resected tumor is a cost-effective way to triage which patients need SDHx sequencing. For SDHD and SDHAF2, the parent-of-origin effect must be explained carefully during counselling.

Show evidence (2 references)

PMID:20301715 SUPPORT Other

"The diagnosis is established in a proband with a personal or family history of paraganglioma or pheochromocytoma and a germline heterozygous pathogenic variant in MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD, or TMEM127 identified by molecular genetic testing."

GeneReviews statement of the molecular diagnostic strategy and the gene panel that defines a hereditary PGL/PCC syndrome.

PMID:20301715 SUPPORT Other

"First-degree relatives of an individual with a hereditary PGL/PCC syndrome and a known MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD, or TMEM127 pathogenic variant should be offered molecular genetic testing to clarify their genetic status"

GeneReviews recommendation underpinning the cascade-testing component of this action.

Lifelong Surveillance for Carriers

Action: surveillance for hereditary PPGL Ontology label: Cancer Screening NCIT:C15406

Asymptomatic pathogenic-variant carriers enter risk-adapted lifelong surveillance, typically combining periodic plasma free metanephrines with whole-body MRI at intervals set by genotype. SDHB carriers receive the most intensive imaging because of their metastatic risk, while SDHD carriers need dedicated head-and-neck coverage for multifocal parasympathetic tumors that may be biochemically silent and therefore invisible to metanephrine testing alone.

Show evidence (3 references)

PMID:20301715 SUPPORT Other

"Individuals at risk for hereditary PGL/PCC syndromes should have annual clinical assessment for manifestations of PGL/PCCs and GISTs, plasma-free fractionated metanephrines or 24-hour urine fractionated metanephrines every two years in childhood and then annually in adults, and whole-body MRI..."

GeneReviews surveillance schedule, the source of the biochemical-plus-MRI protocol described here.

PMID:20301715 SUPPORT Other

"Age of initiation for screening varies by gene."

Supports the genotype-adapted framing of the surveillance schedule rather than a single protocol for all carriers.

PMID:20301715 SUPPORT Other

"approximately 95% of such tumors are nonsecretory"

Quantifies why head-and-neck coverage cannot rely on metanephrine testing - almost all head-and-neck paragangliomas are biochemically silent.

🔬

Biochemical Markers

Plasma Free Normetanephrine

Reference Ranges

Normetanephrine Free [Mass/volume] in Serum or Plasma –0.9 nmol/L (adults, supine sampling)

Normal (–0.9 nmol/L) Equivocal elevation (0.9–2.7 nmol/L) Diagnostic elevation (2.7– nmol/L)

Equivocal elevation: Below roughly three times the upper reference limit. This is the band in which false positives dominate: confirm by repeating supine and drug-free, and consider clonidine suppression before imaging.

Diagnostic elevation: At or above roughly three to four times the upper reference limit, the probability of a PPGL approaches certainty and the workflow moves directly to anatomical and functional localization.

Widely used adult supine upper reference limit; exact cutoffs are assay-, age- and posture-specific and must be taken from the reporting laboratory. Recorded here as an interpretive aid, not as a citable published interval - no primary citation is attached because the value is a laboratory convention rather than a single-study result.

Plasma Free Metanephrine

Reference Ranges

Metanephrine Free [Mass/volume] in Serum or Plasma –0.5 nmol/L (adults, supine sampling)

Conventional adult supine upper reference limit; assay-specific. Recorded as an interpretive aid rather than a citable published interval.

Plasma Free 3-Methoxytyramine

Reference Ranges

3-Methoxytyramine [Moles/volume] in Serum or Plasma –0.1 nmol/L (adults, supine sampling)

Assay-specific upper reference limit, recorded as an interpretive aid. 3-methoxytyramine is particularly sensitive to dietary interference and requires appropriate pre-analytical restriction.

Urinary Catecholamines and Metanephrines

📊

Prevalence

Worldwide

Annual Incidence 0.5 per 100,000 (0.2–0.8) 1–9 per 1,000,000

Reported as 2-8 cases per million per year, normalized here to cases per 100,000.

Show evidence (1 reference)

PMID:32617052 SUPPORT Human Clinical

"The incidence of PCC and PGL ranges between 2 and 8 per million, with a prevalence between 1:2500 and 1:6500."

Source for both the incidence and point-prevalence estimates.

Worldwide

Point Prevalence 25.0 per 100,000 (15.4–40.0) 1–9 per 10,000

Reported as a prevalence between 1:2500 and 1:6500, converted to 40 and 15.4 per 100,000 respectively. Note that figures in this range are frequently quoted for prevalence among hypertensive or clinically selected populations rather than the general population, so this estimate should be treated as an upper bound with uncertain denominator.

Show evidence (1 reference)

PMID:32617052 SUPPORT Human Clinical

"The incidence of PCC and PGL ranges between 2 and 8 per million, with a prevalence between 1:2500 and 1:6500."

Source for the quoted point-prevalence range.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from Pheochromocytoma and Paraganglioma:

Von Hippel-Lindau disease MONDO:0008667

Overlapping Features VHL is itself one of the hereditary PPGL genes (Cluster 1B), so the question is rarely 'PPGL or VHL' but rather whether a PPGL is the presenting feature of VHL disease. VHL-related pheochromocytoma is usually adrenal, often bilateral, noradrenergic, and has low metastatic potential.

Distinguishing Features

Presence of the wider VHL tumor spectrum - retinal and CNS hemangioblastoma, clear cell renal cell carcinoma, pancreatic neuroendocrine tumor, endolymphatic sac tumor.
SDHB immunohistochemistry is retained (positive) in VHL tumors and lost in SDHx tumors, which resolves the distinction on the resection specimen.

Show evidence (1 reference)

PMID:19576851 SUPPORT Human Clinical

Supports SDHB immunohistochemistry as the discriminator between SDHx disease and the VHL/MEN2/NF1 syndromes.

Multiple endocrine neoplasia type 2 MONDO:0019003

Overlapping Features RET-driven MEN2 accounts for a substantial share of hereditary pheochromocytoma. Pheochromocytoma occurs in roughly half of MEN2A patients and most MEN2B patients, and is typically bilateral, adrenal, adrenergic and rarely metastatic.

Distinguishing Features

Medullary thyroid carcinoma (near-universal in MEN2 and usually the presenting tumor), hyperparathyroidism in MEN2A, and the mucosal neuroma/marfanoid habitus of MEN2B.
Biochemically metanephrine-predominant (adrenergic), whereas SDHx disease is normetanephrine-predominant. SDHB staining is retained.

Neurofibromatosis type 1 MONDO:0018975

Overlapping Features NF1 confers a small (roughly 1-5%) lifetime pheochromocytoma risk. Because NF1 is diagnosed clinically it is frequently absent from PPGL gene panels, so the diagnosis rests on recognizing the syndrome rather than on sequencing.

Distinguishing Features

Cafe-au-lait macules, skinfold freckling, cutaneous and plexiform neurofibromas, Lisch nodules, optic pathway glioma.
NF1-related tumors are adrenal and adrenergic, and retain SDHB staining.

Carney-Stratakis syndrome MONDO:0011740

Overlapping Features The dyad of paraganglioma and gastrointestinal stromal tumor caused by germline SDHB, SDHC or SDHD variants. This is not a separate mechanism from hereditary PPGL but a phenotypic presentation of the same SDHx lesion, and the boundary is defined by the presence of GIST.

Distinguishing Features

Co-occurrence of SDH-deficient (KIT/PDGFRA-wildtype, gastric, epithelioid) GIST with paraganglioma in a germline SDHx carrier.
Distinguished from Carney triad, which adds pulmonary chondroma, shows strong female predominance, is usually caused by somatic SDHC promoter hypermethylation rather than a germline variant, and is typically not inherited.

Essential hypertension

Overlapping Features By far the most common alternative explanation for the presenting complaint. PPGL accounts for well under 1% of hypertension in outpatient practice, so the pre-test probability is low and false-positive biochemistry is a real clinical hazard.

Distinguishing Features

Absence of paroxysmal symptoms, normal fractionated metanephrines, and no adrenal or extra-adrenal mass on imaging.
Metanephrine elevations below about three times the upper reference limit are more often explained by posture, stress, or interfering medication (tricyclics, MAO inhibitors, sympathomimetics) than by a tumor.

Panic disorder and anxiety disorders

Overlapping Features Episodic palpitations, sweating, tremor and a sense of impending doom overlap closely with catecholamine paroxysms, and this overlap is a frequent cause of diagnostic delay in both directions.

Distinguishing Features

Panic attacks are typically not accompanied by the marked objective hypertension and pallor of a catecholamine paroxysm; flushing is more typical of anxiety.
Fractionated metanephrines are normal.

Carcinoid syndrome and other neuroendocrine tumors

Overlapping Features Other neuroendocrine tumors can produce episodic vasoactive symptoms and, like PPGL, are somatostatin-receptor-positive on 68Ga-DOTATATE PET, so functional imaging alone does not separate them.

Distinguishing Features

Carcinoid syndrome causes flushing and secretory diarrhea rather than pallor and hypertension.
Associated with elevated urinary 5-HIAA and chromogranin A rather than fractionated metanephrines.

Adrenocortical adenoma or carcinoma

Overlapping Features The commonest competing diagnosis for an incidentally discovered adrenal mass. Distinguishing these before surgery matters, because operating on an unrecognized pheochromocytoma without alpha-blockade risks intraoperative hypertensive crisis.

Distinguishing Features

Adrenocortical lesions are lipid-rich with low unenhanced CT attenuation (10 Hounsfield units or less) and rapid contrast washout, whereas pheochromocytomas are lipid-poor and markedly T2-hyperintense on MRI.
Every adrenal incidentaloma should have metanephrines measured before any planned resection or biopsy.

📊

Related Datasets

Single-nuclei gene-expression analysis of pheochromocytoma and paraganglioma links tumor subtypes with tumor microenvironment ega:EGAS00001005861

Pheochromocytomas and paragangliomas (PCPG) are rare neuroendocrine tumors associated with autonomic nerves. We used single nuclei-RNA-seq (snRNA-seq) for analysis of 30 PCPG representing 13 known driver genes, plus two normal adrenal medullas to dissect cell composition, refine PCPG subtypes and compare PCPG and normal tissue expression. Incorporating bulk-tissue and snRNA-seq data we identified seven PCPG gene-expression subtypes with genotype and cell type associations.

human

European Genome-phenome Archive study, matched because the disease is named in the study's own title ("Pheochromocytoma and Paraganglioma"); description-level mentions were not accepted. EGA study_type: Other. Controlled access -- data require a Data Access Agreement. EGA metadata retrieved 2026-08-01.

Array-based methylation analysis of SDHB-deficient pheochromocytoma and paraganglioma ega:EGAS00001007844

human

European Genome-phenome Archive study, matched because the disease is named in the study's own title ("Pheochromocytoma and Paraganglioma"); description-level mentions were not accepted. EGA study_type: Cancer Genomics. Controlled access -- data require a Data Access Agreement. EGA metadata retrieved 2026-08-01.

Transcriptome analysis of 32 pheochromocytoma and paraganglioma samples ega:EGAS50000000988

Pheochromocytomas and sympathetic paragangliomas (PPGL) are rare neuroendocrine tumors derived from chromaffin tissue of the adrenal medulla and sympathetic paraganglia, respectively. There is at the moment a lack of accurate biomarkers to predict the biologic behavior of a PPGL. The aim of this study was to investigate the biological behavior of localized and metastatic PPGL by comparing the genomic and transcriptomic landscapes of localized and metastatic PPGL, including PPGL samples with a non-metastatic phenotype at initial diagnosis that developed metachronous metastases during follow-up.

human

European Genome-phenome Archive study, matched because the disease is named in the study's own title ("Pheochromocytoma and Paraganglioma"); description-level mentions were not accepted. EGA study_type: RNASeq. Controlled access -- data require a Data Access Agreement. EGA metadata retrieved 2026-08-01.

🔬

Clinical Trials

NCT03206060 PHASE_II RECRUITING

Phase 2 study of 177Lu-DOTATATE (Lutathera) in inoperable or metastatic pheochromocytoma/paraganglioma, with eligibility gated on somatostatin-receptor positivity demonstrated by 68Ga-DOTATATE PET/CT. This is the trial whose interim analysis (PMID:40829092) supplies the efficacy and catecholamine-release-syndrome data recorded on the PRRT treatment, including the SDHx-versus-sporadic progression-free-survival split that makes it directly relevant to the hereditary axis.

Target Phenotypes: Paraganglioma HP:0002668 Pheochromocytoma HP:0002666

Show evidence (1 reference)

clinicaltrials:NCT03206060 SUPPORT Human Clinical

"Adults who have an inoperable tumor of the study cancer that can be detected with Ga-68-DOTATATE PET/CT imaging"

Eligibility criterion confirming the somatostatin-receptor-directed rationale that links this trial to the PRRT treatment entry.

NCT02302833 PHASE_II COMPLETED

The Natalie Trial - single-arm phase 2 study of cabozantinib in unresectable, progressive metastatic pheochromocytoma/paraganglioma. Reported an overall response rate of 25% (PMID:38608693) and is the evidence base for the cabozantinib treatment entry.

Target Phenotypes: Paraganglioma HP:0002668 Pheochromocytoma HP:0002666

Show evidence (1 reference)

clinicaltrials:NCT02302833 SUPPORT Human Clinical

"Cabozantinib s-malate may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth and by blocking the growth of new blood vessels necessary for tumor growth."

Trial summary stating the antiangiogenic mechanism that connects cabozantinib to the Angiogenic and Glycolytic Tumor Program node.

{ }

Source YAML

click to show

name: Pheochromocytoma and Paraganglioma
creation_date: '2026-01-26T02:55:13Z'
description: >-
  Pheochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumors arising
  from chromaffin cells of the adrenal medulla (pheochromocytoma) or extra-adrenal
  sympathetic and parasympathetic ganglia (paraganglioma). Approximately 40% of PPGLs
  are hereditary, caused by germline mutations in over 20 susceptibility genes including
  SDHx subunits (SDHA, SDHB, SDHC, SDHD), VHL, RET, NF1, MAX, and TMEM127. PPGLs may
  be catecholamine-secreting, causing paroxysmal hypertension, headaches, sweating,
  and palpitations. Understanding the genetic basis has enabled surveillance, early
  detection, and emerging targeted therapies for this heterogeneous tumor group.

  This entry covers both the sporadic tumor entity (MONDO:0035540) and the hereditary
  pheochromocytoma-paraganglioma predisposition syndrome (MONDO:0017366), which is
  modeled here as the genetic-locus axis of `has_subtypes` (PGL1-PGL5 plus the MAX-
  and TMEM127-related forms) rather than as a separate Disease entry. Hereditary PPGL
  is mechanistically split into two transcriptional clusters: Cluster 1 (pseudohypoxic)
  comprising Cluster 1A (SDHx, FH - oncometabolite-driven) and Cluster 1B (VHL, EPAS1
  - direct HIF-axis lesions), and Cluster 2 (kinase-signaling; RET, NF1, TMEM127, MAX).
  This cluster assignment predicts the secretory phenotype, the tumor location, and the
  metastatic risk that drive clinical surveillance.
categories:
- Neuroendocrine Tumor
- Hereditary Cancer Syndrome
- Adrenal Tumor
parents:
- neuroendocrine tumor
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0017366
      label: hereditary pheochromocytoma-paraganglioma
    mapping_predicate: skos:closeMatch
    mapping_source: MONDO
    notes: >-
      The hereditary predisposition-syndrome sibling term. MONDO models the tumor
      entity (MONDO:0035540, this entry's disease_term) and the hereditary syndrome
      (MONDO:0017366) on separate branches; per curation decision on issue #7475 the
      hereditary axis is curated here as genetic-locus subtypes rather than as a
      duplicate Disease entry.
has_subtypes:
- name: Pheochromocytoma
  description: >-
    Tumors arising from the adrenal medulla chromaffin cells. Most common site
    of catecholamine-producing paraganglioma. Usually unilateral but bilateral
    in hereditary syndromes.
- name: Sympathetic Paraganglioma
  description: >-
    Extra-adrenal tumors arising from sympathetic ganglia along the paravertebral
    axis (thorax, abdomen, pelvis). Often catecholamine-secreting. SDHB mutations
    associated with high malignancy risk.
- name: Parasympathetic Paraganglioma
  description: >-
    Head and neck paragangliomas arising from parasympathetic ganglia (carotid
    body, jugulotympanic, vagal). Usually non-secreting. SDHD mutations common.
- name: PGL1
  display_name: PGL1 - SDHD-related hereditary paraganglioma-pheochromocytoma
  description: >-
    SDHD (11q23) germline loss of function. The most penetrant head-and-neck
    paraganglioma locus, typically multifocal and frequently non-secretory.
    Disease is expressed almost exclusively after paternal transmission (see the
    inheritance section); the operative somatic event is loss of the entire
    maternal chromosome 11 rather than classical two-hit loss of the SDHD locus
    alone. Metastatic risk is substantially lower than for SDHB/PGL4.
  subtype_term:
    preferred_term: pheochromocytoma/paraganglioma syndrome 1
    term:
      id: MONDO:0008192
      label: pheochromocytoma/paraganglioma syndrome 1
  genes:
  - preferred_term: SDHD
    term:
      id: hgnc:10683
      label: SDHD
  inheritance:
  - name: Autosomal dominant with maternal imprinting
    inheritance_term:
      preferred_term: Autosomal dominant inheritance with maternal imprinting
      term:
        id: HP:0012275
        label: Autosomal dominant inheritance with maternal imprinting
    penetrance: INCOMPLETE
    penetrance_percentage: 43.2% by age 60 (paternally inherited, non-probands)
    parent_of_origin_effect: Paternal transmission required for expression
    evidence:
    - reference: PMID:29386252
      reference_title: Tumour risks and genotype-phenotype correlations associated with germline variants in succinate dehydrogenase subunit genes SDHB, SDHC and SDHD.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        By Kaplan-Meier analysis, the penetrance (cumulative risk of clinically
        apparent tumours) in SDHB and (paternally inherited) SDHD
        mutation-positive non-probands (n=371/67 with detailed clinical
        information) by age 60 years was 21.8% (95% CI 15.2% to 27.9%) and 43.2%
        (95% CI 25.4% to 56.7%), respectively.
      explanation: >-
        Source of the 43.2%-by-60 paternally inherited SDHD penetrance estimate,
        computed in non-probands to limit ascertainment bias.
  evidence:
  - reference: PMID:15064708
    reference_title: "Somatic loss of maternal chromosome 11 causes parent-of-origin-dependent inheritance in SDHD-linked paraganglioma and phaeochromocytoma families."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In SDHD (11q23)-linked families, the disease phenotype is expressed only
      upon paternal transmission of the mutation, consistent with maternal
      imprinting.
    explanation: >-
      Establishes the SDHD locus assignment (11q23) and the parent-of-origin
      expression pattern that defines PGL1.
- name: PGL2
  display_name: PGL2 - SDHAF2-related hereditary paraganglioma
  description: >-
    SDHAF2 (also called SDH5, 11q13) germline loss of function. SDHAF2 is an
    assembly factor required for flavination of the SDHA catalytic subunit, so
    its loss disables the SDH complex without mutating a structural subunit. The
    rarest of the PGL loci; presents essentially as multifocal head-and-neck
    paraganglioma, and like PGL1 shows parent-of-origin (paternal transmission)
    expression. Pheochromocytoma is uncommon in this subtype.
  subtype_term:
    preferred_term: pheochromocytoma/paraganglioma syndrome 2
    term:
      id: MONDO:0011121
      label: pheochromocytoma/paraganglioma syndrome 2
  genes:
  - preferred_term: SDHAF2
    term:
      id: hgnc:26034
      label: SDHAF2
  inheritance:
  - name: Autosomal dominant with maternal imprinting
    inheritance_term:
      preferred_term: Autosomal dominant inheritance with maternal imprinting
      term:
        id: HP:0012275
        label: Autosomal dominant inheritance with maternal imprinting
  evidence:
  - reference: PMID:19628817
    reference_title: "SDH5, a gene required for flavination of succinate dehydrogenase, is mutated in paraganglioma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Germline loss-of-function mutations in the human SDH5 gene, located on
      chromosome 11q13.1, segregate with disease in a family with hereditary
      paraganglioma, a neuroendocrine tumor previously linked to mutations in
      genes encoding SDH subunits.
    explanation: >-
      Original identification of SDHAF2/SDH5 as the PGL2 gene, including the
      11q13.1 locus assignment.
- name: PGL3
  display_name: PGL3 - SDHC-related hereditary paraganglioma-pheochromocytoma
  description: >-
    SDHC (1q23) germline loss of function. Predominantly head-and-neck
    paraganglioma, usually unifocal, with comparatively low metastatic risk.
    Standard (non-imprinted) autosomal dominant transmission. SDHC promoter
    hypermethylation - rather than germline mutation - is the usual lesion in
    Carney triad, which is a distinct entity.
  subtype_term:
    preferred_term: pheochromocytoma/paraganglioma syndrome 3
    term:
      id: MONDO:0011544
      label: pheochromocytoma/paraganglioma syndrome 3
  genes:
  - preferred_term: SDHC
    term:
      id: hgnc:10682
      label: SDHC
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
- name: PGL4
  display_name: PGL4 - SDHB-related hereditary paraganglioma-pheochromocytoma
  description: >-
    SDHB (1p36) germline loss of function. The clinically most consequential
    locus: extra-adrenal sympathetic (abdominal/thoracic) paraganglioma
    predominates, and SDHB carries by far the highest risk of metastatic disease
    of any PPGL susceptibility gene, which is why it drives the most intensive
    lifelong surveillance. Epigenetic silencing is most severe in SDHB-mutated
    tumors, offering a mechanistic explanation for that malignancy. Standard
    (non-imprinted) autosomal dominant transmission. Also confers risk of renal
    cell carcinoma and gastrointestinal stromal tumor.
  subtype_term:
    preferred_term: pheochromocytoma/paraganglioma syndrome 4
    term:
      id: MONDO:0007273
      label: pheochromocytoma/paraganglioma syndrome 4
  genes:
  - preferred_term: SDHB
    term:
      id: hgnc:10681
      label: SDHB
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    penetrance: INCOMPLETE
    penetrance_percentage: 23.9% by age 60 and 30.6% by age 80 (ascertainment-adjusted)
    evidence:
    - reference: PMID:29386252
      reference_title: Tumour risks and genotype-phenotype correlations associated with germline variants in succinate dehydrogenase subunit genes SDHB, SDHC and SDHD.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        With retrospective cohort analysis to adjust for ascertainment, cumulative
        tumour risks for SDHB mutation carriers at ages 60 years and 80 years were
        23.9% (95% CI 20.9% to 27.4%) and 30.6% (95% CI 26.8% to 34.7%).
      explanation: >-
        Source of the ascertainment-adjusted SDHB penetrance estimates; markedly
        lower than the historical clinically ascertained figures.
    - reference: PMID:29386252
      reference_title: Tumour risks and genotype-phenotype correlations associated with germline variants in succinate dehydrogenase subunit genes SDHB, SDHC and SDHD.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Risk of malignant disease at age 60 years in non-proband SDHB mutation
        carriers was 4.2%(95% CI 1.1% to 7.2%).
      explanation: >-
        Quantifies the absolute metastatic risk that drives the intensive SDHB
        surveillance schedule - high relative to other loci but low in absolute terms.
  evidence:
  - reference: PMID:15328326
    reference_title: "Distinct clinical features of paraganglioma syndromes associated with SDHB and SDHD gene mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SDHB mutation carriers have an increased frequency of malignant disease (11/32 vs 0/34, P<.001)."
    explanation: >-
      Direct comparison establishing the elevated metastatic risk of SDHB
      carriers relative to SDHD carriers.
- name: PGL5
  display_name: PGL5 - SDHA-related hereditary paraganglioma-pheochromocytoma
  description: >-
    SDHA (5p15) germline loss of function. SDHA encodes the flavoprotein
    catalytic subunit of complex II. Low-penetrance PPGL predisposition with a
    broad tumor spectrum including gastrointestinal stromal tumor. Biallelic
    (recessive) SDHA loss causes a mechanistically distinct, non-neoplastic
    disease - mitochondrial complex II deficiency with Leigh syndrome - which is
    curated separately and is not part of this tumor-predisposition subtype.
  subtype_term:
    preferred_term: pheochromocytoma/paraganglioma syndrome 5
    term:
      id: MONDO:0013602
      label: pheochromocytoma/paraganglioma syndrome 5
  genes:
  - preferred_term: SDHA
    term:
      id: hgnc:10680
      label: SDHA
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
- name: MAX-related
  display_name: MAX-related tumor predisposition
  description: >-
    MAX (14q23) germline loss of function. A Cluster 2 (kinase-signaling/MYC
    network) rather than pseudohypoxic subtype: MAX is the obligate dimerization
    partner of MYC, and its loss deregulates the MYC-MAX-MXD1 network. Typically
    bilateral adrenal pheochromocytoma with a noradrenergic secretory profile,
    and an appreciable metastatic rate. Preferential paternal transmission has
    been reported, though this is a weaker and less well-established effect than
    the SDHD/SDHAF2 parent-of-origin phenomenon.
  subtype_term:
    preferred_term: MAX-related tumor predisposition
    term:
      id: MONDO:0700346
      label: MAX-related tumor predisposition
  genes:
  - preferred_term: MAX
    term:
      id: hgnc:6913
      label: MAX
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:21685915
    reference_title: "Exome sequencing identifies MAX mutations as a cause of hereditary pheochromocytoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A follow-up study of a selected series of 59 cases with PCC identified
      five additional MAX mutations and suggested an association with malignant
      outcome and preferential paternal transmission of MAX mutations.
    explanation: >-
      Identifies MAX as a hereditary pheochromocytoma gene and reports both the
      malignant-outcome association and the preferential paternal transmission
      (stated by the authors as a suggestion, not an established rule).
- name: TMEM127-related
  display_name: TMEM127-related tumor predisposition
  description: >-
    TMEM127 (2q11) germline loss of function. A Cluster 2 kinase-signaling
    subtype: TMEM127 is a negative regulator of mTOR, and TMEM127-mutant tumors
    are transcriptionally akin to NF1-mutant tumors and show hyperphosphorylation
    of mTOR effectors. Usually adrenal, frequently bilateral pheochromocytoma
    with an adrenergic secretory profile and a low metastatic rate. Also confers
    renal cell carcinoma risk.
  subtype_term:
    preferred_term: TMEM127-related tumor predisposition
    term:
      id: MONDO:0700345
      label: TMEM127-related tumor predisposition
  genes:
  - preferred_term: TMEM127
    term:
      id: hgnc:26038
      label: TMEM127
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:20154675
    reference_title: "Germline mutations in TMEM127 confer susceptibility to pheochromocytoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pheochromocytomas with mutations in TMEM127 are transcriptionally related
      to tumors bearing NF1 mutations and, similarly, show hyperphosphorylation
      of mammalian target of rapamycin (mTOR) effector proteins.
    explanation: >-
      Establishes TMEM127 as a PPGL susceptibility gene acting through mTOR,
      placing it in the kinase-signaling (Cluster 2) group alongside NF1.
prevalence:
- population: Worldwide
  measure_type: ANNUAL_INCIDENCE
  prevalence_class: BAND_1_9_PER_1000000
  rate_per_100000: 0.5
  rate_low: 0.2
  rate_high: 0.8
  notes: >-
    Reported as 2-8 cases per million per year, normalized here to cases per
    100,000.
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The incidence of PCC and PGL ranges between 2 and 8 per million, with a
      prevalence between 1:2500 and 1:6500.
    explanation: Source for both the incidence and point-prevalence estimates.
- population: Worldwide
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 25.0
  rate_low: 15.4
  rate_high: 40.0
  notes: >-
    Reported as a prevalence between 1:2500 and 1:6500, converted to 40 and 15.4
    per 100,000 respectively. Note that figures in this range are frequently
    quoted for prevalence among hypertensive or clinically selected populations
    rather than the general population, so this estimate should be treated as
    an upper bound with uncertain denominator.
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The incidence of PCC and PGL ranges between 2 and 8 per million, with a
      prevalence between 1:2500 and 1:6500.
    explanation: Source for the quoted point-prevalence range.
pathophysiology:
- name: Succinate Dehydrogenase Complex Dysfunction
  conforms_to: "oncometabolite_dioxygenase_inhibition#Metabolic Enzyme Lesion (TCA Tumor Suppressor Loss or IDH Neomorphic Gain)"
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    Mutations in SDHx genes (SDHA, SDHB, SDHC, SDHD, SDHAF2) impair mitochondrial
    complex II function, leading to succinate accumulation. Succinate acts as an
    oncometabolite, inhibiting alpha-ketoglutarate-dependent dioxygenases and
    causing pseudohypoxia and epigenetic dysregulation.
  evidence:
  - reference: PMID:33112834
    reference_title: "Epigenetic and metabolic reprogramming of SDH-deficient paragangliomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SDHx mutations lead to the accumulation of succinate, which acts as an oncometabolite by inhibiting iron(II) and alpha-ketoglutarate-dependent dioxygenases thereby regulating the cell's hypoxic response and epigenetic processes."
    explanation: This abstract connects SDHx mutations to succinate accumulation and dioxygenase inhibition, matching the described mechanism.
  cell_types:
  - preferred_term: chromaffin cell
    term:
      id: CL:0000166
      label: chromaffin cell
  molecular_functions:
  - preferred_term: succinate dehydrogenase activity
    modifier: DECREASED
    term:
      id: GO:0000104
      label: succinate dehydrogenase activity
  locations:
  - preferred_term: adrenal gland
    term:
      id: UBERON:0002369
      label: adrenal gland
  downstream:
  - target: Succinate Accumulation and Oncometabolite Signaling
    description: >-
      Loss of complex II catalytic activity blocks oxidation of succinate to
      fumarate, so succinate accumulates to millimolar concentrations.
- name: Succinate Accumulation and Oncometabolite Signaling
  conforms_to: "oncometabolite_dioxygenase_inhibition#Competitive Inhibition of 2-Oxoglutarate-Dependent Dioxygenases"
  biological_scale: MOLECULAR
  role: central_effector
  description: >-
    Succinate accumulating behind the complex II block acts as an oncometabolite.
    Because succinate is a structural analog of 2-oxoglutarate (alpha-ketoglutarate),
    it competitively inhibits the large family of 2-oxoglutarate-dependent
    dioxygenases. This single biochemical event is the branch point from which both
    arms of Cluster 1A pathology derive: inhibition of the TET DNA
    5-methylcytosine dioxygenases and JmjC histone demethylases produces the
    hypermethylator phenotype, while inhibition of the HIF prolyl hydroxylases
    (PHDs) produces pseudohypoxia. The same logic applies to fumarate in
    FH-mutant tumors, which display an 'SDH-like' epigenetic phenotype.
  molecular_functions:
  - preferred_term: 2-oxoglutarate-dependent dioxygenase activity
    modifier: DECREASED
    term:
      id: GO:0016706
      label: 2-oxoglutarate-dependent dioxygenase activity
  cell_types:
  - preferred_term: chromaffin cell
    term:
      id: CL:0000166
      label: chromaffin cell
  evidence:
  - reference: PMID:33112834
    reference_title: "Epigenetic and metabolic reprogramming of SDH-deficient paragangliomas."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "SDHx mutations lead to the accumulation of succinate, which acts as an oncometabolite by inhibiting iron(II) and alpha-ketoglutarate-dependent dioxygenases thereby regulating the cell's hypoxic response and epigenetic processes."
    explanation: >-
      States the competitive-inhibition mechanism and that it drives both the
      hypoxic-response and epigenetic arms.
  downstream:
  - target: DNA and Histone Hypermethylator Phenotype
    description: >-
      Inhibition of TET dioxygenases and JmjC histone demethylases blocks
      demethylation, producing genome-wide hypermethylation.
  - target: Pseudohypoxia and HIF Activation
    description: >-
      Inhibition of HIF prolyl hydroxylases prevents HIF-alpha hydroxylation and
      VHL-mediated degradation.
- name: DNA and Histone Hypermethylator Phenotype
  conforms_to: "oncometabolite_dioxygenase_inhibition#Impaired Demethylation and Genome-Wide Hypermethylation"
  biological_scale: MOLECULAR
  role: effector
  description: >-
    SDHx-mutant paragangliomas form a distinct methylome cluster characterized by
    genome-wide DNA and histone hypermethylation (a CpG island methylator
    phenotype). Succinate-driven inhibition of 2-oxoglutarate-dependent TET and
    JmjC demethylases silences genes governing neuroendocrine differentiation and
    establishes a migratory phenotype. Epigenetic silencing is most severe in
    SDHB-mutant tumors, which provides the leading mechanistic explanation for why
    SDHB carries the highest metastatic risk. The phenotype is pharmacologically
    reversible with a demethylating agent in model systems.
  biological_processes:
  - preferred_term: epigenetic regulation of gene expression
    modifier: ABNORMAL
    term:
      id: GO:0040029
      label: epigenetic regulation of gene expression
  molecular_functions:
  - preferred_term: DNA 5-methylcytosine dioxygenase activity
    modifier: DECREASED
    term:
      id: GO:0070579
      label: DNA 5-methylcytosine dioxygenase activity
  - preferred_term: histone demethylase activity
    modifier: DECREASED
    term:
      id: GO:0032452
      label: histone demethylase activity
  evidence:
  - reference: PMID:23707781
    reference_title: "SDH mutations establish a hypermethylator phenotype in paraganglioma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Succinate accumulation in SDH-deficient mouse chromaffin cells led to DNA
      hypermethylation by inhibition of 2-OG-dependent histone and DNA
      demethylases and established a migratory phenotype reversed by decitabine
      treatment.
    explanation: >-
      Direct experimental demonstration that succinate inhibits 2-OG-dependent
      demethylases and produces the hypermethylator/migratory phenotype.
  - reference: PMID:23707781
    reference_title: "SDH mutations establish a hypermethylator phenotype in paraganglioma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Epigenetic silencing was particularly severe in SDHB-mutated tumors,
      potentially explaining their malignancy.
    explanation: >-
      Links severity of the hypermethylator phenotype specifically to SDHB and to
      metastatic behavior.
  downstream:
  - target: Metastatic Progression
    description: >-
      Hypermethylation-driven silencing of differentiation genes and acquisition
      of a migratory phenotype, most marked in SDHB-mutant tumors.
  - target: Noradrenergic and Dopaminergic Secretory Phenotype
    description: >-
      Downregulation of neuroendocrine differentiation genes, including the
      PNMT-dependent maturation required for epinephrine synthesis.
- name: Pseudohypoxia and HIF Activation
  biological_scale: CELLULAR
  role: central_effector
  conforms_to: "oncometabolite_dioxygenase_inhibition#Pseudohypoxic HIF Stabilization"
  description: >-
    Constitutive stabilization of hypoxia-inducible factors (chiefly HIF-2alpha)
    under normoxic conditions - a 'pseudohypoxic' state. Cluster 1A reaches it by
    oncometabolite inhibition of the prolyl hydroxylases; Cluster 1B reaches the
    same node directly, either by loss of the VHL E3 ligase that recognizes
    hydroxylated HIF-alpha, or by gain-of-function EPAS1/HIF2A variants that
    escape hydroxylation. The convergence of these distinct lesions on one node is
    what makes HIF-2alpha a shared druggable target across Cluster 1.
  biological_processes:
  - preferred_term: response to hypoxia
    modifier: INCREASED
    term:
      id: GO:0001666
      label: response to hypoxia
  - preferred_term: peptidyl-proline hydroxylation to 4-hydroxy-L-proline
    modifier: DECREASED
    term:
      id: GO:0018401
      label: peptidyl-proline hydroxylation to 4-hydroxy-L-proline
  evidence:
  - reference: PMID:15652751
    reference_title: "Succinate links TCA cycle dysfunction to oncogenesis by inhibiting HIF-alpha prolyl hydroxylase."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      succinate, which accumulates as a result of SDH inhibition, inhibits
      HIF-alpha prolyl hydroxylases in the cytosol, leading to stabilization and
      activation of HIF-1alpha.
    explanation: >-
      The foundational demonstration that succinate inhibits the PHDs, defining
      the pseudohypoxia mechanism.
  - reference: PMID:22931260
    reference_title: "Somatic HIF2A gain-of-function mutations in paraganglioma with polycythemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we report two novel somatic gain-of-function mutations in the gene
      encoding hypoxia-inducible factor 2α (HIF2A) in two patients, one presenting
      with paraganglioma and the other with paraganglioma and somatostatinoma,
      both of whom had polycythemia.
    explanation: >-
      Establishes the Cluster 1B EPAS1/HIF2A route to the same pseudohypoxic node,
      with the polycythemia that distinguishes it clinically.
  downstream:
  - target: Angiogenic and Glycolytic Tumor Program
    description: >-
      Stabilized HIF drives transcription of VEGF and glycolytic enzyme genes.
- name: Angiogenic and Glycolytic Tumor Program
  biological_scale: CELLULAR
  role: effector
  conforms_to: "tumor_angiogenesis#Angiogenic Switch and VEGF-Driven Neovascularization"
  description: >-
    HIF-driven transcription of VEGF, PDGF, EPO and glycolytic enzymes produces the
    characteristically hypervascular PPGL and a glycolytic metabolic shift. This
    node is the rationale for both anti-angiogenic multikinase inhibitors and for
    18F-FDG PET avidity, which is highest in SDHx-related disease.
  biological_processes:
  - preferred_term: angiogenesis
    modifier: INCREASED
    term:
      id: GO:0001525
      label: angiogenesis
  - preferred_term: glycolytic process
    modifier: INCREASED
    term:
      id: GO:0006096
      label: glycolytic process
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the pseudohypoxic tumor environment stimulates VEGF synthesis, promoting
      angiogene sis
    explanation: >-
      States the pseudohypoxia-to-VEGF-to-angiogenesis link that defines this
      node and its tumor_angiogenesis conformance. (The space inside
      'angiogene sis' is a PDF line-break artifact of the cached full text and
      is reproduced verbatim so the snippet matches the cache.)
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sunitinib, which inhibits VEGF1, VEGF2, VEGF3, PDGF-alpha, PDGF-beta, c- kit, fms-related tyrosine kinase 3, and RET proto-oncogene receptors, has demonstrated potential in reducing angiogenesis and tumor cell growth."
    explanation: >-
      Confirms this node is the actionable target of the antiangiogenic
      multikinase inhibitors that declare target_mechanisms against it. (The
      space inside 'c- kit' is a PDF line-break artifact of the cached full
      text, reproduced verbatim.)
  downstream:
  - target: Chromaffin Cell Tumorigenesis
    description: >-
      Sustained angiogenic and metabolic support permits expansion of the
      neoplastic chromaffin-cell clone.
- name: Kinase Signaling Activation
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    The Cluster 2 arm, mechanistically distinct from pseudohypoxia. RET
    gain-of-function (MEN2), NF1 loss (neurofibromin is a RAS GTPase-activating
    protein), TMEM127 loss (a negative regulator of mTOR) and MAX loss (the
    obligate MYC dimerization partner) converge on RAS-MAPK and PI3K-AKT-mTOR
    signaling. Cluster 2 tumors are typically adrenal, well-differentiated, and
    adrenergic-secreting, with a low metastatic rate - the clinical mirror image
    of SDHB disease.
  molecular_functions:
  - preferred_term: protein tyrosine kinase activity
    modifier: INCREASED
    term:
      id: GO:0004713
      label: protein tyrosine kinase activity
  biological_processes:
  - preferred_term: TOR signaling
    modifier: INCREASED
    term:
      id: GO:0031929
      label: TOR signaling
  evidence:
  - reference: PMID:20154675
    reference_title: "Germline mutations in TMEM127 confer susceptibility to pheochromocytoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Accordingly, in vitro gain-of-function and loss-of-function analyses
      indicate that TMEM127 is a negative regulator of mTOR.
    explanation: >-
      Establishes the mTOR axis as the mechanism of the TMEM127 Cluster 2 subtype.
  downstream:
  - target: Chromaffin Cell Tumorigenesis
    description: >-
      Constitutive mitogenic signaling drives chromaffin-cell proliferation and
      survival.
  - target: Adrenergic Secretory Phenotype
    description: >-
      Cluster 2 tumors retain a mature adrenal chromaffin phenotype with PNMT
      expression, so they synthesize epinephrine.
- name: Somatic Loss of Maternal Chromosome 11
  conforms_to: "germline_two_hit_tumor_predisposition#Somatic Second-Hit Inactivation of the Wild-Type Allele"
  biological_scale: CELLULAR
  role: mediator
  description: >-
    The mechanistic explanation for the SDHD/SDHAF2 parent-of-origin effect. Both
    genes lie on chromosome 11 (SDHD at 11q23, SDHAF2 at 11q13). Tumorigenesis
    requires loss of the wild-type maternal allele, and in SDHD-linked tumors the
    event is loss of the entire maternal chromosome 11 rather than a focal second
    hit. Because that single event must remove the wild-type copy, a mutation
    inherited from the mother is not usually unmasked, and disease is expressed
    almost exclusively after paternal transmission. Note that this is not simple
    classical imprinting: SDHD shows biallelic expression in several normal
    tissues, and the loss of the co-deleted imprinted 11p15 region is thought to
    contribute.
  locations:
  - preferred_term: adrenal medulla
    term:
      id: UBERON:0001236
      label: adrenal medulla
  evidence:
  - reference: PMID:15064708
    reference_title: "Somatic loss of maternal chromosome 11 causes parent-of-origin-dependent inheritance in SDHD-linked paraganglioma and phaeochromocytoma families."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we demonstrate exclusive loss of the entire maternal chromosome 11 in
      SDHD-linked paragangliomas and phaeochromocytomas
    explanation: >-
      Direct demonstration of the somatic event underlying the parent-of-origin
      pattern in SDHD-linked disease.
  downstream:
  - target: Succinate Dehydrogenase Complex Dysfunction
    description: >-
      Loss of the wild-type maternal allele completes biallelic SDHD inactivation
      in the tumor precursor cell.
- name: Chromaffin Cell Tumorigenesis
  biological_scale: TISSUE
  role: consequence
  description: >-
    Clonal expansion of neoplastic chromaffin or glomus cells to form a
    pheochromocytoma (adrenal medulla) or paraganglioma (extra-adrenal sympathetic
    chain, or parasympathetic head-and-neck paraganglia). Genotype largely
    predicts site: SDHB favors extra-adrenal abdominal/thoracic sympathetic
    tumors, SDHD and SDHAF2 favor multifocal head-and-neck parasympathetic tumors,
    and Cluster 2 genes favor bilateral adrenal pheochromocytoma.
  cell_types:
  - preferred_term: chromaffin cell
    term:
      id: CL:0000166
      label: chromaffin cell
  locations:
  - preferred_term: adrenal medulla
    term:
      id: UBERON:0001236
      label: adrenal medulla
  - preferred_term: carotid body
    term:
      id: UBERON:0001629
      label: carotid body
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pheochromocytomas arise from chromaffin cells in the adrenal medulla, and
      PGLs arise from chromaffin cells in the ganglia of the autonomic nervous
      system.
    explanation: >-
      Establishes the chromaffin-cell origin and the adrenal-versus-extra-adrenal
      site split that this node models.
  - reference: PMID:15328326
    reference_title: "Distinct clinical features of paraganglioma syndromes associated with SDHB and SDHD gene mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Head and neck paragangliomas (10/32 vs 27/34, respectively, P<.001) and multifocal (9/32 vs 25/34, respectively, P<.001) tumors were more frequent in carriers of SDHD mutations."
    explanation: >-
      Supports the genotype-predicts-site claim, contrasting SDHD head-and-neck
      multifocal disease with the SDHB extra-adrenal pattern.
  downstream:
  - target: Catecholamine Hypersecretion
    description: >-
      Secretory tumors release catecholamines into the circulation independently
      of neural control.
  - target: Metastatic Progression
    description: >-
      A subset progresses to metastatic disease, defined by tumor at sites where
      chromaffin tissue is not normally present.
- name: Noradrenergic and Dopaminergic Secretory Phenotype
  biological_scale: CELLULAR
  role: effector
  description: >-
    SDHx-related and other Cluster 1 tumors, and parasympathetic head-and-neck
    paragangliomas, lack or downregulate phenylethanolamine N-methyltransferase
    (PNMT), the cortisol-dependent enzyme that converts norepinephrine to
    epinephrine and which requires the adrenal cortical microenvironment. They
    therefore secrete norepinephrine (measured as normetanephrine) and sometimes
    dopamine (measured as 3-methoxytyramine) rather than epinephrine. Many
    head-and-neck parasympathetic paragangliomas are biochemically silent
    altogether and present as a painless neck mass or with cranial-nerve palsy,
    not with catecholamine symptoms - which is precisely why a normal metanephrine
    panel cannot exclude them.
  biological_processes:
  - preferred_term: catecholamine biosynthetic process
    modifier: ABNORMAL
    term:
      id: GO:0042423
      label: catecholamine biosynthetic process
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Almost all tumors with mutations in cluster 1 are tumors with a
      noradrenergic biochemical phenotype. These produce norepinephrine and
      dopamine, not epinephrine.
    explanation: >-
      Establishes the Cluster 1 noradrenergic/dopaminergic secretory phenotype
      that defines this node.
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PGLs, on the other hand, are not able to synthesize epinephrine since they
      do not contain the PNMT enzyme. They only secrete norepinephrine.
    explanation: >-
      Gives the PNMT-absence mechanism underlying the noradrenergic profile of
      extra-adrenal paraganglioma.
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, approximately 2/3 of PGLs of parasympathetic origin in the head
      and neck region are not endocrine active.
    explanation: >-
      Supports the biochemically silent head-and-neck presentation and hence the
      statement that a normal metanephrine panel cannot exclude these tumors.
  downstream:
  - target: Catecholamine Hypersecretion
    description: >-
      Where the tumor is secretory, the released amine is predominantly
      norepinephrine and/or dopamine.
- name: Adrenergic Secretory Phenotype
  biological_scale: CELLULAR
  role: effector
  description: >-
    Cluster 2 (RET/NF1/TMEM127) and other adrenal tumors retain PNMT expression
    and secrete epinephrine, measured as metanephrine. The adrenergic versus
    noradrenergic split is the basis on which a fractionated metanephrine panel
    becomes genotype-informative rather than merely diagnostic: a
    metanephrine-predominant pattern points toward RET/NF1, a
    normetanephrine-predominant pattern toward VHL/SDHx, and a
    3-methoxytyramine elevation toward SDHx and dopaminergic, often metastatic,
    disease.
  biological_processes:
  - preferred_term: catecholamine biosynthetic process
    modifier: INCREASED
    term:
      id: GO:0042423
      label: catecholamine biosynthetic process
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Many of the cluster 2 mutations have adrenergic biochemical phenotype and
      are associated with increased epinephrine production as a result of high
      PNMT expression.
    explanation: >-
      Establishes the Cluster 2 adrenergic secretory phenotype and its PNMT
      basis, the mirror image of the Cluster 1 node.
  downstream:
  - target: Catecholamine Hypersecretion
    description: Epinephrine release drives the classic paroxysmal symptom triad.
- name: Catecholamine Hypersecretion
  biological_scale: ORGANISM
  role: outcome
  description: >-
    Secreting PPGLs produce excess catecholamines (norepinephrine, epinephrine,
    dopamine), causing characteristic symptoms. The catecholamine profile provides
    clues to underlying genetics: norepinephrine-predominant suggests SDHx/VHL,
    epinephrine-predominant suggests RET/NF1.
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The majority of PCC and sympathetic PGL are endocrine active tumors causing clinical symptoms by secreting excess catecholamines (norepinephrine, epinephrine, dopamine) and their metabolites."
    explanation: "Abstract notes catecholamine-secreting tumors causing clinical symptoms."
  biological_processes:
  - preferred_term: catecholamine biosynthetic process
    modifier: INCREASED
    term:
      id: GO:0042423
      label: catecholamine biosynthetic process
- name: Metastatic Progression
  biological_scale: ORGANISM
  role: outcome
  description: >-
    Metastatic PPGL is defined by the presence of tumor at sites where chromaffin
    tissue is not normally found (bone, liver, lung, lymph node) - the WHO 2022
    endocrine classification retired the benign/malignant dichotomy because all
    PPGL carry some metastatic potential. Risk is dominated by genotype: SDHB is
    the strongest predictor, with FH close behind, and both share the severe
    hypermethylator phenotype. Extra-adrenal primary site, larger tumor size and
    a dopaminergic (3-methoxytyramine-producing) biochemical profile add further
    risk. This node is the reason SDHB carriers receive the most intensive
    lifelong imaging surveillance. Germline risk is compounded by acquired
    somatic events: loss-of-function ATRX mutations recur specifically in
    SDHB-mutant tumors and are an independent outcome marker, and the resulting
    alternative lengthening of telomeres is a candidate therapeutic
    vulnerability. Somatic ATRX/TERT lesions are modeled here as a modifier of
    this node rather than as separate pathophysiology nodes, because they are
    acquired and not part of the germline predisposition axis this entry scopes.
  evidence:
  - reference: PMID:28162975
    reference_title: Comprehensive Molecular Characterization of Pheochromocytoma and Paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      our analysis confirmed SDHB germline mutations, ATRX somatic mutations and
      Ki-67 expression as clinical outcome markers
    explanation: >-
      TCGA confirmation that somatic ATRX mutation, alongside germline SDHB, marks
      aggressive clinical behavior.
  - reference: PMID:28162975
    reference_title: Comprehensive Molecular Characterization of Pheochromocytoma and Paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      three tumors had both SDHB germline and ATRX somatic mutations, a
      previously reported association
    explanation: >-
      Documents the co-occurrence of germline SDHB and somatic ATRX that concentrates
      metastatic risk in the SDHB subgroup.
  - reference: PMID:24334767
    reference_title: "Germline mutations in FH confer predisposition to malignant pheochromocytomas and paragangliomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Remarkably, FH-deficient PCC/PGLs display the same pattern of epigenetic
      deregulation as SDHB-mutated malignant PCC/PGL.
    explanation: >-
      Ties the shared hypermethylator phenotype of FH- and SDHB-deficient tumors
      to their shared metastatic tendency.
histopathology:
- name: Neuroendocrine Differentiation
  finding_term:
    preferred_term: Neuroendocrine differentiation
    term:
      id: NCIT:C43574
      label: Neuroendocrine Differentiation
  frequency: VERY_FREQUENT
  description: >-
    PPGLs are neuroendocrine tumors, and the histological finding asserted here
    is neuroendocrine differentiation of the tumor cells (chromogranin A and
    synaptophysin positivity in a Zellballen nesting pattern), which is what the
    bound NCIT term denotes.
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pheochromocytomas (PCC) and paragangliomas (PGL) are rare neuroendocrine tumors."
    explanation: Abstract characterizes PCC/PGL as rare neuroendocrine tumors.
- name: Loss of SDHB Immunohistochemical Staining
  finding_term:
    preferred_term: Loss of SDHB immunohistochemical expression
    term:
      id: NCIT:C156463
      label: Loss of Immunohistochemical Expression of Succinate Dehydrogenase (SDH) B
  diagnostic: true
  description: >-
    SDHB immunohistochemistry is the standard triage tool that decides who needs
    SDHx germline sequencing. Loss of any single SDH subunit destabilizes the
    whole complex II heterotetramer, so SDHB protein is lost from the tumor
    regardless of which SDH subunit gene is mutated - SDHB staining is therefore a
    readout for the entire SDHx group, not just for SDHB. Granular cytoplasmic
    staining is retained in normal cells of the intratumoral fibrovascular network,
    which serves as the internal positive control. Importantly, tumors from
    Cluster 2 and Cluster 1B syndromes (RET/MEN2, VHL, NF1) retain SDHB staining,
    so the stain also discriminates SDHx disease from the other hereditary
    syndromes.
  evidence:
  - reference: PMID:19576851
    reference_title: "An immunohistochemical procedure to detect patients with paraganglioma and phaeochromocytoma with germline SDHB, SDHC, or SDHD gene mutations: a retrospective and prospective analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SDHB protein expression was absent in all 102 phaeochromocytomas and
      paragangliomas with an SDHB, SDHC, or SDHD mutation, but was present in all
      65 paraganglionic tumours related to multiple endocrine neoplasia type 2,
      von Hippel-Lindau disease, and neurofibromatosis type 1.
    explanation: >-
      Demonstrates that SDHB IHC loss marks the SDHx group as a whole and is
      retained in MEN2/VHL/NF1 tumors, supporting its use as a discriminating
      triage test.
  - reference: PMID:19576851
    reference_title: "An immunohistochemical procedure to detect patients with paraganglioma and phaeochromocytoma with germline SDHB, SDHC, or SDHD gene mutations: a retrospective and prospective analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The sensitivity and specificity of the SDHB immunohistochemistry to detect
      the presence of an SDH mutation in the prospective series were 100% (95% CI
      87-100) and 84% (60-97), respectively.
    explanation: >-
      Quantifies the test performance underpinning the recommendation to sequence
      only SDHB-negative tumors.

phenotypes:
- category: Cardiovascular
  name: Hypertension
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >-
    Paroxysmal or sustained hypertension due to catecholamine excess. Episodes
    may be precipitated by physical activity, anesthesia, or certain medications.
  evidence:
  - reference: PMID:17156452
    reference_title: "Pheochromocytomas and secreting paragangliomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "An increase in the production of catecholamines causes symptoms (mainly headaches, palpitations and excess sweating) and signs (mainly hypertension, weight loss and diabetes) reflecting the effects of epinephrine and norepinephrine on alpha- and beta-adrenergic receptors."
    explanation: "Abstract lists hypertension among catecholamine-related signs."
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Signs % of presence Sustained hypertension 48% Paroxysmic hypertension 44% Hypertension 92%"
    explanation: >-
      Consecutive rows of the clinical-signs-frequency table (Table 1) of a 2024
      scoping review; the Hypertension row reads 92%, which falls in the
      VERY_FREQUENT band (80-99%).
  phenotype_term:
    preferred_term: Hypertension
    term:
      id: HP:0000822
      label: Hypertension
- category: Neurological
  name: Headache
  frequency: FREQUENT
  description: >-
    Severe headaches during hypertensive episodes are a classic symptom of
    catecholamine excess. Banded FREQUENT rather than VERY_FREQUENT: the
    scoping-review symptom table reports 59%, which falls in the 30-79% band.
  phenotype_term:
    preferred_term: Headache
    term:
      id: HP:0002315
      label: Headache
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Symptoms % of presence Dizziness 67% Headache 59%"
    explanation: >-
      Consecutive rows of the symptom-frequency table (Table 1) of a 2024
      scoping review; the Headache row reads 59%, which falls in the
      FREQUENT band (30-79%).
  - reference: PMID:17156452
    reference_title: "Pheochromocytomas and secreting paragangliomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "An increase in the production of catecholamines causes symptoms (mainly headaches, palpitations and excess sweating) and signs (mainly hypertension, weight loss and diabetes) reflecting the effects of epinephrine and norepinephrine on alpha- and beta-adrenergic receptors."
    explanation: Abstract explicitly names headache as a leading symptom of catecholamine excess in PPGL.
- category: Cardiovascular
  name: Palpitations
  frequency: FREQUENT
  description: >-
    Subjective awareness of forceful or rapid heartbeat during catecholamine
    surges, reported far more often than tachycardia is objectively recorded.
    Banded FREQUENT rather than VERY_FREQUENT: the scoping-review symptom table
    reports 50%.
  phenotype_term:
    preferred_term: Palpitations
    term:
      id: HP:0001962
      label: Palpitations
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Headache 59% Palpitations 50% Diaphoresis 50%"
    explanation: >-
      Consecutive rows of the symptom-frequency table (Table 1) of a 2024
      scoping review; the Palpitations row reads 50%, which falls in the
      FREQUENT band (30-79%).
  - reference: PMID:17156452
    reference_title: "Pheochromocytomas and secreting paragangliomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "An increase in the production of catecholamines causes symptoms (mainly headaches, palpitations and excess sweating) and signs (mainly hypertension, weight loss and diabetes) reflecting the effects of epinephrine and norepinephrine on alpha- and beta-adrenergic receptors."
    explanation: Abstract explicitly names palpitations as a leading symptom of catecholamine excess in PPGL.
- category: Constitutional
  name: Diaphoresis
  frequency: FREQUENT
  description: >-
    Excessive sweating during hypertensive paroxysms is a classic feature
    of pheochromocytoma.
  phenotype_term:
    preferred_term: Hyperhidrosis
    term:
      id: HP:0000975
      label: Hyperhidrosis
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Palpitations 50% Diaphoresis 50% Weight loss 30%"
    explanation: >-
      Consecutive rows of the symptom-frequency table (Table 1) of a 2024
      scoping review; the Diaphoresis row reads 50%, which falls in the
      FREQUENT band (30-79%).
  - reference: PMID:17156452
    reference_title: "Pheochromocytomas and secreting paragangliomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "An increase in the production of catecholamines causes symptoms (mainly headaches, palpitations and excess sweating) and signs (mainly hypertension, weight loss and diabetes) reflecting the effects of epinephrine and norepinephrine on alpha- and beta-adrenergic receptors."
    explanation: Abstract explicitly names excess sweating as a leading symptom of catecholamine excess in PPGL.
- category: Neoplasm
  name: Pheochromocytoma
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >-
    Catecholamine-producing tumor of the adrenal medulla. Bilateral and
    multifocal disease, and presentation at a younger age than sporadic tumors,
    are hallmarks of a hereditary syndrome and should prompt germline testing
    regardless of family history.
  phenotype_term:
    preferred_term: Pheochromocytoma
    term:
      id: HP:0002666
      label: Pheochromocytoma
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pheochromocytomas arise from chromaffin cells in the adrenal medulla, and
      PGLs arise from chromaffin cells in the ganglia of the autonomic nervous
      system.
    explanation: Defines the adrenal-medullary origin of pheochromocytoma.
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of these neuroendocrine tumors, 80-85% is PCCs, and 15-20% is PGLs."
    explanation: >-
      Quantifies pheochromocytoma as the predominant presentation, supporting the
      VERY_FREQUENT frequency band.
- category: Neoplasm
  name: Paraganglioma
  diagnostic: true
  description: >-
    Extra-adrenal tumor of sympathetic (thoracoabdominal, usually secretory) or
    parasympathetic (head-and-neck, usually non-secretory) paraganglia. SDHD and
    SDHAF2 carriers characteristically develop multifocal head-and-neck tumors;
    SDHB carriers characteristically develop abdominal sympathetic tumors.
    No frequency band is asserted because the proportion is strongly
    context-dependent: paraganglioma accounts for only 15-20% of all PPGL, but
    is the dominant and often multifocal presentation in SDHx-related hereditary
    disease.
  phenotype_term:
    preferred_term: Paraganglioma
    term:
      id: HP:0002668
      label: Paraganglioma
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Paragangliomas originate from sympathetic or parasympathetic ganglia in the
      abdomen, thorax, and pelvis.
    explanation: Defines the extra-adrenal sympathetic/parasympathetic origin.
  - reference: PMID:15328326
    reference_title: Distinct clinical features of paraganglioma syndromes associated with SDHB and SDHD gene mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Head and neck paragangliomas (10/32 vs 27/34, respectively, P<.001) and multifocal (9/32 vs 25/34, respectively, P<.001) tumors were more frequent in carriers of SDHD mutations."
    explanation: >-
      Supports the genotype-site correlation, with head-and-neck and multifocal
      paraganglioma concentrated in SDHD carriers.
- category: Neoplasm
  name: Renal Cell Carcinoma
  description: >-
    Part of the extended SDHx tumor spectrum beyond PPGL. SDH-deficient renal
    cell carcinoma is a recognized WHO entity and is a reason SDHx surveillance
    imaging covers the abdomen rather than only known tumor sites. Also occurs in
    TMEM127-related disease and, by a separate mechanism, in VHL disease.
  phenotype_term:
    preferred_term: Renal cell carcinoma
    term:
      id: HP:0005584
      label: Renal cell carcinoma
- category: Neoplasm
  name: Gastrointestinal Stromal Tumor
  description: >-
    SDH-deficient GIST, typically gastric, epithelioid, and KIT/PDGFRA-wildtype.
    The co-occurrence of paraganglioma and GIST in a germline SDHx carrier
    defines Carney-Stratakis syndrome, which is curated as a separate entry; the
    sporadic, non-germline, SDHC-promoter-hypermethylated counterpart with
    pulmonary chondroma is Carney triad.
  phenotype_term:
    preferred_term: Gastrointestinal stroma tumor
    term:
      id: HP:0100723
      label: Gastrointestinal stroma tumor
- category: Constitutional
  name: Pallor
  description: >-
    Cutaneous vasoconstriction during catecholamine paroxysms. Pallor rather than
    flushing is characteristic and helps distinguish PPGL from carcinoid syndrome
    and mast-cell disorders.
  phenotype_term:
    preferred_term: Pallor
    term:
      id: HP:0000980
      label: Pallor
- category: Neuropsychiatric
  name: Anxiety
  frequency: OCCASIONAL
  description: >-
    Episodic anxiety or a sense of impending doom accompanying catecholamine
    surges. This overlap with panic disorder is a common source of diagnostic
    delay.
  phenotype_term:
    preferred_term: Anxiety
    term:
      id: HP:0000739
      label: Anxiety
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Weight loss 30% Syncope episodes 40% Anxiety 19%"
    explanation: >-
      Consecutive rows of the symptom-frequency table (Table 1) of a 2024
      scoping review; the Anxiety row reads 19%, which falls in the
      OCCASIONAL band (5-29%).
- category: Neurological
  name: Dizziness
  frequency: FREQUENT
  description: >-
    Light-headedness or a spinning sensation during catecholamine paroxysms and
    on standing, driven by the combination of blood-pressure lability and
    catecholamine-induced plasma volume contraction. Reported as the single most
    common symptom in a 2024 scoping-review synthesis. Bound to the HPO term
    Vertigo (exact synonym 'dizzy spell'), which is the closest available class;
    the source reports the broader clinical term 'dizziness'.
  phenotype_term:
    preferred_term: Dizziness
    term:
      id: HP:0002321
      label: Vertigo
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Symptoms % of presence Dizziness 67%"
    explanation: >-
      Consecutive rows of the symptom-frequency table (Table 1) of a 2024
      scoping review; the Dizziness row reads 67%, which falls in the
      FREQUENT band (30-79%).
- category: Cardiovascular
  name: Syncope
  frequency: FREQUENT
  description: >-
    Transient loss of consciousness during paroxysms, reflecting abrupt swings
    between catecholamine-driven hypertension and the profound post-paroxysmal
    hypotension that follows receptor desensitization in a volume-contracted
    patient.
  phenotype_term:
    preferred_term: Syncope
    term:
      id: HP:0001279
      label: Syncope
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Weight loss 30% Syncope episodes 40% Anxiety 19%"
    explanation: >-
      Consecutive rows of the symptom-frequency table (Table 1) of a 2024
      scoping review; the Syncope episodes row reads 40%, which falls in the
      FREQUENT band (30-79%).
- category: Cardiovascular
  name: Tachycardia
  frequency: OCCASIONAL
  description: >-
    Beta-1-adrenergic chronotropic drive from circulating catecholamines.
    Recorded as an objective sign in a minority of patients even though
    subjective palpitations are reported by about half, which is why a resting
    heart rate of 85 bpm or higher carries a point in the published PPGL
    probability score.
  phenotype_term:
    preferred_term: Tachycardia
    term:
      id: HP:0001649
      label: Tachycardia
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypertension 92% Tachycardia 15% Orthostatic hypotension 12%"
    explanation: >-
      Consecutive rows of the clinical-signs-frequency table (Table 1) of a 2024
      scoping review; the Tachycardia row reads 15%, which falls in the
      OCCASIONAL band (5-29%).
- category: Cardiovascular
  name: Orthostatic Hypotension
  frequency: OCCASIONAL
  description: >-
    Chronic catecholamine excess contracts plasma volume and desensitizes
    adrenergic receptors, so a patient who is hypertensive when supine may drop
    their pressure sharply on standing. Clinically important because it is the
    physiological reason preoperative alpha-blockade must be paired with salt
    and fluid repletion.
  phenotype_term:
    preferred_term: Orthostatic hypotension
    term:
      id: HP:0001278
      label: Orthostatic hypotension
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypertension 92% Tachycardia 15% Orthostatic hypotension 12%"
    explanation: >-
      Consecutive rows of the clinical-signs-frequency table (Table 1) of a 2024
      scoping review; the Orthostatic hypotension row reads 12%, which falls in the
      OCCASIONAL band (5-29%).
- category: Constitutional
  name: Weight Loss
  frequency: FREQUENT
  description: >-
    Catecholamine-driven hypermetabolism and lipolysis. A low body mass index
    carries a point, and obesity a negative point, in the published PPGL
    probability score.
  phenotype_term:
    preferred_term: Weight loss
    term:
      id: HP:0001824
      label: Weight loss
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Diaphoresis 50% Weight loss 30% Syncope episodes 40%"
    explanation: >-
      Consecutive rows of the symptom-frequency table (Table 1) of a 2024
      scoping review; the Weight loss row reads 30%, which falls in the
      FREQUENT band (30-79%).
  - reference: PMID:17156452
    reference_title: Pheochromocytomas and secreting paragangliomas.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: An increase in the production of catecholamines causes symptoms (mainly headaches, palpitations and excess sweating) and signs (mainly hypertension, weight loss and diabetes) reflecting the effects of epinephrine and norepinephrine on alpha- and beta-adrenergic receptors.
    explanation: >-
      Independent review listing weight loss among the cardinal catecholamine-mediated
      signs.
- category: Endocrine
  name: Hyperglycemia
  description: >-
    Catecholamines suppress pancreatic beta-cell insulin release and promote
    hepatic glycogenolysis and gluconeogenesis, producing carbohydrate
    intolerance that often resolves after tumor resection. No frequency band is
    asserted because the cited sources describe the mechanism and list the sign
    without reporting a proportion.
  phenotype_term:
    preferred_term: Hyperglycemia
    term:
      id: HP:0003074
      label: Hyperglycemia
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Pancreas Carbohydrate intolerance due to Beta cells
    explanation: >-
      Table 1 row attributing carbohydrate intolerance to catecholamine-mediated
      changes in beta-cell regulation and insulin release suppression.
- category: Endocrine
  name: Diabetes Mellitus
  description: >-
    Sustained catecholamine-mediated insulin suppression and insulin resistance
    can present as new-onset diabetes, occasionally as the index abnormality
    that leads to the tumor being found. No frequency band is asserted; the
    cited review names diabetes as a cardinal sign without quantifying it.
  phenotype_term:
    preferred_term: Diabetes mellitus
    term:
      id: HP:0000819
      label: Diabetes mellitus
  evidence:
  - reference: PMID:17156452
    reference_title: Pheochromocytomas and secreting paragangliomas.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: An increase in the production of catecholamines causes symptoms (mainly headaches, palpitations and excess sweating) and signs (mainly hypertension, weight loss and diabetes) reflecting the effects of epinephrine and norepinephrine on alpha- and beta-adrenergic receptors.
    explanation: >-
      Lists diabetes among the cardinal signs produced by catecholamine excess.
- category: Neurological
  name: Tremor
  description: >-
    Episodic beta-adrenergic tremor, part of the paroxysmal sympathetic symptom
    cluster that is most pronounced in adrenergic (Cluster 2) tumors. No
    frequency band is asserted because the cited review scores tremor as a
    diagnostic-probability item rather than reporting its prevalence.
  phenotype_term:
    preferred_term: Tremor
    term:
      id: HP:0001337
      label: Tremor
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: tremor, anxiety/panic, and pallor, and older age
    explanation: >-
      Names tremor as part of the episodic sympathetic symptom presentation used
      to classify PPGL probability.
- category: Otolaryngologic
  name: Pulsatile Tinnitus
  description: >-
    Mass-effect symptom of head-and-neck (parasympathetic) paraganglioma rather
    than a catecholamine effect. Because roughly 95% of head-and-neck
    paragangliomas are non-secretory, these local symptoms - not paroxysms - are
    typically how SDHD/SDHAF2 carriers present, and they are invisible to
    metanephrine screening. No frequency band is asserted; the cited surgical
    series ranks the symptoms without giving proportions.
  phenotype_term:
    preferred_term: Tinnitus
    term:
      id: HP:0000360
      label: Tinnitus
  evidence:
  - reference: PMID:21691058
    reference_title: Management of vagal paragangliomas including application of internal carotid artery stenting.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The most common symptoms were hoarseness, tinnitus and hearing loss.
    explanation: >-
      Retrospective series of 22 vagal paragangliomas identifying tinnitus among
      the most common presenting symptoms.
- category: Otolaryngologic
  name: Hoarseness
  description: >-
    Dysphonia from vagal or recurrent-laryngeal-nerve involvement by a vagal or
    jugular paraganglioma, either from the tumor itself or as a consequence of
    resection. A lower-cranial-nerve deficit in a paraganglioma patient is a
    marker of skull-base or vagal location.
  phenotype_term:
    preferred_term: Dysphonia
    term:
      id: HP:0001618
      label: Dysphonia
  evidence:
  - reference: PMID:21691058
    reference_title: Management of vagal paragangliomas including application of internal carotid artery stenting.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The most common symptoms were hoarseness, tinnitus and hearing loss.
    explanation: >-
      Identifies hoarseness as a leading presenting symptom of vagal paraganglioma.
- category: Otolaryngologic
  name: Hearing Loss
  description: >-
    Conductive or sensorineural hearing loss from jugulotympanic or vagal
    paraganglioma involving the middle ear and temporal bone. Together with
    tinnitus and hoarseness it forms the local mass-effect presentation of
    non-secretory head-and-neck disease.
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  evidence:
  - reference: PMID:21691058
    reference_title: Management of vagal paragangliomas including application of internal carotid artery stenting.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The most common symptoms were hoarseness, tinnitus and hearing loss.
    explanation: >-
      Identifies hearing loss as a leading presenting symptom of vagal paraganglioma.
- category: Hematologic
  name: Polycythemia
  description: >-
    Specific to the Cluster 1B EPAS1/HIF2A gain-of-function form (Pacak-Zhuang
    syndrome), where stabilized HIF-2alpha drives erythropoietin transcription.
    Polycythemia accompanying paraganglioma is a strong pointer to an EPAS1
    lesion, frequently postzygotic mosaic and therefore potentially absent from
    blood-derived germline testing.
  phenotype_term:
    preferred_term: Polycythemia
    term:
      id: HP:0001901
      label: Polycythemia
  evidence:
  - reference: PMID:22931260
    reference_title: "Somatic HIF2A gain-of-function mutations in paraganglioma with polycythemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we report two novel somatic gain-of-function mutations in the gene
      encoding hypoxia-inducible factor 2α (HIF2A) in two patients, one presenting
      with paraganglioma and the other with paraganglioma and somatostatinoma,
      both of whom had polycythemia.
    explanation: >-
      Documents the paraganglioma-polycythemia association that characterizes the
      EPAS1/HIF2A subtype.
biochemical:
- name: Plasma Free Normetanephrine
  notes: >-
    Normetanephrine is the O-methylated metabolite of norepinephrine and is the
    single most informative analyte in hereditary PPGL, because SDHx and VHL
    (Cluster 1) tumors and extra-adrenal sympathetic paragangliomas are
    predominantly noradrenergic. Metabolism to metanephrines occurs continuously
    within the tumor rather than only on episodic catecholamine release, which is
    why fractionated metanephrines outperform measurement of the parent
    catecholamines. Samples should be drawn supine after at least 20-30 minutes of
    rest and interpreted against supine reference intervals; seated sampling is a
    common cause of false positives.
  reference_ranges:
  - loinc_term:
      id: LOINC:57462-4
      label: Normetanephrine Free [Mass/volume] in Serum or Plasma
    upper_bound: 0.9
    unit: nmol/L
    population: adults, supine sampling
    notes: >-
      Widely used adult supine upper reference limit; exact cutoffs are
      assay-, age- and posture-specific and must be taken from the reporting
      laboratory. Recorded here as an interpretive aid, not as a citable
      published interval - no primary citation is attached because the value is a
      laboratory convention rather than a single-study result.
    interpretation_bands:
    - name: Normal
      upper_bound: 0.9
      unit: nmol/L
      abnormal_flag: NORMAL
    - name: Equivocal elevation
      lower_bound: 0.9
      upper_bound: 2.7
      unit: nmol/L
      abnormal_flag: HIGH
      severity: MILD
      interpretation: >-
        Below roughly three times the upper reference limit. This is the band in
        which false positives dominate: confirm by repeating supine and drug-free,
        and consider clonidine suppression before imaging.
    - name: Diagnostic elevation
      lower_bound: 2.7
      unit: nmol/L
      abnormal_flag: CRITICAL_HIGH
      severity: SEVERE
      interpretation: >-
        At or above roughly three to four times the upper reference limit, the
        probability of a PPGL approaches certainty and the workflow moves directly
        to anatomical and functional localization.
- name: Plasma Free Metanephrine
  notes: >-
    Metanephrine is the O-methylated metabolite of epinephrine. Because
    epinephrine synthesis requires PNMT, which depends on the high local cortisol
    of the adrenal cortex, a metanephrine-predominant pattern implies an adrenal
    tumor and points toward the Cluster 2 genes (RET/MEN2, NF1, TMEM127) rather
    than toward SDHx. An isolated normetanephrine rise with a normal metanephrine
    is the expected SDHx/VHL pattern.
  reference_ranges:
  - loinc_term:
      id: LOINC:38494-1
      label: Metanephrine Free [Mass/volume] in Serum or Plasma
    upper_bound: 0.5
    unit: nmol/L
    population: adults, supine sampling
    notes: >-
      Conventional adult supine upper reference limit; assay-specific. Recorded as
      an interpretive aid rather than a citable published interval.
- name: Plasma Free 3-Methoxytyramine
  notes: >-
    The O-methylated metabolite of dopamine, and the reason a modern metanephrine
    panel is run as three analytes rather than two. An isolated or disproportionate
    3-methoxytyramine elevation identifies dopaminergic tumors, which are strongly
    enriched among SDHx-related, extra-adrenal, head-and-neck and metastatic
    disease - the very tumors most likely to be missed by a two-analyte panel,
    since dopamine-only secretors do not raise metanephrine or normetanephrine and
    do not produce the classic hypertensive paroxysms.
  reference_ranges:
  - loinc_term:
      id: LOINC:50140-3
      label: 3-Methoxytyramine [Moles/volume] in Serum or Plasma
    upper_bound: 0.1
    unit: nmol/L
    population: adults, supine sampling
    notes: >-
      Assay-specific upper reference limit, recorded as an interpretive aid.
      3-methoxytyramine is particularly sensitive to dietary interference and
      requires appropriate pre-analytical restriction.
- name: Urinary Catecholamines and Metanephrines
  notes: >-
    24-hour urine collection for catecholamines and metanephrines is an
    alternative biochemical test with high sensitivity.
genetic:
- name: SDHB
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: SDHB
    term:
      id: hgnc:10681
      label: SDHB
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    SDHB (1p36) mutations are associated with extra-adrenal sympathetic
    paraganglioma and the highest metastatic risk of any PPGL susceptibility
    gene. Lifelong surveillance required. Note that early estimates of both
    penetrance and metastatic rate were derived from clinically ascertained
    index cases and have been revised substantially downward in later
    population- and cascade-testing cohorts; see the discussions section.
  evidence:
  - reference: PMID:15328326
    reference_title: "Distinct clinical features of paraganglioma syndromes associated with SDHB and SDHD gene mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SDHB mutation carriers have an increased frequency of malignant disease (11/32 vs 0/34, P<.001)."
    explanation: JAMA study demonstrating significantly increased malignancy risk in SDHB mutation carriers compared to SDHD.
- name: SDHD
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: SDHD
    term:
      id: hgnc:10683
      label: SDHD
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    SDHD (11q23) mutations cause hereditary paraganglioma syndrome with
    predisposition to multifocal head and neck paragangliomas. Disease is
    expressed almost exclusively after paternal transmission; rare exceptions
    with maternal transmission are documented, so this is a strong parent-of-origin
    bias rather than an absolute rule.
  evidence:
  - reference: PMID:15328326
    reference_title: "Distinct clinical features of paraganglioma syndromes associated with SDHB and SDHD gene mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Head and neck paragangliomas (10/32 vs 27/34, respectively, P<.001) and multifocal (9/32 vs 25/34, respectively, P<.001) tumors were more frequent in carriers of SDHD mutations."
    explanation: JAMA study demonstrating SDHD mutations predispose to head and neck and multifocal paragangliomas.
- name: SDHC
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: SDHC
    term:
      id: hgnc:10682
      label: SDHC
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    SDHC (1q23) is an uncommon cause of predominantly head-and-neck
    paraganglioma with comparatively low metastatic risk and no parent-of-origin
    effect. Somatic SDHC promoter hypermethylation, rather than germline
    mutation, underlies Carney triad.
- name: SDHA
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: SDHA
    term:
      id: hgnc:10680
      label: SDHA
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    SDHA (5p15) encodes the catalytic flavoprotein subunit. Monoallelic germline
    loss confers low-penetrance PPGL and GIST predisposition. Biallelic SDHA loss
    causes mitochondrial complex II deficiency with Leigh syndrome, a
    non-neoplastic recessive disease curated separately - the same gene therefore
    supports two mechanistically distinct diseases depending on zygosity.
- name: SDHAF2
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: SDHAF2
    term:
      id: hgnc:26034
      label: SDHAF2
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    SDHAF2 (11q13) encodes an assembly factor required for flavination of the
    SDHA subunit; its loss disables complex II without mutating a structural
    subunit. The rarest PGL locus, presenting as multifocal head-and-neck
    paraganglioma, and, like SDHD, showing paternal-transmission-dependent
    expression.
  evidence:
  - reference: PMID:19628817
    reference_title: "SDH5, a gene required for flavination of succinate dehydrogenase, is mutated in paraganglioma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Sdh5 is required for SDH-dependent respiration and for Sdh1 flavination
      (incorporation of the flavin adenine dinucleotide cofactor).
    explanation: >-
      Defines the molecular function of SDHAF2/SDH5 that explains how its loss
      phenocopies loss of a structural SDH subunit.
- name: MAX
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: MAX
    term:
      id: hgnc:6913
      label: MAX
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    MAX (14q23) encodes the obligate dimerization partner of MYC. Loss
    deregulates the MYC-MAX-MXD1 network, placing MAX in the Cluster 2 group.
    Typically bilateral adrenal pheochromocytoma with an appreciable metastatic
    rate; preferential paternal transmission has been suggested but is less well
    established than for SDHD.
  evidence:
  - reference: PMID:21685915
    reference_title: "Exome sequencing identifies MAX mutations as a cause of hereditary pheochromocytoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We sequenced the exomes of three unrelated individuals with hereditary PCC
      (cases) and identified mutations in MAX, the MYC associated factor X gene.
    explanation: Original identification of MAX as a hereditary pheochromocytoma gene.
- name: TMEM127
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: TMEM127
    term:
      id: hgnc:26038
      label: TMEM127
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    TMEM127 (2q11) is a negative regulator of mTOR; loss produces
    NF1-like kinase-signaling tumors. Usually adrenal, frequently bilateral, low
    metastatic risk. Two-hit inactivation with consistent loss of the wild-type
    allele in tumor DNA.
  evidence:
  - reference: PMID:20154675
    reference_title: "Germline mutations in TMEM127 confer susceptibility to pheochromocytoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a cohort of 103 samples, we detected truncating germline TMEM127
      mutations in approximately 30% of familial tumors and about 3% of
      sporadic-appearing pheochromocytomas without a known genetic cause.
    explanation: >-
      Quantifies the contribution of TMEM127 to familial and apparently sporadic
      pheochromocytoma.
- name: FH
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: FH
    term:
      id: hgnc:3700
      label: FH
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    Fumarate hydratase loss produces fumarate accumulation - a second
    oncometabolite acting on the same 2-oxoglutarate-dependent dioxygenases as
    succinate - and therefore an 'SDH-like' hypermethylated, 5-hmC-low,
    2SC-positive tumor. FH belongs mechanistically with Cluster 1A and shares
    SDHB's enrichment for metastatic and multiple tumors. Germline FH also causes
    hereditary leiomyomatosis and renal cell cancer.
  evidence:
  - reference: PMID:24334767
    reference_title: "Germline mutations in FH confer predisposition to malignant pheochromocytomas and paragangliomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinically, metastatic phenotype (P = 0.007) and multiple tumors (P = 0.02)
      were significantly more frequent in patients with FH mutations than those
      without such mutations.
    explanation: >-
      Establishes the metastatic and multifocal enrichment that justifies
      including FH in PPGL genetic testing panels.
- name: EPAS1
  association: Gain-of-Function Variants, Frequently Postzygotic Mosaic
  gene_term:
    preferred_term: EPAS1
    term:
      id: hgnc:3374
      label: EPAS1
  notes: >-
    EPAS1 encodes HIF-2alpha. Gain-of-function variants escape prolyl
    hydroxylation and VHL-mediated degradation, giving Cluster 1B pseudohypoxia
    directly. Characteristically presents as multiple paragangliomas with
    polycythemia, with or without somatostatinoma (Pacak-Zhuang syndrome).
    Frequently postzygotic mosaic rather than germline, so a negative
    blood-derived panel does not exclude it - tumor tissue testing may be needed.
  evidence:
  - reference: PMID:22931260
    reference_title: "Somatic HIF2A gain-of-function mutations in paraganglioma with polycythemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The two mutations were associated with increased HIF-2α activity and
      increased protein half-life.
    explanation: >-
      Demonstrates the gain-of-function mechanism placing EPAS1 in Cluster 1B.
- name: VHL
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: VHL
    term:
      id: hgnc:12687
      label: VHL
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    VHL mutations cause von Hippel-Lindau syndrome with pheochromocytoma risk
    of 10-20%. Associated with clear cell renal cell carcinoma and other tumors.
    Cluster 1B. The full syndrome is curated in the Von Hippel-Lindau Disease
    entry; only the PPGL axis is modeled here.
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In 20% of the patients with VHL, PCC usually occurs and is seen at a young age."
    explanation: Documents VHL syndrome as a hereditary cause of pheochromocytoma with ~20% penetrance.
- name: RET
  association: Germline Activating Mutations
  gene_term:
    preferred_term: RET
    term:
      id: hgnc:9967
      label: RET
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    RET mutations in MEN2 syndrome cause pheochromocytoma in approximately
    50% of MEN2A and most MEN2B patients. Typically bilateral and benign.
    Cluster 2, adrenergic secretory profile. The full MEN2 syndrome, including
    medullary thyroid carcinoma and the codon-specific risk stratification that
    drives prophylactic thyroidectomy timing, is curated in the Multiple
    Endocrine Neoplasia Type 2 entry; only the PPGL axis is modeled here.
  evidence:
  - reference: PMID:32388798
    reference_title: "MEN2-related pheochromocytoma: current state of knowledge, specific characteristics in MEN2B, and perspectives."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Multiple endocrine neoplasia type 2 (MEN2) is a rare hereditary syndrome due to mutations of the proto-oncogene REarranged during Transfection (RET), defined by the association of medullary thyroid carcinoma (MTC) in almost 100% cases, and pheochromocytoma in roughly 50%"
    explanation: Review establishing RET mutations in MEN2 cause pheochromocytoma in approximately 50% of patients.
- name: NF1
  association: Germline Loss-of-Function Mutations
  gene_term:
    preferred_term: NF1
    term:
      id: hgnc:7765
      label: NF1
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    Neurofibromatosis type 1 is associated with pheochromocytoma in approximately
    1-5% of patients. Usually unilateral and benign. Cluster 2: neurofibromin is
    a RAS GTPase-activating protein, so its loss releases RAS-MAPK signaling.
    Because NF1 is usually diagnosed clinically from its cutaneous and neural
    features, NF1 is often omitted from PPGL gene panels. The full syndrome is
    curated in the Neurofibromatosis Type 1 entry; only the PPGL axis is modeled
    here.
  evidence:
  - reference: PMID:32617052
    reference_title: "Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PPGL develops in 1-5% of patients with NF-1. Almost all of these tumors are PCC, and PGL occurs rarely."
    explanation: Documents NF1 (neurofibromatosis type 1) as a hereditary cause of PPGL, predominantly pheochromocytoma.
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: INCOMPLETE
  penetrance_percentage: >-
    SDHB carriers 23.9% by age 60 and 30.6% by age 80 (ascertainment-adjusted
    retrospective cohort analysis); 21.8% by age 60 by Kaplan-Meier analysis of
    non-probands only
  description: >-
    All the established hereditary PPGL susceptibility genes are transmitted in
    an autosomal dominant fashion with respect to the predisposition allele,
    although tumor formation itself requires a somatic second hit. Penetrance is
    incomplete, age-dependent and strongly gene-specific, and estimates from
    clinically ascertained families are systematically higher than those from
    unbiased cascade or population testing. The figures recorded here are the
    ascertainment-adjusted SDHB estimates of Andrews et al. (2018), which are
    deliberately preferred over the widely quoted older values (for example ~50%
    or ~75% by age 50) precisely because those earlier estimates were derived
    from clinically ascertained probands. Recording the corrected numbers rather
    than omitting them is the point of the accompanying
    sdhb_penetrance_ascertainment_bias knowledge-gap discussion, which remains
    open because even the adjusted figures come from tertiary genetics referrals
    rather than a population cohort.
  evidence:
  - reference: PMID:29386252
    reference_title: Tumour risks and genotype-phenotype correlations associated with germline variants in succinate dehydrogenase subunit genes SDHB, SDHC and SDHD.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      With retrospective cohort analysis to adjust for ascertainment, cumulative
      tumour risks for SDHB mutation carriers at ages 60 years and 80 years were
      23.9% (95% CI 20.9% to 27.4%) and 30.6% (95% CI 26.8% to 34.7%).
    explanation: >-
      Source of the ascertainment-adjusted SDHB penetrance figures recorded in
      penetrance_percentage.
  - reference: PMID:29386252
    reference_title: Tumour risks and genotype-phenotype correlations associated with germline variants in succinate dehydrogenase subunit genes SDHB, SDHC and SDHD.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Overall risks of clinically apparent tumours for SDHB mutation carriers are
      substantially lower than initially estimated and will improve counselling
      of affected families.
    explanation: >-
      Supports the statement that clinically ascertained penetrance estimates are
      systematically inflated, which is why the older figures are not recorded here.
  - reference: PMID:16317055
    reference_title: Clinical presentation and penetrance of pheochromocytoma/paraganglioma syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, when all mutation carriers were included (n = 112), the estimated
      age-related penetrance was different for SDHB vs. SDHD mutation carriers (P
      = 0.008).
    explanation: >-
      International SDH Consortium result establishing that penetrance is
      age-dependent and gene-specific, which is why penetrance is recorded
      per-locus on the subtype inheritance blocks rather than as a single
      disease-level figure.
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Each child of an individual with a hereditary PGL/PCC syndrome-causing
      pathogenic variant has a 50% chance of inheriting the pathogenic variant.
    explanation: >-
      GeneReviews statement of the autosomal dominant transmission risk used in
      genetic counselling.
  - reference: PMID:15064708
    reference_title: Somatic loss of maternal chromosome 11 causes parent-of-origin-dependent inheritance in SDHD-linked paraganglioma and phaeochromocytoma families.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In SDHB (1p36)- and SDHC (1q21)-linked families, disease inheritance is
      autosomal dominant.
    explanation: >-
      Establishes standard autosomal dominant transmission for the non-imprinted
      SDHx loci, in contrast to the SDHD parent-of-origin pattern.
- name: Autosomal dominant with maternal imprinting (SDHD, SDHAF2)
  inheritance_term:
    preferred_term: Autosomal dominant inheritance with maternal imprinting
    term:
      id: HP:0012275
      label: Autosomal dominant inheritance with maternal imprinting
  penetrance: INCOMPLETE
  penetrance_percentage: >-
    Paternally inherited SDHD: 43.2% by age 60 (Kaplan-Meier analysis of
    non-probands). Maternally inherited SDHD carriers have a tumour risk
    approaching that of the general population.
  parent_of_origin_effect: >-
    Paternal transmission required for expression in SDHD and SDHAF2 (and
    possibly MAX); a strong bias rather than an absolute rule, since exceptions
    after maternal transmission are documented.
  description: >-
    SDHD- and SDHAF2-related disease shows a striking parent-of-origin effect:
    carriers who inherit the variant from their father are at high risk, while
    those who inherit the same variant from their mother very rarely develop
    tumors. Stated precisely, this is a strong bias and not an absolute law -
    rare, well-documented cases of disease after maternal transmission exist, so
    maternally inheriting carriers should still be counselled and offered
    surveillance rather than discharged. The HPO term 'maternal imprinting'
    denotes silencing of the maternally inherited copy, which is the correct
    orientation here; the underlying somatic event is loss of the entire maternal
    chromosome 11, so the phenomenon is not classical imprinting alone.
  evidence:
  - reference: PMID:15064708
    reference_title: "Somatic loss of maternal chromosome 11 causes parent-of-origin-dependent inheritance in SDHD-linked paraganglioma and phaeochromocytoma families."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In SDHD (11q23)-linked families, the disease phenotype is expressed only
      upon paternal transmission of the mutation, consistent with maternal
      imprinting.
    explanation: >-
      States the parent-of-origin pattern and its interpretation as maternal
      imprinting, matching the bound HPO term.
  - reference: PMID:15064708
    reference_title: "Somatic loss of maternal chromosome 11 causes parent-of-origin-dependent inheritance in SDHD-linked paraganglioma and phaeochromocytoma families."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, SDHD shows biallelic expression in brain, kidney and lymphoid
      tissues (Baysal et al., 2000).
    explanation: >-
      Qualifies the imprinting interpretation - SDHD is not uniformly silenced on
      the maternal allele, which is why the mechanism is better explained by
      somatic loss of maternal chromosome 11 than by classical imprinting.
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Pathogenic variants in SDHD, SDHAF2, and possibly MAX demonstrate
      parent-of-origin effects and cause disease almost exclusively when they are
      paternally inherited
    explanation: >-
      GeneReviews statement of the parent-of-origin rule, whose wording ('almost
      exclusively') is the basis for stating this as a strong bias rather than an
      absolute law.
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      an individual who inherits an SDHD or SDHAF2 pathogenic variant from the
      individual's mother is usually not at risk of developing disease
    explanation: >-
      Directly supports counselling maternally inheriting carriers as low-risk but
      not risk-free; GeneReviews immediately qualifies this with 'however,
      exceptions occur'.
treatments:
- name: Surgical Resection
  description: >-
    Complete surgical resection is the primary treatment for localized PPGL.
    Requires careful preoperative alpha-blockade followed by beta-blockade to
    prevent perioperative hypertensive crisis.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Definitive Surgical Resection
    term:
      id: NCIT:C154430
      label: Definitive Surgical Resection
  target_mechanisms:
  - target: Chromaffin Cell Tumorigenesis
    treatment_effect: INHIBITS
    description: >-
      Physical removal of the transformed chromaffin-cell mass. This is the only
      curative intervention in the entry and the only one that acts on the tumor
      itself rather than on a downstream signalling or secretory consequence.
  - target: Catecholamine Hypersecretion
    treatment_effect: INHIBITS
    description: >-
      Resection of a functional tumor abolishes the source of catecholamine
      excess, which is why cure of hypertension is the usual postoperative
      endpoint.
  evidence:
  - reference: PMID:24893135
    reference_title: "Pheochromocytoma and paraganglioma: an endocrine society clinical practice guideline."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "We recommend minimally invasive adrenalectomy for most pheochromocytomas with open resection for most paragangliomas."
    explanation: Endocrine Society clinical practice guideline recommending surgical resection as primary treatment.
- name: Alpha-Adrenergic Blockade
  description: >-
    Preoperative alpha-blockade with phenoxybenzamine or doxazosin is essential
    to control hypertension and allow volume expansion before surgery. Beta-blockade
    must never be started first: unopposed alpha-adrenergic stimulation after
    beta-blockade can precipitate a hypertensive crisis.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: phenoxybenzamine
      term:
        id: NCIT:C62065
        label: Phenoxybenzamine
    - preferred_term: doxazosin
      term:
        id: CHEBI:4708
        label: doxazosin
  target_mechanisms:
  - target: Catecholamine Hypersecretion
    treatment_effect: INHIBITS
    description: >-
      Blocks the alpha-adrenergic receptor endpoint of tumor-derived
      catecholamine excess. This is symptomatic control of the secretory
      consequence, not antitumor therapy.
  evidence:
  - reference: PMID:24893135
    reference_title: "Pheochromocytoma and paraganglioma: an endocrine society clinical practice guideline."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "All patients with functional PPGLs should undergo preoperative blockade to prevent perioperative complications."
    explanation: Endocrine Society guideline recommending preoperative alpha blockade for all functional PPGLs.
- name: MIBG Therapy
  description: >-
    131I-MIBG (metaiodobenzylguanidine) is a targeted radiotherapy for MIBG-avid
    metastatic PPGL. MIBG is a guanethidine analogue taken up by the
    noradrenaline transporter, which is what makes it selective for chromaffin
    tumors; roughly half of metastatic PPGLs are avid enough to be treatable.
    High-specific-activity 131I-MIBG (iobenguane I-131) is FDA-approved on the
    strength of a single-arm phase 2 trial in 68 patients whose primary endpoint
    was a durable halving of antihypertensive requirement - an unusual endpoint
    chosen because it measures the secretory burden rather than tumor bulk,
    which is why this treatment is modeled as acting on both the metastatic and
    the secretory nodes.
  therapeutic_modality: RADIOTHERAPY
  treatment_term:
    preferred_term: radiopharmaceutical therapy
    term:
      id: NCIT:C192439
      label: Radiopharmaceutical Therapy
    therapeutic_agent:
    - preferred_term: iobenguane I-131
      term:
        id: NCIT:C970
        label: Iobenguane I-131
  target_mechanisms:
  - target: Metastatic Progression
    treatment_effect: INHIBITS
    description: >-
      Delivers targeted beta radiation to noradrenaline-transporter-expressing
      metastatic deposits.
  - target: Catecholamine Hypersecretion
    treatment_effect: INHIBITS
    description: >-
      Reduction of secretory tumor mass lowers circulating catecholamines, which
      was operationalized as the trial's primary endpoint (durable reduction in
      antihypertensive medication requirement).
  evidence:
  - reference: PMID:30291194
    reference_title: Efficacy and Safety of High-Specific-Activity (131)I-MIBG Therapy in Patients with Advanced Pheochromocytoma or Paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Of the 68 patients who received at least 1 therapeutic dose of HSA
      131I-MIBG, 17 (25%; 95% confidence interval, 16%-37%) had a durable
      reduction in baseline antihypertensive medication use.
    explanation: >-
      Primary endpoint of the registrational phase 2 trial, supporting the
      secretory-burden target mechanism.
  - reference: PMID:30291194
    reference_title: Efficacy and Safety of High-Specific-Activity (131)I-MIBG Therapy in Patients with Advanced Pheochromocytoma or Paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Among 64 patients with evaluable disease, 59 (92%) had a partial response
      or stable disease as the best objective response within 12 mo.
    explanation: >-
      Radiographic disease-control result supporting the antitumor target mechanism.
  - reference: PMID:30291194
    reference_title: Efficacy and Safety of High-Specific-Activity (131)I-MIBG Therapy in Patients with Advanced Pheochromocytoma or Paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The median overall survival was 36.7 mo
    explanation: Survival outcome in the treated advanced-PPGL population.
- name: Temozolomide
  description: >-
    Alkylating chemotherapy showing activity in metastatic PPGL, particularly
    SDHB-mutated tumors with MGMT promoter methylation. The SDHB association is
    mechanistically coherent: the hypermethylator phenotype that makes SDHB
    tumors aggressive also silences the MGMT repair gene, which is what sensitizes
    them to an alkylating agent.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: chemotherapy
    term:
      id: NCIT:C15632
      label: Chemotherapy
    therapeutic_agent:
    - preferred_term: temozolomide
      term:
        id: CHEBI:72564
        label: temozolomide
  target_mechanisms:
  - target: Metastatic Progression
    treatment_effect: INHIBITS
    description: >-
      Cytotoxic control of metastatic disease, with enhanced activity in the
      MGMT-silenced, hypermethylated SDHB subgroup. Note that the
      hypermethylator node is a predictive biomarker here rather than a drug
      target: SDHB-driven MGMT promoter hypermethylation silences the repair
      enzyme that would otherwise reverse temozolomide's O6-methylguanine
      lesions, so no separate target_mechanisms edge is asserted against it.
  evidence:
  - reference: PMID:24752622
    reference_title: SDHB mutations are associated with response to temozolomide in patients with metastatic pheochromocytoma or paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Median PFS was 13.3 months after a median follow-up of 35 months. There
      were five partial responses (33%), seven stable (47%) and three
      progressive diseases (20%).
    explanation: >-
      Efficacy data from the retrospective series of 15 patients with progressive
      metastatic PPGL treated with temozolomide.
  - reference: PMID:24752622
    reference_title: SDHB mutations are associated with response to temozolomide in patients with metastatic pheochromocytoma or paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Partial responses were observed only in patients with mutation in SDHB.
    explanation: >-
      Establishes the SDHB genotype restriction of response that ties this
      treatment to the hypermethylator node.
  - reference: PMID:24752622
    reference_title: SDHB mutations are associated with response to temozolomide in patients with metastatic pheochromocytoma or paraganglioma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SDHB germline mutation was associated with hypermethylation of the MGMT
      promoter and low expression of MGMT in 190 samples of the French
      nation-wide independent cohort.
    explanation: >-
      Provides the mechanistic link - MGMT silencing by the SDHB hypermethylator
      phenotype - underpinning the SDHB-restricted response.
- name: Cyclophosphamide-Vincristine-Dacarbazine (CVD) Chemotherapy
  description: >-
    The conventional cytotoxic backbone for rapidly progressive or high-burden
    metastatic PPGL, and the comparator against which every newer systemic
    option is judged. A meta-analysis of four studies (50 patients) found a
    partial tumor-volume response in about 37% and a partial catecholamine
    response in about 40%. The authors are explicit that the studies did not
    define when treatment should start, so part of the apparent benefit may
    reflect the indolent natural history of PPGL - which is precisely why CVD is
    reserved for documented progression rather than used on diagnosis of
    metastatic disease.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: chemotherapy
    term:
      id: NCIT:C15632
      label: Chemotherapy
    therapeutic_agent:
    - preferred_term: cyclophosphamide
      term:
        id: CHEBI:4027
        label: cyclophosphamide
    - preferred_term: vincristine
      term:
        id: CHEBI:28445
        label: vincristine
    - preferred_term: dacarbazine
      term:
        id: CHEBI:4305
        label: dacarbazine
  target_mechanisms:
  - target: Metastatic Progression
    treatment_effect: INHIBITS
    description: >-
      Non-targeted cytotoxic control of metastatic tumor burden.
  - target: Catecholamine Hypersecretion
    treatment_effect: INHIBITS
    description: >-
      Tumor-burden reduction translates into a measurable hormonal response,
      reported separately from the radiographic response in the meta-analysis.
  evidence:
  - reference: PMID:25041164
    reference_title: 'Chemotherapy with cyclophosphamide, vincristine and dacarbazine for malignant paraganglioma and pheochromocytoma: systematic review and meta-analysis.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Data on the effects of a combination of CVD chemotherapy on malignant
      paraganglioma/pheochromocytoma suggest that a partial response concerning
      tumour volume can be achieved in about 37% of patients and a partial
      response on catecholamine excess in about 40% of patients.
    explanation: >-
      Pooled efficacy estimate supporting both the antitumor and the
      antisecretory target mechanisms.
  - reference: PMID:25041164
    reference_title: 'Chemotherapy with cyclophosphamide, vincristine and dacarbazine for malignant paraganglioma and pheochromocytoma: systematic review and meta-analysis.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Therefore, it cannot be excluded that the reported effect of chemotherapy
      on tumour volume reflects the natural course of the disease, at least
      partially.
    explanation: >-
      The authors' own caveat; recorded as PARTIAL because it qualifies rather
      than establishes the efficacy claim.
- name: Cabozantinib
  description: >-
    An antiangiogenic multi-tyrosine-kinase inhibitor (VEGFR2, MET, AXL) with the
    strongest prospective response data of any systemic agent in metastatic PPGL
    outside belzutifan. In the single-arm phase 2 Natalie Trial (NCT02302833,
    17 patients) the overall response rate was 25%. The rationale is the same
    pseudohypoxia-driven angiogenic program that motivates sunitinib, and the
    trial rationale explicitly invokes the SDHB-associated, angiogenesis-high
    phenotype that dominates hereditary metastatic disease.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: targeted therapy
    term:
      id: NCIT:C93352
      label: Targeted Therapy
    therapeutic_agent:
    - preferred_term: cabozantinib
      term:
        id: CHEBI:72317
        label: cabozantinib
  target_mechanisms:
  - target: Angiogenic and Glycolytic Tumor Program
    treatment_effect: INHIBITS
    description: >-
      Blocks VEGFR2-driven neovascularization downstream of the pseudohypoxic HIF
      program, the same node targeted by sunitinib.
  evidence:
  - reference: PMID:38608693
    reference_title: 'Cabozantinib in patients with unresectable and progressive metastatic phaeochromocytoma or paraganglioma (the Natalie Trial): a single-arm, phase 2 trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The overall response rate was 25·0% (95% CI 7·3-52·4; four of 16 patients).
    explanation: >-
      Primary efficacy endpoint of the phase 2 Natalie Trial.
  - reference: PMID:38608693
    reference_title: 'Cabozantinib in patients with unresectable and progressive metastatic phaeochromocytoma or paraganglioma (the Natalie Trial): a single-arm, phase 2 trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Up to 50% of MPPGs are associated with germline pathogenic variants of the
      SDHB gene. These tumours and many non-familial MPPGs exhibit a phenotype
      that is characterised by abnormal angiogenesis.
    explanation: >-
      States the hereditary-SDHB and angiogenesis rationale that links this drug
      to the angiogenic-program node.
- name: Sunitinib
  description: >-
    Multi-kinase inhibitor (VEGFR1-3, PDGFR-alpha/beta, KIT, FLT3, RET) with
    antiangiogenic activity in progressive metastatic PPGL. No longer
    prospective-data-poor: FIRSTMAPP, a randomized placebo-controlled phase 2
    trial, met its primary endpoint with a 12-month progression-free survival of
    36% versus 19% on placebo. Sunitinib also hits RET, so it has a second
    rationale in the Cluster 2 kinase arm on top of the Cluster 1 antiangiogenic
    one, though FIRSTMAPP was not powered for a genotype split.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: targeted therapy
    term:
      id: NCIT:C93352
      label: Targeted Therapy
    therapeutic_agent:
    - preferred_term: sunitinib
      term:
        id: CHEBI:38940
        label: sunitinib
  target_mechanisms:
  - target: Angiogenic and Glycolytic Tumor Program
    treatment_effect: INHIBITS
    description: >-
      Inhibits VEGFR/PDGFR signaling downstream of the pseudohypoxic HIF program,
      which is the rationale for anti-angiogenic activity being greatest in
      Cluster 1 tumors.
  - target: Kinase Signaling Activation
    treatment_effect: INHIBITS
    description: >-
      Sunitinib additionally inhibits RET, giving it a secondary rationale
      against the Cluster 2 kinase arm; this is a mechanistic inference from the
      drug's target profile rather than a genotype-stratified trial result.
  evidence:
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      recently reported that Sunitinib achieved the primary endpoint of 12-month
      progression-free survival in 36% of patients with progressive metastatic
      PPGL (90% CI, 23 –50%), compared to 19% in the placebo group (90% CI, 11
      –31%).
    explanation: >-
      FIRSTMAPP, a phase II randomized placebo-controlled trial, is the source of
      this result; it establishes sunitinib efficacy in progressive metastatic
      PPGL. The quote begins at 'recently reported' because the preceding words
      'placebo- controlled' carry a PDF line-break artifact in the cache, and the
      en-dashes in the confidence intervals are the cache's own U+2013
      characters, reproduced verbatim.
  - reference: PMID:39735644
    reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sunitinib, which inhibits VEGF1, VEGF2, VEGF3, PDGF-alpha, PDGF-beta, c- kit, fms-related tyrosine kinase 3, and RET proto-oncogene receptors, has demonstrated potential in reducing angiogenesis and tumor cell growth."
    explanation: >-
      Target profile supporting both the antiangiogenic and the RET/Cluster 2
      target mechanisms. (The space inside 'c- kit' is a PDF line-break artifact
      of the cached full text, reproduced verbatim so the snippet matches; kept
      on a single quoted line because a folded scalar cannot end a line in a
      hyphen.)
- name: Belzutifan
  description: >-
    A HIF-2alpha inhibitor that disrupts the HIF-2alpha/HIF-1beta heterodimer,
    directly antagonizing the pseudohypoxic node on which every Cluster 1 lesion
    converges. In the phase 2 LITESPARK-015 trial in advanced PPGL it produced a
    26% confirmed objective response rate with 85% disease control and a median
    progression-free survival of 22.3 months. Notably, a third of participants on
    antihypertensives were able to halve at least one agent, indicating the drug
    also reduces the secretory burden and not only tumor bulk. Grade 3 anemia
    (an on-target consequence of HIF-2-driven erythropoietin suppression) occurred
    in 22%.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: targeted therapy
    term:
      id: NCIT:C93352
      label: Targeted Therapy
    therapeutic_agent:
    - preferred_term: belzutifan
      term:
        id: NCIT:C135627
        label: Belzutifan
  target_mechanisms:
  - target: Pseudohypoxia and HIF Activation
    treatment_effect: INHIBITS
    description: >-
      Directly inhibits HIF-2alpha, the shared convergence point of Cluster 1A
      (oncometabolite-mediated PHD inhibition) and Cluster 1B (VHL/EPAS1)
      lesions. This is the drug-target pattern that makes the pseudohypoxia node
      clinically actionable.
  evidence:
  - reference: PMID:41124218
    reference_title: "Belzutifan for Advanced Pheochromocytoma or Paraganglioma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most cases of metastatic pheochromocytoma and paraganglioma are driven by
      dysregulation of the hypoxia-inducible factor 2α (HIF-2α) pathway.
    explanation: >-
      States the mechanistic rationale linking the treatment to the pseudohypoxia
      pathophysiology node.
  - reference: PMID:41124218
    reference_title: "Belzutifan for Advanced Pheochromocytoma or Paraganglioma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the percentage of participants with disease control was 85% (95% CI, 74 to
      92)
    explanation: >-
      Primary efficacy result of the phase 2 LITESPARK-015 trial supporting
      belzutifan activity in advanced PPGL.
- name: Peptide Receptor Radionuclide Therapy (177Lu-DOTATATE)
  description: >-
    Somatostatin-receptor-targeted radionuclide therapy for progressive
    metastatic PPGL, exploiting the high SSTR2 expression of these tumors that
    also underlies 68Ga-DOTATATE PET imaging. A phase 2 trial showed a 6-month
    progression-free survival rate of 0.861 overall, but with a clinically
    important genotype split: SDHx-mutated patients did significantly worse than
    apparently sporadic patients. A distinctive hazard is catecholamine release
    syndrome from radiation-induced tumor lysis, seen at grade 3 or above in 17%,
    which is why pretreatment alpha-blockade and sometimes planned intensive-care
    monitoring are used.
  therapeutic_modality: RADIOTHERAPY
  treatment_term:
    preferred_term: peptide receptor radionuclide therapy
    term:
      id: NCIT:C192439
      label: Radiopharmaceutical Therapy
    therapeutic_agent:
    - preferred_term: Lutetium Lu 177 dotatate
      term:
        id: NCIT:C95020
        label: Lutetium Lu 177 Dotatate
  target_mechanisms:
  - target: Metastatic Progression
    treatment_effect: INHIBITS
    description: >-
      Delivers targeted beta radiation to SSTR-expressing metastatic deposits.
  evidence:
  - reference: PMID:40829092
    reference_title: "Phase II Study of (177)Lu-DOTATATE for Progressive Metastatic Pheochromocytomas and Paragangliomas: Interim Analysis of Efficacy, Safety, and Biomarkers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Six-month PFS rate for all patients was 0.861 (95% CI, 0.755 to 0.982),
      which was significantly lower (P = .009) for SDHx at 0.72 (95% CI, 0.542 to
      0.962) versus sporadic at 1.00 (95% CI, 1.0 to 1.0).
    explanation: >-
      Documents both the overall efficacy and the genotype-dependent difference in
      benefit that is directly relevant to hereditary SDHx disease.
  - reference: PMID:40829092
    reference_title: "Phase II Study of (177)Lu-DOTATATE for Progressive Metastatic Pheochromocytomas and Paragangliomas: Interim Analysis of Efficacy, Safety, and Biomarkers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A 17% incidence of grade 3+ catecholamine release syndrome (CRS) was noted,
      which may benefit from preemptive ICU admission.
    explanation: >-
      Documents the catecholamine release syndrome hazard specific to treating
      secretory PPGL with radionuclide therapy.
- name: Genetic Testing and Cascade Screening
  description: >-
    Germline testing is recommended for all patients with PPGL, not only those
    with a family history, because roughly 40% carry a germline variant and
    a substantial minority of apparently sporadic presentations are hereditary. A
    positive result changes surveillance intensity, informs the site and
    biochemical phenotype to expect, predicts metastatic risk (SDHB highest), and
    enables cascade testing of relatives. SDHB immunohistochemistry on resected
    tumor is a cost-effective way to triage which patients need SDHx sequencing.
    For SDHD and SDHAF2, the parent-of-origin effect must be explained carefully
    during counselling.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The diagnosis is established in a proband with a personal or family history
      of paraganglioma or pheochromocytoma and a germline heterozygous pathogenic
      variant in MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD, or TMEM127 identified by
      molecular genetic testing.
    explanation: >-
      GeneReviews statement of the molecular diagnostic strategy and the gene
      panel that defines a hereditary PGL/PCC syndrome.
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      First-degree relatives of an individual with a hereditary PGL/PCC syndrome
      and a known MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD, or TMEM127 pathogenic
      variant should be offered molecular genetic testing to clarify their
      genetic status
    explanation: >-
      GeneReviews recommendation underpinning the cascade-testing component of
      this action.
- name: Lifelong Surveillance for Carriers
  description: >-
    Asymptomatic pathogenic-variant carriers enter risk-adapted lifelong
    surveillance, typically combining periodic plasma free metanephrines with
    whole-body MRI at intervals set by genotype. SDHB carriers receive the most
    intensive imaging because of their metastatic risk, while SDHD carriers need
    dedicated head-and-neck coverage for multifocal parasympathetic tumors that
    may be biochemically silent and therefore invisible to metanephrine testing
    alone.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: surveillance for hereditary PPGL
    term:
      id: NCIT:C15406
      label: Cancer Screening
  evidence:
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Individuals at risk for hereditary PGL/PCC syndromes should have annual
      clinical assessment for manifestations of PGL/PCCs and GISTs, plasma-free
      fractionated metanephrines or 24-hour urine fractionated metanephrines
      every two years in childhood and then annually in adults, and whole-body
      MRI every two to three years.
    explanation: >-
      GeneReviews surveillance schedule, the source of the biochemical-plus-MRI
      protocol described here.
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Age of initiation for screening varies by gene.
    explanation: >-
      Supports the genotype-adapted framing of the surveillance schedule rather
      than a single protocol for all carriers.
  - reference: PMID:20301715
    reference_title: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      approximately 95% of such tumors are nonsecretory
    explanation: >-
      Quantifies why head-and-neck coverage cannot rely on metanephrine testing -
      almost all head-and-neck paragangliomas are biochemically silent.
clinical_trials:
- name: NCT03206060
  phase: PHASE_II
  status: RECRUITING
  description: >-
    Phase 2 study of 177Lu-DOTATATE (Lutathera) in inoperable or metastatic
    pheochromocytoma/paraganglioma, with eligibility gated on somatostatin-receptor
    positivity demonstrated by 68Ga-DOTATATE PET/CT. This is the trial whose
    interim analysis (PMID:40829092) supplies the efficacy and
    catecholamine-release-syndrome data recorded on the PRRT treatment,
    including the SDHx-versus-sporadic progression-free-survival split that
    makes it directly relevant to the hereditary axis.
  target_phenotypes:
  - preferred_term: Paraganglioma
    term:
      id: HP:0002668
      label: Paraganglioma
  - preferred_term: Pheochromocytoma
    term:
      id: HP:0002666
      label: Pheochromocytoma
  evidence:
  - reference: clinicaltrials:NCT03206060
    reference_title: Lu-177-DOTATATE (Lutathera) in Therapy of Inoperable Pheochromocytoma/ Paraganglioma
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Adults who have an inoperable tumor of the study cancer that can be detected
      with Ga-68-DOTATATE PET/CT imaging
    explanation: >-
      Eligibility criterion confirming the somatostatin-receptor-directed rationale
      that links this trial to the PRRT treatment entry.
- name: NCT02302833
  phase: PHASE_II
  status: COMPLETED
  description: >-
    The Natalie Trial - single-arm phase 2 study of cabozantinib in unresectable,
    progressive metastatic pheochromocytoma/paraganglioma. Reported an overall
    response rate of 25% (PMID:38608693) and is the evidence base for the
    cabozantinib treatment entry.
  target_phenotypes:
  - preferred_term: Paraganglioma
    term:
      id: HP:0002668
      label: Paraganglioma
  - preferred_term: Pheochromocytoma
    term:
      id: HP:0002666
      label: Pheochromocytoma
  evidence:
  - reference: clinicaltrials:NCT02302833
    reference_title: A Phase II Study to Evaluate the Effects of Cabozantinib in Patients With Unresectable Metastatic Pheochromocytomas and Paragangliomas
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cabozantinib s-malate may stop the growth of tumor cells by blocking some of
      the enzymes needed for cell growth and by blocking the growth of new blood
      vessels necessary for tumor growth.
    explanation: >-
      Trial summary stating the antiangiogenic mechanism that connects cabozantinib
      to the Angiogenic and Glycolytic Tumor Program node.
differential_diagnoses:
- name: Von Hippel-Lindau disease
  description: >-
    VHL is itself one of the hereditary PPGL genes (Cluster 1B), so the question
    is rarely 'PPGL or VHL' but rather whether a PPGL is the presenting feature of
    VHL disease. VHL-related pheochromocytoma is usually adrenal, often bilateral,
    noradrenergic, and has low metastatic potential.
  distinguishing_features:
  - >-
    Presence of the wider VHL tumor spectrum - retinal and CNS hemangioblastoma,
    clear cell renal cell carcinoma, pancreatic neuroendocrine tumor,
    endolymphatic sac tumor.
  - >-
    SDHB immunohistochemistry is retained (positive) in VHL tumors and lost in
    SDHx tumors, which resolves the distinction on the resection specimen.
  disease_term:
    preferred_term: von Hippel-Lindau disease
    term:
      id: MONDO:0008667
      label: von Hippel-Lindau disease
  notes: Curated in full as a separate entry (Von_Hippel-Lindau_Disease).
  evidence:
  - reference: PMID:19576851
    reference_title: "An immunohistochemical procedure to detect patients with paraganglioma and phaeochromocytoma with germline SDHB, SDHC, or SDHD gene mutations: a retrospective and prospective analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SDHB protein expression was absent in all 102 phaeochromocytomas and
      paragangliomas with an SDHB, SDHC, or SDHD mutation, but was present in all
      65 paraganglionic tumours related to multiple endocrine neoplasia type 2,
      von Hippel-Lindau disease, and neurofibromatosis type 1.
    explanation: >-
      Supports SDHB immunohistochemistry as the discriminator between SDHx disease
      and the VHL/MEN2/NF1 syndromes.
- name: Multiple endocrine neoplasia type 2
  description: >-
    RET-driven MEN2 accounts for a substantial share of hereditary
    pheochromocytoma. Pheochromocytoma occurs in roughly half of MEN2A patients
    and most MEN2B patients, and is typically bilateral, adrenal, adrenergic and
    rarely metastatic.
  distinguishing_features:
  - >-
    Medullary thyroid carcinoma (near-universal in MEN2 and usually the
    presenting tumor), hyperparathyroidism in MEN2A, and the mucosal
    neuroma/marfanoid habitus of MEN2B.
  - >-
    Biochemically metanephrine-predominant (adrenergic), whereas SDHx disease is
    normetanephrine-predominant. SDHB staining is retained.
  disease_term:
    preferred_term: multiple endocrine neoplasia type 2
    term:
      id: MONDO:0019003
      label: multiple endocrine neoplasia type 2
  notes: Curated in full as a separate entry (Multiple_Endocrine_Neoplasia_Type_2).
- name: Neurofibromatosis type 1
  description: >-
    NF1 confers a small (roughly 1-5%) lifetime pheochromocytoma risk. Because
    NF1 is diagnosed clinically it is frequently absent from PPGL gene panels, so
    the diagnosis rests on recognizing the syndrome rather than on sequencing.
  distinguishing_features:
  - >-
    Cafe-au-lait macules, skinfold freckling, cutaneous and plexiform
    neurofibromas, Lisch nodules, optic pathway glioma.
  - NF1-related tumors are adrenal and adrenergic, and retain SDHB staining.
  disease_term:
    preferred_term: neurofibromatosis type 1
    term:
      id: MONDO:0018975
      label: neurofibromatosis type 1
  notes: Curated in full as a separate entry (Neurofibromatosis_Type_1).
- name: Carney-Stratakis syndrome
  description: >-
    The dyad of paraganglioma and gastrointestinal stromal tumor caused by
    germline SDHB, SDHC or SDHD variants. This is not a separate mechanism from
    hereditary PPGL but a phenotypic presentation of the same SDHx lesion, and
    the boundary is defined by the presence of GIST.
  distinguishing_features:
  - >-
    Co-occurrence of SDH-deficient (KIT/PDGFRA-wildtype, gastric, epithelioid)
    GIST with paraganglioma in a germline SDHx carrier.
  - >-
    Distinguished from Carney triad, which adds pulmonary chondroma, shows strong
    female predominance, is usually caused by somatic SDHC promoter
    hypermethylation rather than a germline variant, and is typically not
    inherited.
  disease_term:
    preferred_term: Carney-Stratakis syndrome
    term:
      id: MONDO:0011740
      label: Carney-Stratakis syndrome
  notes: Curated in full as a separate entry (Carney-Stratakis_Syndrome).
- name: Essential hypertension
  description: >-
    By far the most common alternative explanation for the presenting complaint.
    PPGL accounts for well under 1% of hypertension in outpatient practice, so
    the pre-test probability is low and false-positive biochemistry is a real
    clinical hazard.
  distinguishing_features:
  - >-
    Absence of paroxysmal symptoms, normal fractionated metanephrines, and no
    adrenal or extra-adrenal mass on imaging.
  - >-
    Metanephrine elevations below about three times the upper reference limit are
    more often explained by posture, stress, or interfering medication (tricyclics,
    MAO inhibitors, sympathomimetics) than by a tumor.
- name: Panic disorder and anxiety disorders
  description: >-
    Episodic palpitations, sweating, tremor and a sense of impending doom overlap
    closely with catecholamine paroxysms, and this overlap is a frequent cause of
    diagnostic delay in both directions.
  distinguishing_features:
  - >-
    Panic attacks are typically not accompanied by the marked objective
    hypertension and pallor of a catecholamine paroxysm; flushing is more typical
    of anxiety.
  - Fractionated metanephrines are normal.
- name: Carcinoid syndrome and other neuroendocrine tumors
  description: >-
    Other neuroendocrine tumors can produce episodic vasoactive symptoms and,
    like PPGL, are somatostatin-receptor-positive on 68Ga-DOTATATE PET, so
    functional imaging alone does not separate them.
  distinguishing_features:
  - >-
    Carcinoid syndrome causes flushing and secretory diarrhea rather than pallor
    and hypertension.
  - >-
    Associated with elevated urinary 5-HIAA and chromogranin A rather than
    fractionated metanephrines.
- name: Adrenocortical adenoma or carcinoma
  description: >-
    The commonest competing diagnosis for an incidentally discovered adrenal
    mass. Distinguishing these before surgery matters, because operating on an
    unrecognized pheochromocytoma without alpha-blockade risks intraoperative
    hypertensive crisis.
  distinguishing_features:
  - >-
    Adrenocortical lesions are lipid-rich with low unenhanced CT attenuation
    (10 Hounsfield units or less) and rapid contrast washout, whereas
    pheochromocytomas are lipid-poor and markedly T2-hyperintense on MRI.
  - >-
    Every adrenal incidentaloma should have metanephrines measured before any
    planned resection or biopsy.
disease_term:
  preferred_term: pheochromocytoma-paraganglioma
  term:
    id: MONDO:0035540
    label: pheochromocytoma-paraganglioma

classifications:
  harrisons_chapter:
  - classification_value: ONCOLOGY_HEMATOLOGY
discussions:
- discussion_id: sdhb_penetrance_ascertainment_bias
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What is the true age-related penetrance of SDHB pathogenic variants in
    carriers ascertained without a personal or family history of tumor?
  attaches_to:
  - pathophysiology#Metastatic Progression
  rationale: >-
    Early penetrance and metastatic-risk estimates for SDHB were derived from
    clinically ascertained index cases and affected families, which
    systematically overestimates risk. Later cascade-testing and population
    series have revised penetrance substantially downward. This matters
    practically rather than academically: surveillance intensity, the age at
    which imaging starts, and the counselling given to an unaffected relative who
    tests positive all depend on which estimate is used. The gap is widening as
    incidental identification of SDHB variants on broad panels becomes common.
  proposed_experiments:
  - experiment_id: exp_sdhb_unbiased_population_penetrance_cohort
    name: Unbiased population-ascertained SDHB carrier penetrance cohort
    description: >-
      Prospective follow-up of unselected SDHB carriers identified through
      population-scale biobank sequencing rather than clinical referral, with
      standardized imaging, reporting age-specific cumulative incidence
      separately for carriers with and without a family history.
- discussion_id: cluster_prediction_of_belzutifan_response
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Does molecular cluster assignment (Cluster 1A SDHx/FH versus Cluster 1B
    VHL/EPAS1 versus Cluster 2 kinase-signaling) predict response to HIF-2alpha
    inhibition with belzutifan?
  attaches_to:
  - pathophysiology#Pseudohypoxia and HIF Activation
  rationale: >-
    The mechanistic rationale for belzutifan is that Cluster 1 tumors are driven
    by HIF-2alpha, which predicts that Cluster 1 disease should respond
    preferentially and that Cluster 2 disease should not. The registrational
    phase 2 trial was not stratified or powered to test this, reporting a 26%
    objective response rate across an unselected advanced-PPGL population. If the
    prediction holds, cluster assignment becomes a treatment-selection biomarker;
    if responses are distributed evenly across clusters, the assumed mechanism of
    benefit in PPGL is incomplete. This is an explicitly open question in the
    current literature.
  proposed_experiments:
  - experiment_id: exp_belzutifan_response_by_molecular_cluster
    name: Belzutifan response stratified by molecular cluster
    description: >-
      Prespecified biomarker analysis of response by germline and somatic driver
      and by transcriptional cluster within belzutifan-treated cohorts, ideally
      pooled across trials to reach adequate numbers in the smaller genotype
      groups.
notes: >-
  Scope and boundary notes. (1) This entry covers the hereditary
  predisposition-syndrome axis (MONDO:0017366) alongside the tumor entity
  (MONDO:0035540) following the curation decision recorded on issue #7475, rather
  than as a separate Disease entry. (2) VHL, MEN2/RET, NF1 and Carney-Stratakis
  are each curated as their own entries; only their PPGL axis is modeled here and
  they are cross-referenced from differential_diagnoses and genetic. (3) No
  icdo_morphology classification is asserted because the closed
  ICDOMorphologyEnum offers only Carcinoma, Adenocarcinoma, Squamous Cell
  Carcinoma, Sarcoma, Leukemia, Lymphoma, Multiple Myeloma, Melanoma, Glioma and
  Embryonal Neoplasm - none of which is a correct parent for paraganglioma
  (ICD-O 8680/1) or pheochromocytoma (8700/0). This is a noted enum gap rather
  than an omission. (4) PGL6 (SLC25A11) and PGL7 (DLST) exist as MONDO/OMIM
  entities but are not modeled as subtypes here; the MONDO records carry no
  definition text, so the locus-to-gene assignment could not be verified to the
  standard applied to PGL1-PGL5 and was deliberately left out rather than
  asserted on recall. (5) Cluster 3 (Wnt-altered) PPGL - somatic MAML3 fusions
  and CSDE1 alterations, roughly 5-7% of tumors and enriched for aggressive
  behavior - is deliberately absent from pathophysiology. Cluster 3 is a
  somatic-only molecular class with no germline predisposition gene, so it falls
  outside the hereditary axis this entry models; it belongs in a future somatic
  molecular-classification pass. The somatic ATRX/TERT aggressive-disease
  markers are, by contrast, recorded - as a modifier of the Metastatic
  Progression node rather than as their own nodes - because ATRX loss is
  specifically enriched in germline-SDHB tumors and therefore bears directly on
  the hereditary axis. (6) Penetrance figures are recorded
  from the ascertainment-adjusted analysis of Andrews et al. 2018
  (PMID:29386252) rather than the higher, widely quoted estimates from
  clinically ascertained pedigrees; see the inheritance section and the
  sdhb_penetrance_ascertainment_bias discussion for why. Per-gene penetrance for
  the non-SDHx loci (VHL, RET, NF1, SDHA, MAX, TMEM127) is not asserted because
  no comparably ascertainment-corrected source was verified for them.
references:
- reference: PMID:20301715
  title: Hereditary Paraganglioma-Pheochromocytoma Syndromes
  tags:
  - GeneReviews
  findings:
  - statement: >-
      A hereditary PGL/PCC syndrome is diagnosed by a germline heterozygous
      pathogenic variant in one of MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD or
      TMEM127 in a proband with a personal or family history of paraganglioma or
      pheochromocytoma.
    supporting_text: >-
      The diagnosis is established in a proband with a personal or family history
      of paraganglioma or pheochromocytoma and a germline heterozygous pathogenic
      variant in MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD, or TMEM127 identified by
      molecular genetic testing.
  - statement: >-
      SDHD, SDHAF2 and possibly MAX show parent-of-origin effects, causing
      disease almost exclusively on paternal transmission, with documented
      exceptions.
    supporting_text: >-
      Pathogenic variants in SDHD, SDHAF2, and possibly MAX demonstrate
      parent-of-origin effects and cause disease almost exclusively when they are
      paternally inherited
  - statement: >-
      Approximately 95% of extra-adrenal parasympathetic (head-and-neck)
      paragangliomas are nonsecretory, which is why biochemical screening alone
      cannot cover head-and-neck disease.
    supporting_text: >-
      approximately 95% of such tumors are nonsecretory
  - statement: >-
      Recommended surveillance for at-risk individuals is annual clinical
      assessment, fractionated metanephrines every two years in childhood and
      annually in adults, and whole-body MRI every two to three years.
    supporting_text: >-
      Individuals at risk for hereditary PGL/PCC syndromes should have annual
      clinical assessment for manifestations of PGL/PCCs and GISTs, plasma-free
      fractionated metanephrines or 24-hour urine fractionated metanephrines
      every two years in childhood and then annually in adults, and whole-body
      MRI every two to three years.
- reference: DOI:10.1007/s00259-023-06166-8
  title: 'Efficacy of [177Lu]Lu-DOTATATE in metastatic neuroendocrine neoplasms of different locations: data from the SEPTRALU study'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Peptide receptor radionuclide therapy (PRRT) is one of the most promising therapeutic strategies in neuroendocrine neoplasms (NENs).
    supporting_text: Peptide receptor radionuclide therapy (PRRT) is one of the most promising therapeutic strategies in neuroendocrine neoplasms (NENs).
    evidence:
    - reference: DOI:10.1007/s00259-023-06166-8
      reference_title: 'Efficacy of [177Lu]Lu-DOTATATE in metastatic neuroendocrine neoplasms of different locations: data from the SEPTRALU study'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Peptide receptor radionuclide therapy (PRRT) is one of the most promising therapeutic strategies in neuroendocrine neoplasms (NENs).
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.1007/s12020-024-03707-5
  title: 'Peptide receptor radionuclide therapy with 177Lu- or 90Y-SSTR peptides in malignant pheochromocytomas (PCCs) and paragangliomas (PGLs): results from a single institutional retrospective analysis'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: 'Peptide receptor radionuclide therapy with 177Lu- or 90Y-SSTR peptides in malignant pheochromocytomas (PCCs) and paragangliomas (PGLs): results from a single institutional retrospective analysis'
    supporting_text: 'Peptide receptor radionuclide therapy with 177Lu- or 90Y-SSTR peptides in malignant pheochromocytomas (PCCs) and paragangliomas (PGLs): results from a single institutional retrospective analysis'
- reference: DOI:10.1007/s12022-022-09746-w
  title: 'TOP2A Expression in Pheochromocytoma and Abdominal Paraganglioma: a Marker of Poor Clinical Outcome?'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Pheochromocytoma and abdominal paraganglioma (PPGL) are rare neuroendocrine tumors originating from chromaffin cells.
    supporting_text: Pheochromocytoma and abdominal paraganglioma (PPGL) are rare neuroendocrine tumors originating from chromaffin cells.
    evidence:
    - reference: DOI:10.1007/s12022-022-09746-w
      reference_title: 'TOP2A Expression in Pheochromocytoma and Abdominal Paraganglioma: a Marker of Poor Clinical Outcome?'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pheochromocytoma and abdominal paraganglioma (PPGL) are rare neuroendocrine tumors originating from chromaffin cells.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.1007/s12022-024-09830-3
  title: 'The Molecular Classification of Pheochromocytomas and Paragangliomas: Discovering the Genomic and Immune Landscape of Metastatic Disease'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Pheochromocytomas (PCCs) and paragangliomas (PGLs, together PPGLs) are the most hereditary tumors known.
    supporting_text: Pheochromocytomas (PCCs) and paragangliomas (PGLs, together PPGLs) are the most hereditary tumors known.
    evidence:
    - reference: DOI:10.1007/s12022-024-09830-3
      reference_title: 'The Molecular Classification of Pheochromocytomas and Paragangliomas: Discovering the Genomic and Immune Landscape of Metastatic Disease'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pheochromocytomas (PCCs) and paragangliomas (PGLs, together PPGLs) are the most hereditary tumors known.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.1038/s41467-023-36769-6
  title: Genomic and immune landscape Of metastatic pheochromocytoma and paraganglioma
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: The mechanisms triggering metastasis in pheochromocytoma/paraganglioma are unknown, hindering therapeutic options for patients with metastatic tumors (mPPGL).
    supporting_text: The mechanisms triggering metastasis in pheochromocytoma/paraganglioma are unknown, hindering therapeutic options for patients with metastatic tumors (mPPGL).
    evidence:
    - reference: DOI:10.1038/s41467-023-36769-6
      reference_title: Genomic and immune landscape Of metastatic pheochromocytoma and paraganglioma
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The mechanisms triggering metastasis in pheochromocytoma/paraganglioma are unknown, hindering therapeutic options for patients with metastatic tumors (mPPGL).
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.1148/rycan.210088
  title: 'Head and Neck Paragangliomas: An Update on the Molecular                     Classification, State-of-the-Art Imaging, and Management                     Recommendations'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: 'Head and Neck Paragangliomas: An Update on the Molecular                     Classification, State-of-the-Art Imaging, and Management                     Recommendations'
    supporting_text: 'Head and Neck Paragangliomas: An Update on the Molecular                     Classification, State-of-the-Art Imaging, and Management                     Recommendations'
- reference: DOI:10.1186/s13053-024-00276-6
  title: 'Current prospects of hereditary adrenal tumors: towards better clinical management'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Adrenocortical carcinoma (ACC) and pheochromocytoma/paraganglioma (PPGL) are two rare types of adrenal gland malignancies.
    supporting_text: Adrenocortical carcinoma (ACC) and pheochromocytoma/paraganglioma (PPGL) are two rare types of adrenal gland malignancies.
    evidence:
    - reference: DOI:10.1186/s13053-024-00276-6
      reference_title: 'Current prospects of hereditary adrenal tumors: towards better clinical management'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Adrenocortical carcinoma (ACC) and pheochromocytoma/paraganglioma (PPGL) are two rare types of adrenal gland malignancies.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.1186/s13550-023-01056-4
  title: '[18F]FDOPA PET/CT is superior to [68Ga]DOTATOC PET/CT in diagnostic imaging of pheochromocytoma'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Both [18F]FDOPA (FDOPA) and [68Ga]DOTATOC PET/CT (DOTATOC) are widely used for detection of pheochromocytomas/paraganglioma (PPGL).
    supporting_text: Both [18F]FDOPA (FDOPA) and [68Ga]DOTATOC PET/CT (DOTATOC) are widely used for detection of pheochromocytomas/paraganglioma (PPGL).
    evidence:
    - reference: DOI:10.1186/s13550-023-01056-4
      reference_title: '[18F]FDOPA PET/CT is superior to [68Ga]DOTATOC PET/CT in diagnostic imaging of pheochromocytoma'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Both [18F]FDOPA (FDOPA) and [68Ga]DOTATOC PET/CT (DOTATOC) are widely used for detection of pheochromocytomas/paraganglioma (PPGL).
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.1210/jendso/bvae038
  title: Patient Sex and Origin Influence Distribution of Driver Genes and Clinical Presentation of Paraganglioma
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Context Sexual and ancestral differences in driver gene prevalence have been described in many cancers but have not yet been investigated in pheochromocytoma and paraganglioma (PPGL).
    supporting_text: Context Sexual and ancestral differences in driver gene prevalence have been described in many cancers but have not yet been investigated in pheochromocytoma and paraganglioma (PPGL).
    evidence:
    - reference: DOI:10.1210/jendso/bvae038
      reference_title: Patient Sex and Origin Influence Distribution of Driver Genes and Clinical Presentation of Paraganglioma
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Context Sexual and ancestral differences in driver gene prevalence have been described in many cancers but have not yet been investigated in pheochromocytoma and paraganglioma (PPGL).
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.1590/s1677-5538.ibju.2023.0038
  title: 'The Pheochromocytoma/Paraganglioma syndrome: an overview on mechanisms, diagnosis and management'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: 'The Pheochromocytoma/Paraganglioma syndrome: an overview on mechanisms, diagnosis and management'
    supporting_text: 'The Pheochromocytoma/Paraganglioma syndrome: an overview on mechanisms, diagnosis and management'
- reference: DOI:10.3389/fendo.2023.1279828
  title: Local recurrence and metastatic disease in pheochromocytomas and sympathetic paragangliomas
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Local recurrence and metastatic disease in pheochromocytomas and sympathetic paragangliomas
    supporting_text: To evaluate the rate of recurrence among patients with pheochromocytomas and sympathetic paragangliomas (PGLs; together PPGLs) and to identify predictors of recurrence (local recurrence and/or metastatic disease).MethodsThis retrospective multicenter study included information of 303 patients with PPGLs in follow-up in 19 Spanish tertiary hospitals.
    evidence:
    - reference: DOI:10.3389/fendo.2023.1279828
      reference_title: Local recurrence and metastatic disease in pheochromocytomas and sympathetic paragangliomas
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: To evaluate the rate of recurrence among patients with pheochromocytomas and sympathetic paragangliomas (PGLs; together PPGLs) and to identify predictors of recurrence (local recurrence and/or metastatic disease).MethodsThis retrospective multicenter study included information of 303 patients with PPGLs in follow-up in 19 Spanish tertiary hospitals.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.3389/fendo.2024.1433582
  title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from chromaffin cells, with 80–85% originating in the adrenal medulla and 15–20% from extra-adrenal chromaffin tissues (paragangliomas).
    supporting_text: Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from chromaffin cells, with 80–85% originating in the adrenal medulla and 15–20% from extra-adrenal chromaffin tissues (paragangliomas).
    evidence:
    - reference: DOI:10.3389/fendo.2024.1433582
      reference_title: 'Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from chromaffin cells, with 80–85% originating in the adrenal medulla and 15–20% from extra-adrenal chromaffin tissues (paragangliomas).
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.3389/fendo.2024.1460320
  title: Prevention and management of hypertensive crises in children with pheochromocytoma and paraganglioma
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Hypertensive crises in pediatric patients are rare conditions.
    supporting_text: Hypertensive crises in pediatric patients are rare conditions.
    evidence:
    - reference: DOI:10.3389/fendo.2024.1460320
      reference_title: Prevention and management of hypertensive crises in children with pheochromocytoma and paraganglioma
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Hypertensive crises in pediatric patients are rare conditions.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.3390/biomedicines12102385
  title: 'Pheochromocytoma–Paraganglioma Syndrome: A Multiform Disease with Different Genotype and Phenotype Features'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Pheochromocytoma and paraganglioma (PPGL) are rare tumors derived from the adrenal medulla and extra-adrenal chromaffin cells.
    supporting_text: Pheochromocytoma and paraganglioma (PPGL) are rare tumors derived from the adrenal medulla and extra-adrenal chromaffin cells.
    evidence:
    - reference: DOI:10.3390/biomedicines12102385
      reference_title: 'Pheochromocytoma–Paraganglioma Syndrome: A Multiform Disease with Different Genotype and Phenotype Features'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pheochromocytoma and paraganglioma (PPGL) are rare tumors derived from the adrenal medulla and extra-adrenal chromaffin cells.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.3390/cancers15112890
  title: Long-Term Outcomes after Surgery for Pheochromocytoma and Sympathetic Paraganglioma
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: The prognosis of pheochromocytoma and sympathetic paraganglioma (PHEO/sPGL) is difficult to predict at the time of diagnosis and long-term follow-up data are scarce, especially for apparently benign and sporadic variants.
    supporting_text: The prognosis of pheochromocytoma and sympathetic paraganglioma (PHEO/sPGL) is difficult to predict at the time of diagnosis and long-term follow-up data are scarce, especially for apparently benign and sporadic variants.
    evidence:
    - reference: DOI:10.3390/cancers15112890
      reference_title: Long-Term Outcomes after Surgery for Pheochromocytoma and Sympathetic Paraganglioma
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The prognosis of pheochromocytoma and sympathetic paraganglioma (PHEO/sPGL) is difficult to predict at the time of diagnosis and long-term follow-up data are scarce, especially for apparently benign and sporadic variants.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.3390/cancers16071349
  title: 'Effects of Peptide Receptor Radiotherapy in Patients with Advanced Paraganglioma and Pheochromocytoma: A Nation-Wide Cohort Study'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Pheochromocytomas and paragangliomas are rare neuroendocrine tumours that originate from chromaffin cells within the adrenal medulla or extra-adrenal sympathetic ganglia.
    supporting_text: Pheochromocytomas and paragangliomas are rare neuroendocrine tumours that originate from chromaffin cells within the adrenal medulla or extra-adrenal sympathetic ganglia.
    evidence:
    - reference: DOI:10.3390/cancers16071349
      reference_title: 'Effects of Peptide Receptor Radiotherapy in Patients with Advanced Paraganglioma and Pheochromocytoma: A Nation-Wide Cohort Study'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Pheochromocytomas and paragangliomas are rare neuroendocrine tumours that originate from chromaffin cells within the adrenal medulla or extra-adrenal sympathetic ganglia.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.3390/jcm12041494
  title: 'Response to Peptide Receptor Radionuclide Therapy in Pheocromocytomas and Paragangliomas: A Systematic Review and Meta-Analysis'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE and 90Y-DOTATOC showed efficacy in the metastatic setting of pheocromocytomas (PCCs) and paragangliomas (PGLs) where no standard therapies have been established.
    supporting_text: Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE and 90Y-DOTATOC showed efficacy in the metastatic setting of pheocromocytomas (PCCs) and paragangliomas (PGLs) where no standard therapies have been established.
    evidence:
    - reference: DOI:10.3390/jcm12041494
      reference_title: 'Response to Peptide Receptor Radionuclide Therapy in Pheocromocytomas and Paragangliomas: A Systematic Review and Meta-Analysis'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE and 90Y-DOTATOC showed efficacy in the metastatic setting of pheocromocytomas (PCCs) and paragangliomas (PGLs) where no standard therapies have been established.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
- reference: DOI:10.37349/etat.2024.00222
  title: 'Tumor metabolism in pheochromocytomas: clinical and therapeutic implications'
  found_in:
  - Pheochromocytoma_Paraganglioma-deep-research-falcon.md
  findings:
  - statement: Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors.
    supporting_text: Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors.
    evidence:
    - reference: DOI:10.37349/etat.2024.00222
      reference_title: 'Tumor metabolism in pheochromocytomas: clinical and therapeutic implications'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors.
      explanation: Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.
datasets:
- accession: ega:EGAS00001005861
  title: Single-nuclei gene-expression analysis of pheochromocytoma and paraganglioma links tumor subtypes with tumor microenvironment
  description: Pheochromocytomas and paragangliomas (PCPG) are rare neuroendocrine tumors associated with autonomic nerves. We used single nuclei-RNA-seq (snRNA-seq) for analysis of 30 PCPG representing 13 known driver genes, plus two normal adrenal medullas to dissect cell composition, refine PCPG subtypes and compare PCPG and normal tissue expression. Incorporating bulk-tissue and snRNA-seq data we identified seven PCPG gene-expression subtypes with genotype and cell type associations.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  notes: 'European Genome-phenome Archive study, matched because the disease is named in the study''s own title ("Pheochromocytoma and Paraganglioma"); description-level mentions were not accepted. EGA study_type: Other. Controlled access -- data require a Data Access Agreement. EGA metadata retrieved 2026-08-01.'
- accession: ega:EGAS00001007844
  title: Array-based methylation analysis of SDHB-deficient pheochromocytoma and paraganglioma
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  notes: 'European Genome-phenome Archive study, matched because the disease is named in the study''s own title ("Pheochromocytoma and Paraganglioma"); description-level mentions were not accepted. EGA study_type: Cancer Genomics. Controlled access -- data require a Data Access Agreement. EGA metadata retrieved 2026-08-01.'
- accession: ega:EGAS50000000988
  title: Transcriptome analysis of 32 pheochromocytoma and paraganglioma samples
  description: Pheochromocytomas and sympathetic paragangliomas (PPGL) are rare neuroendocrine tumors derived from chromaffin tissue of the adrenal medulla and sympathetic paraganglia, respectively. There is at the moment a lack of accurate biomarkers to predict the biologic behavior of a PPGL. The aim of this study was to investigate the biological behavior of localized and metastatic PPGL by comparing the genomic and transcriptomic landscapes of localized and metastatic PPGL, including PPGL samples with a non-metastatic phenotype at initial diagnosis that developed metachronous metastases during follow-up.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  notes: 'European Genome-phenome Archive study, matched because the disease is named in the study''s own title ("Pheochromocytoma and Paraganglioma"); description-level mentions were not accepted. EGA study_type: RNASeq. Controlled access -- data require a Data Access Agreement. EGA metadata retrieved 2026-08-01.'

📚

References & Deep Research

References

PMID:20301715

Hereditary Paraganglioma-Pheochromocytoma Syndromes

4 findings

A hereditary PGL/PCC syndrome is diagnosed by a germline heterozygous pathogenic variant in one of MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD or TMEM127 in a proband with a personal or family history of paraganglioma or pheochromocytoma.

SDHD, SDHAF2 and possibly MAX show parent-of-origin effects, causing disease almost exclusively on paternal transmission, with documented exceptions.

"Pathogenic variants in SDHD, SDHAF2, and possibly MAX demonstrate parent-of-origin effects and cause disease almost exclusively when they are paternally inherited"

Approximately 95% of extra-adrenal parasympathetic (head-and-neck) paragangliomas are nonsecretory, which is why biochemical screening alone cannot cover head-and-neck disease.

"approximately 95% of such tumors are nonsecretory"

Recommended surveillance for at-risk individuals is annual clinical assessment, fractionated metanephrines every two years in childhood and annually in adults, and whole-body MRI every two to three years.

DOI:10.1007/s00259-023-06166-8

Efficacy of [177Lu]Lu-DOTATATE in metastatic neuroendocrine neoplasms of different locations: data from the SEPTRALU study

1 finding

Peptide receptor radionuclide therapy (PRRT) is one of the most promising therapeutic strategies in neuroendocrine neoplasms (NENs).

"Peptide receptor radionuclide therapy (PRRT) is one of the most promising therapeutic strategies in neuroendocrine neoplasms (NENs)."

Show evidence (1 reference)

DOI:10.1007/s00259-023-06166-8 SUPPORT Other

"Peptide receptor radionuclide therapy (PRRT) is one of the most promising therapeutic strategies in neuroendocrine neoplasms (NENs)."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.1007/s12020-024-03707-5

Peptide receptor radionuclide therapy with 177Lu- or 90Y-SSTR peptides in malignant pheochromocytomas (PCCs) and paragangliomas (PGLs): results from a single institutional retrospective analysis

1 finding

Peptide receptor radionuclide therapy with 177Lu- or 90Y-SSTR peptides in malignant pheochromocytomas (PCCs) and paragangliomas (PGLs): results from a single institutional retrospective analysis

"Peptide receptor radionuclide therapy with 177Lu- or 90Y-SSTR peptides in malignant pheochromocytomas (PCCs) and paragangliomas (PGLs): results from a single institutional retrospective analysis"

DOI:10.1007/s12022-022-09746-w

TOP2A Expression in Pheochromocytoma and Abdominal Paraganglioma: a Marker of Poor Clinical Outcome?

1 finding

Pheochromocytoma and abdominal paraganglioma (PPGL) are rare neuroendocrine tumors originating from chromaffin cells.

"Pheochromocytoma and abdominal paraganglioma (PPGL) are rare neuroendocrine tumors originating from chromaffin cells."

Show evidence (1 reference)

DOI:10.1007/s12022-022-09746-w SUPPORT Other

"Pheochromocytoma and abdominal paraganglioma (PPGL) are rare neuroendocrine tumors originating from chromaffin cells."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.1007/s12022-024-09830-3

The Molecular Classification of Pheochromocytomas and Paragangliomas: Discovering the Genomic and Immune Landscape of Metastatic Disease

1 finding

Pheochromocytomas (PCCs) and paragangliomas (PGLs, together PPGLs) are the most hereditary tumors known.

"Pheochromocytomas (PCCs) and paragangliomas (PGLs, together PPGLs) are the most hereditary tumors known."

Show evidence (1 reference)

DOI:10.1007/s12022-024-09830-3 SUPPORT Other

"Pheochromocytomas (PCCs) and paragangliomas (PGLs, together PPGLs) are the most hereditary tumors known."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.1038/s41467-023-36769-6

Genomic and immune landscape Of metastatic pheochromocytoma and paraganglioma

1 finding

The mechanisms triggering metastasis in pheochromocytoma/paraganglioma are unknown, hindering therapeutic options for patients with metastatic tumors (mPPGL).

"The mechanisms triggering metastasis in pheochromocytoma/paraganglioma are unknown, hindering therapeutic options for patients with metastatic tumors (mPPGL)."

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DOI:10.1038/s41467-023-36769-6 SUPPORT Human Clinical

"The mechanisms triggering metastasis in pheochromocytoma/paraganglioma are unknown, hindering therapeutic options for patients with metastatic tumors (mPPGL)."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.1148/rycan.210088

Head and Neck Paragangliomas: An Update on the Molecular Classification, State-of-the-Art Imaging, and Management Recommendations

1 finding

Head and Neck Paragangliomas: An Update on the Molecular Classification, State-of-the-Art Imaging, and Management Recommendations

"Head and Neck Paragangliomas: An Update on the Molecular Classification, State-of-the-Art Imaging, and Management Recommendations"

DOI:10.1186/s13053-024-00276-6

Current prospects of hereditary adrenal tumors: towards better clinical management

1 finding

Adrenocortical carcinoma (ACC) and pheochromocytoma/paraganglioma (PPGL) are two rare types of adrenal gland malignancies.

"Adrenocortical carcinoma (ACC) and pheochromocytoma/paraganglioma (PPGL) are two rare types of adrenal gland malignancies."

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DOI:10.1186/s13053-024-00276-6 SUPPORT Human Clinical

"Adrenocortical carcinoma (ACC) and pheochromocytoma/paraganglioma (PPGL) are two rare types of adrenal gland malignancies."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.1186/s13550-023-01056-4

[18F]FDOPA PET/CT is superior to [68Ga]DOTATOC PET/CT in diagnostic imaging of pheochromocytoma

1 finding

Both [18F]FDOPA (FDOPA) and [68Ga]DOTATOC PET/CT (DOTATOC) are widely used for detection of pheochromocytomas/paraganglioma (PPGL).

"Both [18F]FDOPA (FDOPA) and [68Ga]DOTATOC PET/CT (DOTATOC) are widely used for detection of pheochromocytomas/paraganglioma (PPGL)."

Show evidence (1 reference)

DOI:10.1186/s13550-023-01056-4 SUPPORT Human Clinical

"Both [18F]FDOPA (FDOPA) and [68Ga]DOTATOC PET/CT (DOTATOC) are widely used for detection of pheochromocytomas/paraganglioma (PPGL)."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.1210/jendso/bvae038

Patient Sex and Origin Influence Distribution of Driver Genes and Clinical Presentation of Paraganglioma

1 finding

Context Sexual and ancestral differences in driver gene prevalence have been described in many cancers but have not yet been investigated in pheochromocytoma and paraganglioma (PPGL).

"Context Sexual and ancestral differences in driver gene prevalence have been described in many cancers but have not yet been investigated in pheochromocytoma and paraganglioma (PPGL)."

Show evidence (1 reference)

DOI:10.1210/jendso/bvae038 SUPPORT Human Clinical

"Context Sexual and ancestral differences in driver gene prevalence have been described in many cancers but have not yet been investigated in pheochromocytoma and paraganglioma (PPGL)."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.1590/s1677-5538.ibju.2023.0038

The Pheochromocytoma/Paraganglioma syndrome: an overview on mechanisms, diagnosis and management

1 finding

The Pheochromocytoma/Paraganglioma syndrome: an overview on mechanisms, diagnosis and management

"The Pheochromocytoma/Paraganglioma syndrome: an overview on mechanisms, diagnosis and management"

DOI:10.3389/fendo.2023.1279828

Local recurrence and metastatic disease in pheochromocytomas and sympathetic paragangliomas

1 finding

Local recurrence and metastatic disease in pheochromocytomas and sympathetic paragangliomas

"To evaluate the rate of recurrence among patients with pheochromocytomas and sympathetic paragangliomas (PGLs; together PPGLs) and to identify predictors of recurrence (local recurrence and/or metastatic disease).MethodsThis retrospective multicenter study included information of 303 patients..."

Show evidence (1 reference)

DOI:10.3389/fendo.2023.1279828 SUPPORT Human Clinical

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.3389/fendo.2024.1433582

Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment

1 finding

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from chromaffin cells, with 80–85% originating in the adrenal medulla and 15–20% from extra-adrenal chromaffin tissues (paragangliomas).

"Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from chromaffin cells, with 80–85% originating in the adrenal medulla and 15–20% from extra-adrenal chromaffin tissues (paragangliomas)."

Show evidence (1 reference)

DOI:10.3389/fendo.2024.1433582 SUPPORT Human Clinical

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.3389/fendo.2024.1460320

Prevention and management of hypertensive crises in children with pheochromocytoma and paraganglioma

1 finding

Hypertensive crises in pediatric patients are rare conditions.

"Hypertensive crises in pediatric patients are rare conditions."

Show evidence (1 reference)

DOI:10.3389/fendo.2024.1460320 SUPPORT Human Clinical

"Hypertensive crises in pediatric patients are rare conditions."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.3390/biomedicines12102385

Pheochromocytoma–Paraganglioma Syndrome: A Multiform Disease with Different Genotype and Phenotype Features

1 finding

Pheochromocytoma and paraganglioma (PPGL) are rare tumors derived from the adrenal medulla and extra-adrenal chromaffin cells.

"Pheochromocytoma and paraganglioma (PPGL) are rare tumors derived from the adrenal medulla and extra-adrenal chromaffin cells."

Show evidence (1 reference)

DOI:10.3390/biomedicines12102385 SUPPORT Other

"Pheochromocytoma and paraganglioma (PPGL) are rare tumors derived from the adrenal medulla and extra-adrenal chromaffin cells."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.3390/cancers15112890

Long-Term Outcomes after Surgery for Pheochromocytoma and Sympathetic Paraganglioma

1 finding

The prognosis of pheochromocytoma and sympathetic paraganglioma (PHEO/sPGL) is difficult to predict at the time of diagnosis and long-term follow-up data are scarce, especially for apparently benign and sporadic variants.

"The prognosis of pheochromocytoma and sympathetic paraganglioma (PHEO/sPGL) is difficult to predict at the time of diagnosis and long-term follow-up data are scarce, especially for apparently benign and sporadic variants."

Show evidence (1 reference)

DOI:10.3390/cancers15112890 SUPPORT Human Clinical

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.3390/cancers16071349

Effects of Peptide Receptor Radiotherapy in Patients with Advanced Paraganglioma and Pheochromocytoma: A Nation-Wide Cohort Study

1 finding

Pheochromocytomas and paragangliomas are rare neuroendocrine tumours that originate from chromaffin cells within the adrenal medulla or extra-adrenal sympathetic ganglia.

"Pheochromocytomas and paragangliomas are rare neuroendocrine tumours that originate from chromaffin cells within the adrenal medulla or extra-adrenal sympathetic ganglia."

Show evidence (1 reference)

DOI:10.3390/cancers16071349 SUPPORT Human Clinical

"Pheochromocytomas and paragangliomas are rare neuroendocrine tumours that originate from chromaffin cells within the adrenal medulla or extra-adrenal sympathetic ganglia."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.3390/jcm12041494

Response to Peptide Receptor Radionuclide Therapy in Pheocromocytomas and Paragangliomas: A Systematic Review and Meta-Analysis

1 finding

Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE and 90Y-DOTATOC showed efficacy in the metastatic setting of pheocromocytomas (PCCs) and paragangliomas (PGLs) where no standard therapies have been established.

"Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE and 90Y-DOTATOC showed efficacy in the metastatic setting of pheocromocytomas (PCCs) and paragangliomas (PGLs) where no standard therapies have been established."

Show evidence (1 reference)

DOI:10.3390/jcm12041494 SUPPORT Other

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

DOI:10.37349/etat.2024.00222

Tumor metabolism in pheochromocytomas: clinical and therapeutic implications

1 finding

Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors.

"Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors."

Show evidence (1 reference)

DOI:10.37349/etat.2024.00222 SUPPORT Other

"Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors."

Deep research cited this publication as relevant literature for Pheochromocytoma Paraganglioma.

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Pheochromocytoma and Paraganglioma: Disease Characteristics Report

Edison Scientific Literature 32 citations 2026-08-01T01:28:42.665976

Pheochromocytoma and Paraganglioma: Disease Characteristics Report

Executive summary

Pheochromocytomas and paragangliomas (PPGLs) are rare neural-crest-derived neuroendocrine neoplasms. A pheochromocytoma (PCC) arises in adrenal-medullary chromaffin cells; a paraganglioma (PGL) arises in extra-adrenal sympathetic or parasympathetic paraganglia. Approximately 80–85% are adrenal PCCs and 15–20% are extra-adrenal PGLs. Catecholamine excess causes episodic or sustained cardiovascular and metabolic disease, while every PPGL is regarded as having some metastatic potential under current WHO classification. Germline predisposition occurs in roughly 30–40% overall and 70–80% of pediatric cases, making PPGL among the most heritable human tumors. Contemporary practice therefore combines biochemical diagnosis, molecular imaging, universal germline testing, surgery when feasible, lifelong risk-adapted surveillance, and genotype/target-informed systemic therapy. (t.2024pheochromocytomaanupdated pages 1-2, casey2024internationalconsensusstatement pages 1-2, cascon2023geneticbasesof pages 1-2)

A compact quantitative evidence summary is provided below.

Domain	High-confidence quantitative finding/recommendation	Evidence type/year	Key source DOI or PMID where available
Epidemiology / heredity	PPGLs are rare neuroendocrine tumors; ~80–85% arise in adrenal medulla and ~15–20% are extra-adrenal paragangliomas; hereditary contribution is commonly ~30–40% overall (t.2024pheochromocytomaanupdated pages 1-2, cascon2023geneticbasesof pages 1-2)	Peer-reviewed reviews, 2023–2024	10.3389/fendo.2024.1433582; 10.1530/JME-22-0167
Molecular classification	Three major molecular clusters: pseudohypoxia (cluster 1), kinase signaling (cluster 2), and Wnt-signaling / MAML3-CSDE1-associated cluster 3 (t.2024pheochromocytomaanupdated pages 1-2, cascon2023geneticbasesof pages 1-2, t.2024pheochromocytomaanupdated pages 3-6)	Peer-reviewed reviews, 2023–2024	10.3389/fendo.2024.1433582; 10.1530/JME-22-0167
Major susceptibility genes	>20 driver/susceptibility genes reported; commonly cited genes include SDHA/B/C/D, SDHAF2, VHL, RET, NF1, TMEM127, MAX, FH, MDH2, SLC25A11, DLST, EPAS1/EGLN-related genes (cascon2023geneticbasesof pages 1-2, t.2024pheochromocytomaanupdated pages 3-6)	Peer-reviewed review, 2023; scoping review, 2024	10.1530/JME-22-0167; 10.3389/fendo.2024.1433582
Phenotypes / symptom frequencies	Classic symptoms/signs are variable; one 2024 scoping review summarized hypertension 92%, sustained hypertension 48%, paroxysmal hypertension 44%, headache 59%, palpitations 50%, diaphoresis 50%, dizziness 67%, orthostatic hypotension 12% (t.2024pheochromocytomaanupdated pages 6-7)	Scoping review, 2024	10.3389/fendo.2024.1433582
Biochemical diagnosis	Plasma free metanephrines: sensitivity ~96%, specificity ~85%; suggested highly indicative thresholds in one review were normetanephrine >2.5 pmol/mL or metanephrine >1.4 pmol/mL; supine sampling after ≥30 min recumbency is recommended to reduce false positives (t.2024pheochromocytomaanupdated pages 3-6)	Scoping review, 2024	10.3389/fendo.2024.1433582
Urinary diagnosis	24-hour urinary catecholamines/metanephrines: sensitivity ~87.5%, specificity ~99.7%; urinary metanephrine/creatinine linkage can improve accuracy (t.2024pheochromocytomaanupdated pages 3-6)	Scoping review, 2024	10.3389/fendo.2024.1433582
Adjunct biochemical marker	Plasma 3-methoxytyramine is recommended with metanephrines as a first-line biochemical marker set, especially relevant for dopamine/SDH-related biology (casey2020geneticstratificationof pages 4-5)	Peer-reviewed review, 2020	10.1093/hmg/ddaa201
Clonidine suppression	For distinguishing false-positive norepinephrine elevations, clonidine suppression test reported sensitivity 97% and specificity 100%; <50% fall in plasma norepinephrine after clonidine is abnormal (t.2024pheochromocytomaanupdated pages 6-7)	Scoping review, 2024	10.3389/fendo.2024.1433582
Anatomic imaging	CT abdomen/pelvis is typical first localization test after biochemical evidence; CT sensitivity reported as 88% and accuracy 90–95% for tumors >1.3 cm in one review (t.2024pheochromocytomaanupdated pages 6-7)	Scoping review, 2024	10.3389/fendo.2024.1433582
Functional imaging detection rates	68Ga-DOTA-SST PET/CT detection ~93% (95% CI 91–95) as first-line functional imaging in one review; 18F-DOPA PET/CT ~80% (95% CI 69–88) in hereditary cluster 2; 18F-FDG PET/CT ~74% (95% CI 46–91) as alternative (t.2024pheochromocytomaanupdated pages 7-8)	Scoping review, 2024	10.3389/fendo.2024.1433582
Genotype-specific imaging guidance	SDHx-related tumors: [68Ga]-DOTA-SSA PET/CT favored; VHL- and many kinase-cluster tumors: [18F]FDOPA PET/CT often most sensitive; [123I]MIBG sensitivity ~50–75% overall and <50% in SDHB-associated tumors (giacche2024pheochromocytoma–paragangliomasyndromea pages 10-12)	Review, 2024	10.3390/biomedicines12102385
Genetic testing strategy	Germline testing is recommended for all PPGL patients; targeted NGS panels are described as current gold standard, rather than sequential gene-by-gene testing (cascon2023geneticbasesof pages 6-8, t.2024pheochromocytomaanupdated pages 7-8)	Peer-reviewed review, 2023; scoping review, 2024	10.1530/JME-22-0167; 10.3389/fendo.2024.1433582
IHC / pathology support	Loss of SDHB staining is a useful screening/prognostic biomarker for SDHx-related disease; SDHA-, MAX-, and FH-related IHC can support variant interpretation; histopathology alone cannot diagnose malignancy, which requires metastasis (casey2020geneticstratificationof pages 4-5, cascon2023geneticbasesof pages 6-8, t.2024pheochromocytomaanupdated pages 7-8)	Reviews, 2020–2024	10.1093/hmg/ddaa201; 10.1530/JME-22-0167; 10.3389/fendo.2024.1433582
Inheritance / penetrance example: SDHD	SDHD shows autosomal dominant inheritance modified by maternal imprinting; penetrance reported as 86% by age 50; tumors are mainly head-and-neck, with thoraco-abdominal PGL up to 22% and PCC 12–24% (cascon2023geneticbasesof pages 4-5)	Peer-reviewed review, 2023	10.1530/JME-22-0167
Inheritance / penetrance example: SDHB	SDHB mutations occur in ~8–10% of PPGL; penetrance reported as ~30% by age 80 in one review; associated with thoraco-abdominal PGLs, H&N PGLs, and PCCs, with higher metastatic concern (cascon2023geneticbasesof pages 2-4, cascon2023geneticbasesof pages 4-5)	Peer-reviewed review, 2023	10.1530/JME-22-0167
Inheritance / penetrance example: SDHA	SDHA pathogenic variants can be found in up to ~10% of PPGL in cited review datasets, with low penetrance estimated around 10% by age 70 and often apparently sporadic presentation (cascon2023geneticbasesof pages 4-5)	Peer-reviewed review, 2023	10.1530/JME-22-0167
Syndrome example: VHL	~20% of VHL patients develop PCC/PGL; VHL-related PPGL are often multifocal/bilateral (43–45%), metastatic in <5%, and median diagnosis age ~29 years (cascon2023geneticbasesof pages 4-5)	Peer-reviewed review, 2023	10.1530/JME-22-0167
Syndrome example: MEN2 / RET	~50% of MEN2 patients develop PCC; 50–80% of MEN2-associated PCCs are bilateral; only a small percentage metastasize (cascon2023geneticbasesof pages 5-6)	Peer-reviewed review, 2023	10.1530/JME-22-0167
Syndrome example: NF1	Estimated 0.1–5.7% of NF1 patients develop PPGL (3.3–13% in autopsy studies); NF1-associated PPGL are usually unilateral and metastasize up to ~10% (cascon2023geneticbasesof pages 5-6)	Peer-reviewed review, 2023	10.1530/JME-22-0167
Syndrome example: MAX	MAX germline review of 109 carriers reported mean diagnosis age 32.8 years, bilateral PCC in 59/101 PCC cases, metastasis in 19/101 (~18.8%), and male:female ratio 1.3:1 (OpenTargets Search: pheochromocytoma,paraganglioma)	Aggregated case series/review, 2024	10.3389/fendo.2024.1442691
Metastatic-risk markers	Independent correlates of metastatic risk reported in review include SDHB mutation plus norepinephrine/dopamine biochemical phenotype; larger size, extra-adrenal location, and cluster-1 biology are recurrent risk signals (giacche2024pheochromocytoma–paragangliomasyndromea pages 5-6, t.2024pheochromocytomaanupdated pages 7-8)	Reviews, 2024	10.3390/biomedicines12102385; 10.3389/fendo.2024.1433582
Aggressive disease biomarkers	Somatic ATRX alterations, TERT activation, and MAML3 fusions are associated with aggressive/metastatic behavior; MAML3 rearranged tumors had metastases in 37.5% in one cited review summary (casey2020geneticstratificationof pages 4-5, cascon2023geneticbasesof pages 6-8)	Reviews/pre-existing primary data synthesis	10.1093/hmg/ddaa201; 10.1530/JME-22-0167
Surgery	Minimally invasive/laparoscopic resection is generally suitable for most pheochromocytomas <5 cm; open surgery/lymph-node dissection may be preferred for larger, invasive, extra-adrenal, synchronous metastatic, or SDHB-associated tumors (t.2024pheochromocytomaanupdated pages 7-8)	Scoping review, 2024	10.3389/fendo.2024.1433582
Perioperative blockade	Endocrine Society-based preparation: alpha-blockade first; phenoxybenzamine start 10 mg orally twice daily and titrate up to 1 mg/kg/day, or doxazosin; beta-blocker added 3–4 days later if needed; increased salt/water intake 10–14 days pre-op (t.2024pheochromocytomaanupdated pages 7-8)	Scoping review/guideline-based summary, 2024	10.3389/fendo.2024.1433582
Metastatic radionuclide therapy: HSA-I-131-MIBG	FDA-approved in 2018 for metastatic PPGL; response rate ~30–40% in review summary; phase II multicenter trial of 68 patients: 25% had durable antihypertensive-medication reduction, 92% achieved partial response or stable disease within 12 months, median OS 36.7 months (95% CI 29.9–49.1) (t.2024pheochromocytomaanupdated pages 7-8)	Phase II trial summarized in 2024 review	10.3389/fendo.2024.1433582
Real-world MIBG outcome	Real-world study of 24 metastatic PPGL patients reported 38% objective response rate, 83% disease control rate, BP normalization in 56%, but notable grade 3–4 myelosuppression and one fatal pneumonitis (t.2024pheochromocytomaanupdated pages 8-9)	Real-world study summarized in review, 2024	10.3389/fendo.2024.1433582
Chemotherapy	Conventional chemotherapy response is ~37% overall in review summary; complete responses are uncommon; temozolomide may be especially relevant in SDHB/MGMT-methylated disease (t.2024pheochromocytomaanupdated pages 8-9)	Review, 2024	10.3389/fendo.2024.1433582
TKIs / targeted therapy	Sunitinib small studies showed disease control ~57–83% and median PFS ~4–13 months; FIRSTMAPP phase II reported 12-month PFS 36% on sunitinib vs 19% placebo; cabozantinib phase II ORR 25.0% (4/16 responders); axitinib phase II partial response 36% (t.2024pheochromocytomaanupdated pages 8-9)	Phase II and review summaries, 2024	10.3389/fendo.2024.1433582
Surveillance	For metastatic PPGL, CT/MRI every 3–6 months in first year, then every 6–12 months if stable; secretory disease should have plasma free or 24-h urinary fractionated metanephrines at least every 6 months (t.2024pheochromocytomaanupdated pages 7-8, taieb2023clinicalconsensusguideline pages 19-21)	Review/guideline summaries, 2023–2024	10.3389/fendo.2024.1433582; 10.1016/S2213-8587(23)00038-4
Pediatric disease	Pediatric PPGL accounts for ~10–20% of all PPGL; annual incidence ~0.5–2.0 per million children; median presentation age 11–15 years; hereditary background in ~70–80% (casey2024internationalconsensusstatement pages 1-2)	International consensus statement, 2024	10.17863/cam.111911
Pediatric metastatic management	In pediatric metastatic PPGL, surgery is the only curative therapy; about 50% of treatment-naive patients may show stable disease at 1 year; radionuclide therapy is considered for avid tumors without rapid progression (casey2024internationalconsensusstatement pages 11-13)	International consensus statement, 2024	10.17863/cam.111911
Recent single-cell findings	A 2024 preprint scRNA-seq study of 16 tissues from 5 PCC patients identified “metabolism-type” (NDUFA4L2/COX4I2) and “kinase-type” (RET/PNMT) tumors, with distinct immune microenvironments and potential therapeutic implications; this is preprint-level evidence (OpenTargets Search: pheochromocytoma,paraganglioma)	Preprint, 2024	10.1101/2023.03.26.534245
Recent multi-omics findings	A 2024 preprint multi-omic analysis of 94 SDHB-deficient tumors from 79 patients linked TERT and ATRX alterations with metastatic disease, increased mutation load, and treatment-related profiles including MGMT overexpression/MMR deficiency; preprint-level evidence (OpenTargets Search: pheochromocytoma,paraganglioma)	Preprint, 2024	10.21203/rs.3.rs-4410500/v1
Active recent trials	Examples from ClinicalTrials.gov search: NCT07714551 zanzalintinib phase II not yet recruiting (n=14); NCT07282587 ONC206 phase II recruiting (n=90); NCT03206060 Lu-177-DOTATATE phase II recruiting (n=130); NCT07680205 belzutifan impact on catecholamine metabolism phase II recruiting (n=12); NCT06429397 anlotinib + benmelstobart phase II not yet recruiting (n=22) (OpenTargets Search: pheochromocytoma,paraganglioma)	ClinicalTrials.gov records, current at retrieval	NCT07714551; NCT07282587; NCT03206060; NCT07680205; NCT06429397
Evidence gaps	Limited high-level evidence for environmental/protective factors and gene–environment interactions; limited validated QoL datasets in retrieved evidence; no robust protective genetic variants established; comparative veterinary disease/model-system evidence was not substantively captured in retrieved contexts; several omics findings are from preprints and need peer-reviewed validation (t.2024pheochromocytomaanupdated pages 8-9, cascon2023geneticbasesof pages 1-2)	Evidence-gap summary from retrieved set	10.3389/fendo.2024.1433582; 10.1530/JME-22-0167

Table: This table compiles compact, knowledge-base–ready evidence on pheochromocytoma and paraganglioma across clinical, genetic, diagnostic, and treatment domains. It prioritizes quantitative findings and recent sources, while flagging areas where evidence remains sparse or preprint-only.

1. Disease information

Definition, category, and terminology

Category: rare neuroendocrine neoplasm; neural-crest/chromaffin-cell tumor; hereditary-cancer syndrome when caused by a germline pathogenic variant.

Pheochromocytoma: adrenal-medullary PPGL.
Sympathetic PGL: usually thoracic, abdominal, or pelvic; commonly catecholamine-secreting.
Parasympathetic PGL: usually skull-base/head-and-neck, including carotid-body, vagal, jugulotympanic, and related sites; often nonsecretory.
Metastatic PPGL: tumor present in a site where normal paraganglial tissue does not occur—commonly lymph node, bone, liver, or lung. Histology alone cannot establish benignity or reliably exclude future metastasis. (casey2020geneticstratificationof pages 4-5)

Synonyms: PPGL; PCC/PGL; phaeochromocytoma/paraganglioma; chromaffinoma; adrenal paraganglioma; extra-adrenal pheochromocytoma (older term); chemodectoma or glomus tumor for selected head-and-neck PGLs.

Identifiers

MONDO: pheochromocytoma MONDO:0008233; adrenal-gland pheochromocytoma MONDO:0004974; hereditary pheochromocytoma–paraganglioma MONDO:0017366; malignant adrenal-gland pheochromocytoma MONDO:0006288. (OpenTargets Search: pheochromocytoma,paraganglioma)
OMIM syndromes: PGL1/SDHD 168000; PGL2/SDHAF2 601650; PGL3/SDHC 605373; PGL4/SDHB 115310; PGL5/SDHA 614165; PGL6/SLC25A11 618464; PGL7/DLST 618475; VHL 193300; MEN2 171400; NF1 162200. (cascon2023geneticbasesof pages 4-5, cascon2023geneticbasesof pages 5-6)
ICD-10-CM: coding is site/behavior dependent, including D35.0 (benign adrenal neoplasm), D44.6/D44.7 (uncertain behavior of carotid body, aortic body, or other paraganglia), C74.1 (malignant adrenal medulla), and C75.4/C75.5 (malignant carotid/aortic body). These behavior-based labels do not fully reflect the WHO concept that all PPGLs have variable metastatic potential.
MeSH: Pheochromocytoma and Paraganglioma are separate descriptors.

This report synthesizes aggregated disease-level resources, cohorts, trials, and guidelines, not individual EHR records. Variant interpretation for an actual patient still requires the original laboratory report, ACMG/AMP classification, phenotype, family segregation, and—where available—tumor evidence.

2. Etiology, risk, protective, and environmental factors

Causal and susceptibility factors

PPGL is fundamentally a genetic/epigenetic neoplastic disease. Approximately 40% of patients carry an autosomal-dominant germline alteration, about 30% have a recognized somatic driver, and about 30% remain unexplained by currently known genes. More than 20 susceptibility/driver genes are established or strongly implicated. (cascon2023geneticbasesof pages 1-2, cascon2023geneticbasesof pages 2-4)

Major germline causes include SDHA, SDHB, SDHC, SDHD, SDHAF2, VHL, RET, NF1, TMEM127, MAX, FH, MDH2, SLC25A11, DLST, EGLN1/2, and less frequently other metabolic-pathway genes. Important somatic/postzygotic events include NF1, VHL, RET, HRAS, FGFR1, EPAS1, H3-3A, CSDE1, and MAML3 rearrangements. Open Targets independently links PCC most strongly to MAX, TMEM127, RET, SDHB, VHL, SDHD, NF1, and SDHA. (OpenTargets Search: pheochromocytoma,paraganglioma, cascon2023geneticbasesof pages 1-2, cascon2023geneticbasesof pages 6-8)

Risk is increased by a pathogenic germline variant, family history, young age, multifocal/bilateral disease, previous PPGL, and syndromic findings such as medullary thyroid carcinoma, VHL lesions, neurofibromas/café-au-lait macules, renal-cell carcinoma, GIST, pituitary tumor, polycythemia, or uterine/cutaneous leiomyomas. SDHB alteration, extra-adrenal location, larger primary tumor, and a norepinephrine/dopamine biochemical phenotype correlate with metastatic risk. (giacche2024pheochromocytoma–paragangliomasyndromea pages 5-6, t.2024pheochromocytomaanupdated pages 7-8)

Environment and gene–environment interaction

No infectious agent, toxin, occupational exposure, diet, smoking pattern, alcohol exposure, or other modifiable environmental factor is established as a primary PPGL cause. Likewise, no replicated protective lifestyle factor or protective human allele supports primary-prevention advice beyond general cardiovascular health. Hypoxia is mechanistically relevant because cluster-1 tumors constitutively activate a hypoxia-response program, but ordinary environmental hypoxia has not been shown to cause PPGL. Pregnancy can reveal or aggravate a previously occult secretory tumor; LHCGR expression in some tumors offers a plausible hormonal mechanism. (cascon2023geneticbasesof pages 2-4, t.2024pheochromocytomaanupdated pages 3-6)

Accordingly, validated gene–environment interactions remain an evidence gap. This is absence of convincing evidence, not proof that environmental modifiers never operate.

3. Phenotypes

Phenotype	Typical character and frequency	Suggested HPO term
Hypertension	Sustained or episodic; pooled review figures: any hypertension 92%, sustained 48–55%, paroxysmal 30–45%; may cause crisis and target-organ injury	HP:0000822 Hypertension; HP:0004944 Episodic hypertension
Headache	Episodic, frequently associated with BP surges; approximately 40–59%	HP:0002315 Headache
Palpitations/tachycardia	Episodic; palpitations about 50%, tachycardia about 15%	HP:0001962 Palpitations; HP:0001649 Tachycardia
Diaphoresis/hyperhidrosis	Episodic, often accompanying crisis; approximately 50–60%	HP:0000975 Hyperhidrosis
Dizziness/syncope	Dizziness 67%, syncope approximately 40% in one synthesis	HP:0002321 Vertigo; HP:0001279 Syncope
Orthostatic hypotension	From volume contraction and receptor physiology; approximately 12%	HP:0001278 Orthostatic hypotension
Anxiety/tremor/pallor	Episodic sympathetic symptoms; anxiety approximately 19% in one synthesis	HP:0000739 Anxiety; HP:0001337 Tremor; HP:0000980 Pallor
Weight loss	Variable; approximately 30%	HP:0001824 Weight loss
Hyperglycemia/diabetes	Catecholamine-mediated inhibition of insulin secretion and altered glucose handling	HP:0003074 Hyperglycemia; HP:0000819 Diabetes mellitus
Tumor mass effects	Head-and-neck PGL: pulsatile mass, tinnitus, dysphagia, dysphonia or cranial-nerve deficits; abdominal tumors: pain/fullness	HP:0000360 Tinnitus; HP:0002015 Dysphagia; HP:0001618 Dysphonia
Laboratory abnormalities	Elevated plasma free or urinary fractionated metanephrines; dopamine-lineage tumors may elevate 3-methoxytyramine	HP:0500114 Elevated circulating catecholamine level

These frequencies are heterogeneous across referral populations and genotypes and should not be interpreted as universal penetrance estimates. Cluster-1 tumors tend to be noradrenergic/dopaminergic and may produce sustained hypertension; cluster-2 adrenal tumors more often produce epinephrine and paroxysmal attacks. Nonsecretory head-and-neck PGLs can remain clinically silent until a mass or cranial-nerve deficit develops. (giacche2024pheochromocytoma–paragangliomasyndromea pages 5-6, t.2024pheochromocytomaanupdated pages 6-7, t.2024pheochromocytomaanupdated pages 3-6)

Quality of life: attacks restrict activity, sleep, driving, employment, and social participation; chronic uncertainty, hereditary risk, repeated imaging, cranial-nerve morbidity, pain, fatigue, and treatment toxicities further impair well-being. Robust genotype-stratified EQ-5D/SF-36 estimates remain limited in the retrieved literature.

4. Genetic and molecular information

Molecular classes and causal chain

Cluster 1A—TCA-cycle/SDH pseudohypoxia: biallelic loss of SDHx, FH, MDH2, DLST, or related metabolism genes → succinate/fumarate accumulation → inhibition of α-ketoglutarate-dependent dioxygenases → HIF stabilization plus DNA/histone hypermethylation (CIMP) → angiogenesis, altered differentiation, invasion, and predominantly noradrenergic/dopaminergic secretion. SDHB tumors are particularly enriched for metastatic behavior. Suggested GO terms: tricarboxylic-acid cycle (GO:0006099), mitochondrial electron transport (GO:0006121), response to hypoxia (GO:0001666), DNA methylation (GO:0006306), angiogenesis (GO:0001525). (cascon2023geneticbasesof pages 2-4, cascon2023geneticbasesof pages 4-5, t.2024pheochromocytomaanupdated pages 3-6)
Cluster 1B—VHL/EPAS1 pseudohypoxia: impaired VHL-mediated HIF degradation or activating EPAS1/HIF-2α alteration → constitutive hypoxia transcription → vascular/metabolic tumor program. EPAS1 alterations can be postzygotic mosaic and associated with polycythemia and somatostatinoma. (cascon2023geneticbasesof pages 6-8, t.2024pheochromocytomaanupdated pages 3-6)
Cluster 2—kinase signaling: RET gain of function or loss of NF1, TMEM127, MAX and related regulators → RAS–MAPK, PI3K–AKT–mTOR, receptor-tyrosine-kinase, MYC/MAX, and translational activation → proliferation and an adrenal/adrenergic phenotype. Suggested GO: MAPK cascade (GO:0000165), PI3K signaling (GO:0014065), TOR signaling (GO:0031929), cell proliferation (GO:0008283). (cascon2023geneticbasesof pages 2-4, cascon2023geneticbasesof pages 5-6)
Cluster 3—WNT altered: somatic MAML3–UBTF fusions or CSDE1 alterations → WNT/β-catenin and developmental transcriptional dysregulation → proliferation, angiogenesis, and invasion. MAML3 rearrangements represented 5–7% in one synthesis; 37.5% of fusion-positive tumors developed metastases in the cited series. (cascon2023geneticbasesof pages 1-2, cascon2023geneticbasesof pages 6-8)

Variant interpretation

Pathogenic alterations include missense, nonsense, frameshift, splice, copy-number, deletion, loss-of-heterozygosity, fusion, promoter/epigenetic, and postzygotic mosaic events. Tumor-suppressor genes generally operate through loss of function and a somatic second hit; RET and EPAS1 commonly act through gain of function. Population frequency alone is insufficient, especially for low-penetrance SDHA variants. VUS must not direct predictive testing or irreversible management. Tumor LOH, metabolomics, and IHC—loss of SDHB/SDHA/MAX or positive 2-succinocysteine in FH-deficient disease—can supply functional evidence. (cascon2023geneticbasesof pages 6-8, cascon2023geneticbasesof pages 4-5)

Penetrance and genotype–phenotype examples

SDHD: autosomal dominant with parent-of-origin effect, usually disease after paternal transmission; reported penetrance 86% by age 50; predominantly head-and-neck PGL.
SDHB: autosomal dominant, incomplete age-dependent penetrance—approximately 30% by age 80 in one synthesis; often a solitary thoracoabdominal PGL without family history; substantial metastatic concern.
SDHA: low penetrance, approximately 10% by age 70; many probands appear sporadic.
VHL: approximately 20% develop PPGL; 43–45% multifocal/bilateral, <5% metastatic, median diagnosis around 29 years.
RET/MEN2: approximately 50% lifetime PCC risk; 50–80% bilateral; metastatic disease uncommon.
NF1: clinically recognized PPGL in approximately 0.1–5.7%, higher in autopsy series; usually unilateral adrenal tumors.
MAX: preferential paternal transmission has been reported. A 2024 aggregation of 109 carriers found 101 PCC cases, 59 bilateral tumors, 18.8% metastasis, and mean diagnosis age 32.8 years. (cascon2023geneticbasesof pages 4-5, cascon2023geneticbasesof pages 5-6)

No repeat expansion is implicated. Routine karyotyping and FISH are not first-line tests; chromosomal microarray may detect large deletions but is less efficient than a sequencing panel that includes deletion/duplication analysis. Mitochondrial nuclear genes are central, but mitochondrial-DNA testing is not routine.

Recent single-cell and multi-omics research

A 2024 single-cell preprint analyzed 133,894 cells from 16 tissues in five PCC patients and proposed metabolism-type tumors marked by NDUFA4L2/COX4I2 and kinase-type tumors marked by RET/PNMT, with distinct FGF, annexin, inflammatory, HLA-I, and T-cell microenvironments. This is hypothesis-generating because of the very small patient sample and preprint status. A separate 2024 preprint integrating seven assays in 94 SDHB-deficient tumors from 79 patients associated TERT/ATRX alterations with metastasis and identified MGMT overexpression and mismatch-repair deficiency as possible alkylator-resistance mechanisms. (OpenTargets Search: pheochromocytoma,paraganglioma)

A concise quote from the 2023 genetics review captures the field: “there are currently more than 20 driver genes implicated in either the hereditary or the sporadic nature of the disease.” It further reports that genetic diagnosis is achieved in approximately 75–80%. Published April 2023; DOI. (cascon2023geneticbasesof pages 1-2)

5. Environmental information

There is no established infectious etiology and no evidence supporting vaccination, antimicrobial prophylaxis, toxin avoidance, or a specific diet as PPGL prevention. Exercise, caffeine, nicotine, sympathomimetics, stress, anesthesia, tumor manipulation, and selected drugs can trigger symptoms or interfere with biochemical testing, but are not proven tumor initiators. Pregnancy is a clinically important physiologic context because catecholamine excess threatens both mother and fetus; early recognition and alpha blockade improve outcomes. (t.2024pheochromocytomaanupdated pages 6-7, t.2024pheochromocytomaanupdated pages 3-6)

6. Pathophysiology

The clinical causal chain is:

driver alteration/second hit → chromaffin or paraganglial-cell transformation → cluster-specific metabolic or kinase program → tumor growth ± catecholamine synthesis → α-adrenergic vasoconstriction, β-adrenergic chronotropy/inotropy, volume contraction, insulin suppression and lipolysis → hypertension, headache, sweating, palpitations, arrhythmia, cardiomyopathy, hyperglycemia and crisis. Chronic or extreme catecholamine exposure can produce myocarditis/cardiomyopathy, stroke, pulmonary edema, intestinal ischemia/ileus, and acute kidney injury. (t.2024pheochromocytomaanupdated pages 6-7, t.2024pheochromocytomaanupdated pages 3-6)

Relevant cells include adrenal chromaffin cells (CL:0000166), sympathetic neurons (CL:0000095), sustentacular cells, endothelial cells (CL:0000115), fibroblasts (CL:0000057), macrophages (CL:0000235), and lymphocytes. Relevant compartments are mitochondrion (GO:0005739), mitochondrial respiratory-chain complex II (GO:0005749), nucleus (GO:0005634), and cytosol (GO:0005829). Immune-checkpoint therapy has shown limited activity to date; low CD8 infiltration and genotype-dependent antigen-presentation programs may contribute, but the immune landscape remains investigational.

7. Anatomical structures affected

Primary sites are adrenal medulla (UBERON:0001235), sympathetic chain/paraganglia, organ of Zuckerkandl, retroperitoneum, mediastinum, urinary bladder, pelvis, carotid body, vagal body, jugulotympanic region, and skull base. Sympathetic tumors are generally secretory; parasympathetic head-and-neck tumors are often nonsecretory. Hereditary disease is more often bilateral or multifocal. (t.2024pheochromocytomaanupdated pages 1-2, cascon2023geneticbasesof pages 2-4)

Secondary injury involves cardiovascular, cerebrovascular, renal, pulmonary, gastrointestinal, endocrine/metabolic, and peripheral/cranial nervous systems. Metastatic targets are especially lymph node, bone, liver, and lung. In an aggregation of 107 SDHA-associated cases, tumors were head-and-neck in 46% and abdominal in 43%; among metastatic cases, bone and lymph nodes were involved in 82% and 71%, respectively. (t.2024pheochromocytomaanupdated pages 1-2)

8. Temporal development

Most sporadic diagnoses occur at age 30–50, with similar sex distribution. Pediatric PPGL represents approximately 10–20% of all PPGL, has annual incidence around 0.5–2 per million children, and presents at median age 11–15. Childhood disease is hereditary in 70–80%. (t.2024pheochromocytomaanupdated pages 1-2, casey2024internationalconsensusstatement pages 1-2)

The course ranges from an incidental stable mass to episodic catecholamine attacks, acute crisis, slowly progressive multifocal disease, or aggressive metastasis. Recurrence/metastasis can emerge decades after apparently complete resection; therefore “five-year cure” is unsafe for high-risk genotypes. Approximately half of treatment-naïve metastatic pediatric patients may remain stable at one year, illustrating that immediate systemic treatment is not obligatory for every asymptomatic patient. (casey2024internationalconsensusstatement pages 11-13)

9. Inheritance and population epidemiology

PPGL is rare; precise incidence varies with case ascertainment and incidental imaging. It accounts for roughly 0.1% of hypertension in the 2024 synthesis. About 35–45% harbor a germline pathogenic variant, including 10–12% of apparently sporadic presentations. The usual pattern is autosomal dominant with incomplete, age-dependent, gene-specific penetrance; SDHD, SDHAF2, and sometimes MAX show parent-of-origin effects. De novo and postzygotic mosaic disease occur, notably in VHL, EPAS1, H3-3A, and NF1. (t.2024pheochromocytomaanupdated pages 1-2, giacche2024pheochromocytoma–paragangliomasyndromea pages 5-6, cascon2023geneticbasesof pages 6-8)

No consistent overall sex bias is established. Founder variants exist in particular populations, but population-specific carrier frequency cannot be safely inferred from unselected gnomAD frequency because penetrance differs sharply by gene and variant. Consanguinity is not a major general risk factor for these predominantly dominant syndromes.

10. Diagnostics

Biochemistry

First-line testing is plasma free metanephrines or 24-hour urinary fractionated metanephrines, preferably measured by LC–MS/MS. Plasma sampling should occur after at least 20–30 minutes supine rest. A 2024 synthesis reported plasma sensitivity 96% and specificity 85%, and urinary sensitivity 87.5% and specificity 99.7%, although performance varies by assay and referral setting. Plasma 3-methoxytyramine improves detection of dopamine-producing and SDHx-related disease. Exercise, acute illness, stress, posture, tricyclics, MAO inhibitors, sympathomimetics, selected antipsychotics, and analytical interference can cause false positives. Borderline normetanephrine elevation may be evaluated with clonidine suppression after correcting confounders. (casey2020geneticstratificationof pages 4-5, t.2024pheochromocytomaanupdated pages 6-7, t.2024pheochromocytomaanupdated pages 3-6)

Localization and staging

After biochemical confirmation, contrast CT of abdomen/pelvis is a usual first localization study; MRI is preferred in children, pregnancy, head-and-neck disease, and repeated hereditary surveillance. One review reported CT sensitivity of 88% and 90–95% localization accuracy for tumors >1.3 cm. (t.2024pheochromocytomaanupdated pages 6-7)

Functional imaging should be selected by genotype and therapeutic question:

^68Ga-DOTATATE/DOTA-SSA PET/CT: favored for SDHx, multifocal, metastatic, and head-and-neck disease; pooled detection approximately 93%.
^18F-FDOPA PET/CT: strong performance in VHL and cluster-2 adrenal disease; detection about 80% in one synthesis.
^18F-FDG PET/CT: useful for aggressive, dedifferentiated, and SDHB-associated disease; reported detection about 74%.
^123I-MIBG: principally to establish eligibility for ^131I-MIBG therapy; sensitivity 50–75% overall and <50% in SDHB-associated disease. (giacche2024pheochromocytoma–paragangliomasyndromea pages 10-12, t.2024pheochromocytomaanupdated pages 7-8, t.2024pheochromocytomaanupdated pages 8-9)

Pathology and genetics

Histology typically shows nests/trabeculae (“zellballen”) of granular neuroendocrine cells with sustentacular cells. Useful markers include chromogranin A, synaptophysin, INSM1, GATA3, tyrosine hydroxylase, and sustentacular S100/SOX10. Cytokeratin is usually absent or focal. SDHB loss screens for SDH deficiency; combined SDHA loss points toward SDHA. FH/2SC and MAX staining can guide genotype. PASS and GAPP provide risk stratification but cannot prove benignity or reliably predict an individual outcome. (casey2020geneticstratificationof pages 4-5, t.2024pheochromocytomaanupdated pages 7-8, t.2024pheochromocytomaanupdated pages 3-6)

All patients should be offered pre-test counseling and a germline multigene NGS panel with deletion/duplication detection. A practical panel includes SDHA/B/C/D, SDHAF2, VHL, RET, NF1, TMEM127, MAX, FH, MDH2, SLC25A11, DLST and other validated laboratory genes. If germline testing is negative, paired tumor-normal sequencing can identify somatic drivers and mosaicism. Combined analysis detects a driver in approximately 75–80%. VUS must not trigger cascade testing. (cascon2023geneticbasesof pages 1-2, casey2020geneticstratificationof pages 4-5, cascon2023geneticbasesof pages 6-8)

Differential diagnosis

Differentials include essential hypertension, panic disorder, hyperthyroidism, hypoglycemia, carcinoid syndrome, mast-cell activation, obstructive sleep apnea, medication/drug withdrawal, baroreflex failure, pseudopheochromocytoma, neuroblastoma, adrenal cortical adenoma/carcinoma, renal-cell carcinoma, schwannoma, and other neuroendocrine tumors. Biochemical metanephrine patterns, imaging location, and pathology resolve most cases.

11. Outcome and prognosis

Localized completely resected disease often has excellent long-term survival, but recurrence remains possible. Metastasis occurs in a minority—approximately 10–30% across heterogeneous series—and is more likely with SDHB/FH biology, extra-adrenal primary, larger tumor, dopamine/3-methoxytyramine production, high burden, and TERT/ATRX/MAML3 alterations. No single histologic or molecular marker is sufficiently accurate; expert reviews favor composite clinical, biochemical, imaging, pathological, and genomic assessment. (t.2024pheochromocytomaanupdated pages 1-2, giacche2024pheochromocytoma–paragangliomasyndromea pages 5-6, casey2020geneticstratificationof pages 4-5)

Morbidity reflects catecholamine-mediated cardiovascular injury, treatment toxicity, cranial-nerve deficits after head-and-neck intervention, metastatic pain/fracture, renal dysfunction, and lifelong surveillance burden. The precise median survival of metastatic disease is highly variable and should not be represented by one pooled number. In the pivotal high-specific-activity ^131I-MIBG cohort, median overall survival was 36.7 months, but that selected treatment population is not equivalent to all metastatic PPGL. (t.2024pheochromocytomaanupdated pages 7-8)

12. Treatment

Localized disease

Surgical excision is the only established curative treatment. Minimally invasive adrenalectomy is generally used for localized PCC under approximately 5–6 cm; open resection is favored for invasion, large/fragile tumors, selected SDHB-related PGLs, or when en-bloc resection and nodal dissection are required. Cortical-sparing adrenalectomy can preserve steroid function in selected bilateral hereditary PCC. Head-and-neck management may use observation, surgery, or radiotherapy according to growth, symptoms, cranial-nerve risk, age, and genotype. (t.2024pheochromocytomaanupdated pages 7-8)

Secretory tumors require preoperative alpha blockade first—phenoxybenzamine or a selective α1 antagonist such as doxazosin—plus salt/fluid repletion. A beta blocker may be added only after adequate alpha blockade for tachycardia; unopposed beta blockade can precipitate crisis. One guideline-based regimen starts phenoxybenzamine 10 mg twice daily, titrating up to 1 mg/kg/day, with beta blockade added 3–4 days later. Suggested NCIt concepts include adrenalectomy, tumor resection, phenoxybenzamine, doxazosin, and beta-adrenergic blockade. (t.2024pheochromocytomaanupdated pages 7-8)

Metastatic/unresectable disease

Observation/local control: appropriate for asymptomatic, low-volume, stable disease. Surgery, ablation, embolization, external-beam or stereotactic radiotherapy, and cementoplasty can address oligometastases, pain, impending fracture, compression, or hormone burden.
High-specific-activity ^131I-MIBG: FDA-approved in 2018 for MIBG-avid advanced PPGL. In 68 treated patients, 25% had durable antihypertensive-medication reduction, 92% had partial response or stable disease within 12 months, and median OS was 36.7 months; nausea, fatigue, and myelosuppression were common. (t.2024pheochromocytomaanupdated pages 7-8)
^177Lu-DOTATATE PRRT: used for strongly somatostatin-receptor-positive disease; current PPGL evidence is largely retrospective, with prospective phase II evaluation ongoing. (taieb2023clinicalconsensusguideline pages 19-21, t.2024pheochromocytomaanupdated pages 8-9)
CVD chemotherapy: cyclophosphamide–vincristine–dacarbazine for rapidly progressive/high-burden disease; aggregated response approximately 37%, with complete responses uncommon.
Temozolomide: oral alkylator, particularly rational in SDHB-deficient/MGMT-silenced disease; acquired MGMT expression or mismatch-repair defects may cause resistance. (t.2024pheochromocytomaanupdated pages 8-9)
Sunitinib: FIRSTMAPP demonstrated 12-month progression-free survival in 36% versus 19% with placebo; grade 3–4 toxicities included asthenia and hypertension.
Cabozantinib: Natalie phase II trial objective response 25% (4/16 evaluable patients).
Axitinib: phase II partial response approximately 36% in the cited synthesis.
Immunotherapy: not standard; response evidence remains limited. (t.2024pheochromocytomaanupdated pages 8-9)

Pharmacogenomic treatment selection currently reflects tumor biology more than host drug-metabolism genotype: MIBG/SLC6A2 avidity, SSTR expression, SDHB/MGMT status, VEGF-driven pseudohypoxia, and VHL/HIF-2α biology.

Trials and recent development

Retrieved ClinicalTrials.gov examples include NCT03206060, phase II ^177Lu-DOTATATE, recruiting, target n=130; NCT04394858, temozolomide±olaparib, active/not recruiting, n=46; NCT05636540, ^18F-fluorThanatrace PARP-1 PET, recruiting, n=30; NCT03946527, lanreotide, active/not recruiting, n=10; and NCT06429397, anlotinib plus benmelstobart, phase II, not yet recruiting, n=22. Trial status changes over time and should be rechecked before clinical use.

13. Prevention

There is no vaccine or proven population-level primary prevention. The effective prevention strategy is secondary and tertiary prevention:

universal germline testing of affected patients;
cascade testing of relatives only for pathogenic/likely pathogenic actionable variants;
lifelong gene-specific biochemical and MRI surveillance;
recognition and treatment before pregnancy or elective surgery;
perioperative alpha blockade to prevent crisis;
prompt management of hypertension, arrhythmia, cardiomyopathy, diabetes, and skeletal metastases. (casey2024internationalconsensusstatement pages 11-13, taieb2023clinicalconsensusguideline pages 19-21, t.2024pheochromocytomaanupdated pages 7-8)

For SDHD carriers, expert consensus recommends annual plasma metanephrines and whole-body MRI every 2–3 years; other genes use age- and risk-adapted intervals. Reproductive counseling may include prenatal or preimplantation genetic testing after a familial pathogenic variant is established. Population newborn screening is not indicated.

14. Other species and natural disease

Naturally occurring PCC/PGL occurs in companion and laboratory animals, especially dogs, cattle, and rats, but the retrieved evidence did not support reliable breed-specific incidence or VBO mappings. These tumors are not infectious or zoonotic and have no cross-species transmission. Orthologues of SDHx, VHL, RET, NF1, TMEM127, MAX, FH, and EPAS1 are broadly conserved, making comparative pathology biologically relevant. Veterinary PCC commonly resembles human chromaffin neuroendocrine morphology and catecholamine biology, but species-specific natural history limits direct therapeutic extrapolation.

Suggested taxonomy identifiers are Homo sapiens NCBI:9606, Mus musculus NCBI:10090, Rattus norvegicus NCBI:10116, Canis lupus familiaris NCBI:9615, and Bos taurus NCBI:9913.

15. Model organisms and experimental systems

Common models include rat PC12 pheochromocytoma cells, mouse MPC cells and metastatic derivatives, human PPGL primary cultures, patient-derived xenografts, organoids/spheroids, SDHB/SDHD knockdown systems, and genetically engineered mice affecting Nf1, Ret, Vhl, Sdh genes, Hif2a/Epas1, or Myc pathways. Three-dimensional cultures better model gradients, extracellular matrix, and drug penetration than conventional monolayers. (OpenTargets Search: pheochromocytoma,paraganglioma)

Major limitations are difficulty maintaining differentiated human chromaffin cells, incomplete spontaneous metastasis, species-specific catecholamine biology, and failure of many single-gene mouse models to reproduce the complete human syndrome. Current best practice uses complementary systems: human tumor multi-omics for discovery; isogenic cell models for mechanism; 3-D cultures for microenvironment/drug screening; and xenograft or engineered-animal models for pharmacology and dissemination.

Evidence appraisal and authoritative interpretation

The 2024 WHO-oriented molecular review emphasizes that all PPGLs are neoplasms with variable metastatic potential and that “no single biomarker alone can reliably predict metastatic risk.” Published October 2024; DOI. (t.2024pheochromocytomaanupdated pages 1-2)

The 2024 pediatric consensus—developed by 43 international experts—places germline testing, multidisciplinary care, genotype-adapted imaging, and lifelong surveillance at the center of management. Published September 2024; DOI. (casey2024internationalconsensusstatement pages 1-2, casey2024internationalconsensusstatement pages 11-13)

The clearest 2023–2024 advances are: broader universal paired germline/tumor sequencing; genotype-specific PET selection; prospective evidence for antiangiogenic TKIs; expansion of SSTR-directed theranostics; HIF-2α and DNA-repair-directed trials; and single-cell/multi-omics identification of microenvironment and resistance states. However, most treatment studies remain small because PPGL is rare, and several advanced-omics results are still preprints. (cascon2023geneticbasesof pages 1-2, t.2024pheochromocytomaanupdated pages 8-9)

Principal sources: Cascón et al., Journal of Molecular Endocrinology, April 2023, DOI 10.1530/JME-22-0167; Taïeb et al., Lancet Diabetes & Endocrinology, May 2023, DOI 10.1016/S2213-8587(23)00038-4; Casey et al., Nature Reviews Endocrinology, September 2024, DOI 10.1038/s41574-024-01024-5; Giacché et al., October 2024, DOI 10.3390/biomedicines12102385; Saavedra et al., Frontiers in Endocrinology, December 13, 2024, DOI 10.3389/fendo.2024.1433582.

References

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(t.2024pheochromocytomaanupdated pages 6-7): J. S. Saavedra T., Humberto Alejandro Nati-Castillo, L. A. Valderrama Cometa, Wilfredo A. Rivera-Martínez, Josué Asprilla, C. M. Castaño-Giraldo, Leonardo Sánchez S., Mishell Heredia-Espín, Marlon Arias-Intriago, and Juan S. Izquierdo-Condoy. Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment. Frontiers in Endocrinology, Dec 2024. URL: https://doi.org/10.3389/fendo.2024.1433582, doi:10.3389/fendo.2024.1433582. This article has 47 citations.
(casey2020geneticstratificationof pages 4-5): Ruth Casey, Hartmut PH Neumann, and Eamonn R Maher. Genetic stratification of inherited and sporadic phaeochromocytoma and paraganglioma: implications for precision medicine. Human molecular genetics, Oct 2020. URL: https://doi.org/10.1093/hmg/ddaa201, doi:10.1093/hmg/ddaa201. This article has 38 citations and is from a domain leading peer-reviewed journal.
(t.2024pheochromocytomaanupdated pages 7-8): J. S. Saavedra T., Humberto Alejandro Nati-Castillo, L. A. Valderrama Cometa, Wilfredo A. Rivera-Martínez, Josué Asprilla, C. M. Castaño-Giraldo, Leonardo Sánchez S., Mishell Heredia-Espín, Marlon Arias-Intriago, and Juan S. Izquierdo-Condoy. Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment. Frontiers in Endocrinology, Dec 2024. URL: https://doi.org/10.3389/fendo.2024.1433582, doi:10.3389/fendo.2024.1433582. This article has 47 citations.
(giacche2024pheochromocytoma–paragangliomasyndromea pages 10-12): Mara Giacché, Maria Chiara Tacchetti, Claudia Agabiti-Rosei, Francesco Torlone, Francesco Bandera, Claudia Izzi, and Enrico Agabiti-Rosei. Pheochromocytoma–paraganglioma syndrome: a multiform disease with different genotype and phenotype features. Oct 2024. URL: https://doi.org/10.3390/biomedicines12102385, doi:10.3390/biomedicines12102385. This article has 10 citations.
(cascon2023geneticbasesof pages 6-8): Alberto Cascón, Bruna Calsina, María Monteagudo, Sara Mellid, Alberto Díaz-Talavera, Maria Currás-Freixes, and Mercedes Robledo. Genetic bases of pheochromocytoma and paraganglioma. Journal of Molecular Endocrinology, Apr 2023. URL: https://doi.org/10.1530/jme-22-0167, doi:10.1530/jme-22-0167. This article has 92 citations and is from a peer-reviewed journal.
(cascon2023geneticbasesof pages 4-5): Alberto Cascón, Bruna Calsina, María Monteagudo, Sara Mellid, Alberto Díaz-Talavera, Maria Currás-Freixes, and Mercedes Robledo. Genetic bases of pheochromocytoma and paraganglioma. Journal of Molecular Endocrinology, Apr 2023. URL: https://doi.org/10.1530/jme-22-0167, doi:10.1530/jme-22-0167. This article has 92 citations and is from a peer-reviewed journal.
(cascon2023geneticbasesof pages 2-4): Alberto Cascón, Bruna Calsina, María Monteagudo, Sara Mellid, Alberto Díaz-Talavera, Maria Currás-Freixes, and Mercedes Robledo. Genetic bases of pheochromocytoma and paraganglioma. Journal of Molecular Endocrinology, Apr 2023. URL: https://doi.org/10.1530/jme-22-0167, doi:10.1530/jme-22-0167. This article has 92 citations and is from a peer-reviewed journal.
(cascon2023geneticbasesof pages 5-6): Alberto Cascón, Bruna Calsina, María Monteagudo, Sara Mellid, Alberto Díaz-Talavera, Maria Currás-Freixes, and Mercedes Robledo. Genetic bases of pheochromocytoma and paraganglioma. Journal of Molecular Endocrinology, Apr 2023. URL: https://doi.org/10.1530/jme-22-0167, doi:10.1530/jme-22-0167. This article has 92 citations and is from a peer-reviewed journal.
(OpenTargets Search: pheochromocytoma,paraganglioma): Open Targets Query (pheochromocytoma,paraganglioma, 32 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(giacche2024pheochromocytoma–paragangliomasyndromea pages 5-6): Mara Giacché, Maria Chiara Tacchetti, Claudia Agabiti-Rosei, Francesco Torlone, Francesco Bandera, Claudia Izzi, and Enrico Agabiti-Rosei. Pheochromocytoma–paraganglioma syndrome: a multiform disease with different genotype and phenotype features. Oct 2024. URL: https://doi.org/10.3390/biomedicines12102385, doi:10.3390/biomedicines12102385. This article has 10 citations.
(t.2024pheochromocytomaanupdated pages 8-9): J. S. Saavedra T., Humberto Alejandro Nati-Castillo, L. A. Valderrama Cometa, Wilfredo A. Rivera-Martínez, Josué Asprilla, C. M. Castaño-Giraldo, Leonardo Sánchez S., Mishell Heredia-Espín, Marlon Arias-Intriago, and Juan S. Izquierdo-Condoy. Pheochromocytoma: an updated scoping review from clinical presentation to management and treatment. Frontiers in Endocrinology, Dec 2024. URL: https://doi.org/10.3389/fendo.2024.1433582, doi:10.3389/fendo.2024.1433582. This article has 47 citations.
(taieb2023clinicalconsensusguideline pages 19-21): David Taïeb, George B Wanna, Maleeha Ahmad, Charlotte Lussey-Lepoutre, Nancy D Perrier, Svenja Nölting, Laurence Amar, Henri J L M Timmers, Zachary G Schwam, Anthony L Estrera, Michael Lim, Erqi Liu Pollom, Lucas Vitzthum, Isabelle Bourdeau, Ruth T Casey, Frédéric Castinetti, Roderick Clifton-Bligh, Eleonora P M Corssmit, Ronald R de Krijger, Jaydira Del Rivero, Graeme Eisenhofer, Hans K Ghayee, Anne-Paule Gimenez-Roqueplo, Ashley Grossman, Alessio Imperiale, Jeroen C Jansen, Abhishek Jha, Michiel N Kerstens, Henricus P M Kunst, James K Liu, Eamonn R Maher, Daniele Marchioni, Leilani B Mercado-Asis, Ozgur Mete, Mitsuhide Naruse, Naris Nilubol, Neeta Pandit-Taskar, Frédéric Sebag, Akiyo Tanabe, Jiri Widimsky, Leah Meuter, Jacques W M Lenders, and Karel Pacak. Clinical consensus guideline on the management of phaeochromocytoma and paraganglioma in patients harbouring germline sdhd pathogenic variants. May 2023. URL: https://doi.org/10.1016/s2213-8587(23)00038-4, doi:10.1016/s2213-8587(23)00038-4. This article has 113 citations and is from a highest quality peer-reviewed journal.
(casey2024internationalconsensusstatement pages 11-13): Ruth T Casey, Emile Hendriks, Cheri Deal, Steven G Waguespack, Verena Wiegering, Antje Redlich, Scott Akker, Rathi Prasad, Martin Fassnacht, Roderick Clifton-Bligh, Laurence Amar, Stefan Bornstein, Letizia Canu, Evangelia Charmandari, Alexandra Chrisoulidou, Maria Currás Freixes, Ronald De Krijger, Luisa De Sanctis, Antonio Fojo, Amol J Ghia, Angela Huebner, Vasilis Kosmoliaptsis, Michaela Kuhlen, Marco Raffaelli, Charlotte Lussey-Lepoutre, Stephen D Marks, Naris Nilubol, Mirko Parasiliti-Caprino, Henri HJLM Timmers, Anna Lena Zietlow, Mercedes Robledo, Anne-Paule Gimenez-Roqueplo, Ashley B Grossman, David Taïeb, Eamonn R Maher, Jacques WM Lenders, Graeme Eisenhofer, Camilo Jimenez, Karel Pacak, and Christina Pamporaki. International consensus statement on the diagnosis and management of phaeochromocytoma and paraganglioma in children and adolescents. JournalArticle, Sep 2024. URL: https://doi.org/10.17863/cam.111911, doi:10.17863/cam.111911. This article has 69 citations.

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Pheochromocytoma and Paraganglioma: Disease Characteristics Report

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2. Etiology, risk, protective, and environmental factors

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Environment and gene–environment interaction

3. Phenotypes

4. Genetic and molecular information

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5. Environmental information

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7. Anatomical structures affected

8. Temporal development

9. Inheritance and population epidemiology

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Localization and staging

Pathology and genetics

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11. Outcome and prognosis

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