Pseudomyxoma Peritonei

Neoplastic MONDO:0017048 Pathograph 17 Show in embeddings browser Appendiceal Mucinous Neoplasm Peritoneal Surface Malignancy

A rare peritoneal syndrome in which a mucinous neoplasm - almost always of the appendix - perforates and redistributes mucin-secreting epithelium across the peritoneal surfaces, which then accumulate mucin progressively until abdominal organs are mechanically compromised. Incidence is around 3.2 per million per year. Three things distinguish it from the way solid tumours usually behave, and the entry is built around them. The lethal agent is a secreted product, not the cells. Patients are killed by mucin. Tumour cell burden can be modest while litres of mucus accumulate, stiffen, and encase the viscera; the mucus sclerosis is described in the primary literature as the key pathological mechanism and the main cause of death. Curating this as a disease of hypersecretion rather than of proliferation is the entry's organising decision. Its driver genetics are unusually clean and unusually consistent. KRAS and GNAS are mutated in the large majority of cases - 89% and 83% respectively in the largest systematically sequenced series - and the pair co-occurs far more often than chance. The GNAS arm is mechanistically pointed: constitutive Gs-cAMP signalling is a recognised driver of mucin hypersecretion, so the second driver acts on precisely the process that makes the disease lethal. It spreads by fluid mechanics rather than by invasion. Cells are carried on peritoneal fluid currents and settle where the fluid is resorbed or pools, which is why omentum, paracolic gutters and ovaries are involved while the bowel serosa is often spared. That is also why the treatment is a surgical and regional-chemotherapy problem rather than a systemic one.

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Pathophys.
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Histopath.
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Phenotypes
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Gaps
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Pathograph
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Genes
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Medical Actions
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Trials
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Models
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References
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Deep Research
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Discussions and Knowledge Gaps

3
In the PDX model, does the murine origin of the inflammatory signal limit what can be concluded about the human peritoneal microenvironment that drives fibrosis and sclerosis?
HUMAN MODEL MISMATCH OPEN mismatch_pdx_stromal_species
Attached to
animal_models#Mouse pathophysiology#Progressive Intraperitoneal Mucin Accumulation and Sclerosis
This is not a case of absent evidence - the model exists and reproduces both the histopathology and an elevated ascites cytokine profile. The open question is what that evidence licenses. The cytokines were secreted mostly by mouse-derived stromal cells rather than by human tumour cells, and IL-6 and IL-8/KC/MIP2 differed significantly between human and PDX ascites. So the model demonstrates that human PMP tumour cells can provoke an inflammatory stromal response, and lets that response be attributed to stroma by species. It does not establish that the human stromal response has the same composition. Because this entry treats mucin accumulation with sclerosis as the node that produces clinical harm, and fibrosis is stroma-driven, the gap sits directly under a load-bearing claim.
Proposed experiments
Species-resolved cytokine profiling of human versus PDX PMP ascites
compare_human_pdx_stromal_cytokines
Paired profiling of human PMP ascites and matched PDX ascites with species-resolved assignment of each cytokine to human tumour or murine stromal origin, to quantify which components of the human inflammatory milieu the model reproduces and which it replaces.
Would support
pathophysiology#Progressive Intraperitoneal Mucin Accumulation and Sclerosis
Supporting outcome
  • Species-resolved profiling shows the murine stromal response reproduces the dominant profibrotic cytokines of human PMP, supporting use of the model for fibrosis studies.
Refuting outcome
  • The murine response diverges on the profibrotic axis specifically, indicating the model is informative for tumour-cell behaviour but not for the sclerosis this node describes.
Would suppressing mucin secretion control this disease better than killing the cells that secrete it?
KNOWLEDGE GAP OPEN gap_secretion_versus_proliferation_target
Attached to
pathophysiology#MUC2 Hypersecretion treatments#Mucolytic Therapy (investigational)
The entry's mechanism says the lethal agent is the secreted product, and the driver genetics agree - GNAS mutation in 83% of cases acts through cAMP on precisely the secretory phenotype. Yet every established treatment targets cells: resect them, or perfuse them with cytotoxic drug. Recurrence after complete cytoreduction with HIPEC remains frequent. Nobody has tested whether pharmacologically suppressing secretion, as opposed to dissolving mucin already deposited, changes the course. The two are different interventions with different windows: mucolysis treats accumulated disease, secretion blockade would prevent accumulation, and only the second could plausibly be given long term after cytoreduction. The experiment is tractable because the pathway is known and druggable at several points, and because low-grade PMP is indolent enough that a secretion-suppressing agent would have time to show an effect.
Proposed experiments
cAMP-pathway secretion blockade versus cytotoxic control in GNAS-mutant PMP models
pmp_secretion_blockade_vs_cytotoxicity
In patient-derived GNAS-mutant PMP models, compare mucin output and disease accumulation under cAMP-pathway blockade against a cytotoxic comparator matched for effect on cell viability, separating suppression of secretion from killing of secreting cells.
Would support
pathophysiology#MUC2 Hypersecretion
Supporting outcome
  • Secretion blockade reduces mucin accumulation at doses that do not reduce viable tumour cell number, establishing secretion as an independently targetable step.
Refuting outcome
  • Mucin accumulation tracks tumour cell number regardless of pathway blockade, which would make secretion a read-out of tumour burden rather than a separate target and redirect effort back to cytoreduction.
When the appendiceal primary and the peritoneal disease are graded differently, which grade predicts outcome?
KNOWLEDGE GAP OPEN gap_grade_discordance
Attached to
diagnosis#Histopathological Grading by PSOGI Classification histopathology#Mucinous Epithelium in Extracellular Mucin Pools
Grade is the only independent predictor of survival, and in 13% of a contemporary series the primary neoplasm and its matching peritoneal disease did not carry the same grade. Those two facts together mean that in one case in eight the prognostic variable depends on which specimen was graded, and the literature does not say which one to use. It is a directly consequential gap: grade drives the decision to offer or withhold a major operation with substantial morbidity.
Proposed experiments
Outcome analysis of grade-discordant appendiceal and peritoneal specimens
pmp_discordant_grade_outcome
In a multi-centre cohort with both primary and peritoneal specimens graded independently, model overall survival against primary grade, peritoneal grade and the higher of the two, and compare their predictive performance in the discordant subset.
Would support
diagnosis#Histopathological Grading by PSOGI Classification
Supporting outcome
  • Peritoneal grade predicts survival better than primary grade in discordant cases, which would make grading of peritoneal material the standard and settle the question.
Refuting outcome
  • Neither specimen predicts better than the higher of the two, which would argue for taking the worst grade found on any material and would simplify the decision rule.
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Pathophysiology

8
KRAS and GNAS Driver Mutations in Appendiceal Mucinous Epithelium
The initiating lesion is a somatic driver pair in the epithelium of an appendiceal mucinous neoplasm. In the largest systematically sequenced series - 167 verified PMP patients analysed by targeted sequencing and droplet digital PCR - KRAS was mutated in 148 cases and GNAS in 139, that is 89% and 83%. Two features make this genotype notable. It is far more consistent than most solid tumours manage, which is what supports treating these as true drivers rather than passengers. And it differs sharply from colorectal adenocarcinoma, where GNAS mutation is uncommon - so the molecular profile distinguishes an appendiceal origin from a colorectal one, which is a question the pathology often has to answer.
KRAS hgnc:6407 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves KRAS (hgnc:6407). hgnc:6407 is a gene from the HUGO Gene Nomenclature Committee. GNAS hgnc:4392 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves GNAS (hgnc:4392). hgnc:4392 is a gene from the HUGO Gene Nomenclature Committee.
Downstream
Constitutive Ras-MAPK and Gs-cAMP Signalling Both drivers are activating: hotspot KRAS codon 12 substitutions and GNAS codon 201 substitutions each lock their pathway on.
Show evidence (2 references)
PMID:41868810 SUPPORT Human Clinical
"The frequency of KRAS and GNAS mutations was analyzed in tumor samples from 167 patients with verified PMP using targeted DNA sequencing and/or droplet digital polymerase chain reaction."
The cohort and the methods behind the frequency figures quoted in this node's description.
PMID:41868810 SUPPORT Human Clinical
"High frequencies of KRAS and GNAS mutations support the proposed role as driver mutations and as potential therapy targets."
The authors' own reading of those frequencies as establishing driver status, which is what this node asserts.
Constitutive Ras-MAPK and Gs-cAMP Signalling
The two drivers act on different pathways and converge on the same cell. Mutant KRAS holds Ras-MAPK signalling on, supporting proliferation and survival of the neoplastic epithelium. Mutant GNAS locks the stimulatory G protein on, raising cAMP. The cAMP arm is the one that matters for what this disease does. Elevated cAMP is a recognised driver of mucin transcription and secretion, so the second driver acts directly on the hypersecretory phenotype rather than simply adding proliferative drive - which is the mechanistic reason a mostly low-grade neoplasm produces a lethal syndrome.
Ras protein signal transduction GO:0007265 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Ras protein signal transduction (GO:0007265). GO:0007265 is a biological process from the Gene Ontology. ↑ INCREASED adenylate cyclase-activating G protein-coupled receptor signaling pathway GO:0007189 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased adenylate cyclase-activating G protein-coupled receptor signaling pathway (GO:0007189). GO:0007189 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
MUC2 Hypersecretion The known intermediate is cAMP-driven upregulation of mucin gene expression. Typed indirect because the transcriptional step between raised cAMP and the measured mucin output has not been mapped in PMP tissue specifically.
Show evidence (1 reference)
PMID:41868810 SUPPORT INDIRECT Human Clinical
"High frequencies of KRAS and GNAS mutations support the proposed role as driver mutations and as potential therapy targets."
INDIRECT because it establishes that these are the drivers without demonstrating the signalling states this node names; the pathway consequences are inferred from the known biochemistry of the hotspot alleles.
MUC2 Hypersecretion
The neoplastic epithelium secretes mucin massively, and MUC2 is the dominant species. MUC2 is extraordinarily glycosylated - glycan accounts for 80% to 90% of its dry weight - and it is that glycan mass, not the protein backbone, that gives the mucus its volume and its viscoelasticity. This node is the entry's pivot. Everything upstream is ordinary neoplasia; everything downstream is a consequence of the secreted product rather than of the cells that secrete it.
mucin-secreting neoplastic epithelial cell CL:0000160 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves mucin-secreting neoplastic epithelial cell, annotated with goblet cell (CL:0000160). CL:0000160 is a cell type from the Cell Ontology.
mucus secretion GO:0070254 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased mucus secretion (GO:0070254). GO:0070254 is a biological process from the Gene Ontology. ↑ INCREASED protein O-linked glycosylation GO:0006493 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves protein O-linked glycosylation (GO:0006493). GO:0006493 is a biological process from the Gene Ontology.
vermiform appendix UBERON:0001154 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in vermiform appendix (UBERON:0001154). UBERON:0001154 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Appendiceal Distension and Perforation Mucin accumulating in an obstructed appendiceal lumen raises intraluminal pressure until the wall gives way.
Progressive Intraperitoneal Mucin Accumulation and Sclerosis Once the epithelium is on the peritoneal surfaces it continues to secrete, so hypersecretion drives the peritoneal phase directly as well as causing the escape that starts it.
Show evidence (3 references)
PMID:34703312 SUPPORT Other
"Mucin 2 (MUC2) is the main type of mucin in PMP and plays a key role in the progressive sclerosis of mucus."
Identifies MUC2 as the dominant mucin and links it to the sclerosis that makes the accumulation dangerous.
PMID:34703312 SUPPORT Other
"The results show that MUC2 is a highly glycosylated protein, with glycan accounts for 80% to 90% of the dry weight."
The glycan fraction, which is why O-glycosylation is bound here and why the glycosylation machinery is a therapeutic target rather than the protein itself.
PMID:41947779 SUPPORT Other
"Represented by mucin2 (MUC2), mucins are the source of mucus viscoelasticity."
Ties MUC2 specifically to the physical property that produces the downstream mechanical disease.
Appendiceal Distension and Perforation
The mechanical event that converts a confined neoplasm into a peritoneal disease. Mucin distends the obstructed appendix until it perforates, releasing both mucin and viable mucin-secreting cells into the peritoneal cavity. Perforation is the single step that determines whether a patient has an appendiceal neoplasm or this disease. It is also the only point at which the disease is straightforwardly preventable, by resecting the neoplasm intact beforehand.
vermiform appendix UBERON:0001154 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in vermiform appendix (UBERON:0001154). UBERON:0001154 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Peritoneal Redistribution and Implantation Perforation delivers the cells to the peritoneal cavity, where fluid dynamics take over.
Show evidence (2 references)
PMID:41868810 SUPPORT Other
"It is commonly caused by ruptured appendiceal mucinous neoplasms seeding tumor cells and mucin into the peritoneal cavity."
Names rupture as the causal event and both of the things it releases.
PMID:34703312 SUPPORT Other
"Pseudomyxoma peritonei (PMP) is a clinical syndrome of malignant tumors, which is caused by a primary mucinous tumor that breaks through the primary organ, following spread and implantation in the peritoneum."
The same sequence stated as the definition of the syndrome: breach of the primary organ, then spread, then implantation.
Peritoneal Redistribution and Implantation
Released cells are not invasive in the ordinary sense. They are carried passively on peritoneal fluid currents and settle where fluid is resorbed or where it pools - the greater omentum, the paracolic gutters, the pelvis, the undersurface of the diaphragm and, in women, the ovaries. Surfaces swept by peristalsis, particularly the small bowel serosa, are relatively spared. That distribution is the clinical signature of the disease and the reason cytoreductive surgery is feasible at all: the deposits sit on surfaces rather than infiltrating through them. Ovarian involvement is common enough to be a diagnostic trap - two thirds of women in a contemporary series - and historically led to these tumours being called primary ovarian.
peritoneum UBERON:0002358 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in peritoneum (UBERON:0002358). UBERON:0002358 is an anatomical location from the Uberon multi-species anatomy ontology. omentum UBERON:0003688 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in omentum (UBERON:0003688). UBERON:0003688 is an anatomical location from the Uberon multi-species anatomy ontology. ovary UBERON:0000992 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in ovary (UBERON:0000992). UBERON:0000992 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Progressive Intraperitoneal Mucin Accumulation and Sclerosis Implanted epithelium continues to secrete at its new sites.
Show evidence (1 reference)
PMID:39327362 SUPPORT Human Clinical
"Ovarian involvement was observed in 43/65 females (66.2%)."
Quantifies ovarian involvement in a consecutive series, supporting both the distribution claim and the diagnostic trap described here.
Progressive Intraperitoneal Mucin Accumulation and Sclerosis
Mucin accumulates faster than the peritoneum can clear it, and it does not stay fluid. Progressive sclerosis converts soft mucus into a stiff, adherent mass that encases viscera and fixes them to one another and to the abdominal wall. The primary literature is explicit that this - not metastasis, not cachexia from tumour burden - is the key pathological mechanism and the main cause of death. It is the justification for treating mucin itself as a therapeutic target.
peritoneum UBERON:0002358 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in peritoneum (UBERON:0002358). UBERON:0002358 is an anatomical location from the Uberon multi-species anatomy ontology.
Animal models
PMP patient-derived xenograft (PDX) mouse Mouse partially recapitulates Reproduces the peritoneal mucinous tumour and its inflammatory microenvironment, which is the compartment where this node's fibrosis and sclerosis develop.
Downstream
Mechanical Visceral Compromise A stiff, expanding intraperitoneal mass compresses and tethers hollow viscera.
Show evidence (2 references)
PMID:34703312 SUPPORT Other
"The mucus sclerosis is the key pathological mechanism in the development of PMP, and the main cause of death."
The central claim of this entry, stated by the source in exactly those terms.
PMID:34703312 SUPPORT Other
"Excessive mucus secretion is also the main cause of death."
Restates the same conclusion about the secreted product rather than the tumour cells.
Mechanical Visceral Compromise
The clinical endpoint. Progressive abdominal distension, intractable pain, intestinal obstruction, organ adhesion and eventually cachexia, as the encased bowel can neither move nor absorb.
peritoneum UBERON:0002358 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in peritoneum (UBERON:0002358). UBERON:0002358 is an anatomical location from the Uberon multi-species anatomy ontology.
Show evidence (1 reference)
PMID:34703312 SUPPORT Other
"Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei (PMP), which often leads to significant increase in abdominal circumference, intractable abdominal pain, progressive intestinal obstruction, abdominal organ adhesions, and cachexia."
Enumerates the mechanical consequences this node collects, and attributes them to the secreted mucus.
Intratumoral Hypoxia
Mucinous nodules that grow beyond their diffusion limit become hypoxic, and hypoxia is not a passive endpoint here: HIF-1alpha binds the MUC2 promoter directly and raises MUC2 transcription. That closes a loop. Secreted mucin drives the tissue expansion that creates the hypoxia, and the hypoxia drives more mucin. It is the one place in this entry where the chain stops being a chain, and it matters practically as well as descriptively - it makes HIF-1alpha a target whose inhibition reduces mucinous tumour growth in a xenograft model, which is a therapeutic entry point aimed at the secreted product rather than at proliferation.
response to hypoxia GO:0001666 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased response to hypoxia (GO:0001666). GO:0001666 is a biological process from the Gene Ontology. ↑ INCREASED
Animal models
Intraperitoneal murine xenograft of PMP (HIF-1α inhibition) Mouse rescues Pharmacological HIF-1α inhibition in this model reduced both MUC2 expression and mucinous tumour growth, testing the amplification loop by interrupting it.
Downstream
MUC2 Hypersecretion HIF-1alpha binding at the MUC2 promoter increases MUC2 transcription, feeding back on the node whose product created the hypoxic tissue in the first place.
Show evidence (2 references)
PMID:26589109 SUPPORT In Vitro
"In vitro exposure of LS174T cells to hypoxia increased MUC2 messenger RNA (mRNA) and protein expression and increased HIF-1α binding to the MUC2 promoter."
The direct promoter-binding result that makes this an amplification edge rather than a correlation.
PMID:26589109 SUPPORT Model Organism
"In a murine xenograft model of PMP, chronic oral therapy with BAY 87-2243 inhibited mucinous tumor growth and MUC2, HIF-1α expression in the tumor tissue."
Interrupting the loop pharmacologically reduces both MUC2 and tumour growth, which is the functional test of the edge.
✶

Histopathology

1
Mucinous Epithelium in Extracellular Mucin Pools
Histological grade is what the classification turns on, and in a 155-case series it was the only independent prognostic factor for overall survival on multivariate analysis - outperforming lymph node metastasis, angiolymphatic invasion, Ki67 index and p53 status, all of which looked prognostic on univariate testing. The grades run from acellular mucin, through low-grade mucinous carcinoma peritonei, to high-grade, to high-grade with signet ring cells. Roughly two thirds of cases are low-grade.
Show evidence (2 references)
PMID:31926211 SUPPORT Human Clinical
"But Multivariate analysis identified only histologic grade was the independent prognostic factor for OS."
The multivariate result that makes grade the dominant pathological variable.
PMID:31926211 SUPPORT Human Clinical
"The patients included 63.2% (n = 98) low-grade mucinous carcinoma peritonei, 31.6% (n = 49) high-grade mucinous carcinoma peritonei and 5.2% (n = 8) high-grade mucinous carcinoma peritonei with signet ring cells."
The grade distribution behind the proportions quoted in this entry.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Pseudomyxoma Peritonei Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

4
Digestive 2
Progressive Abdominal Distension VERY_FREQUENT Abdominal distention HP:0003270 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal distention (HP:0003270), qualified as course progressive. HP:0003270 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:34703312 SUPPORT Other
"Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei (PMP), which often leads to significant increase in abdominal circumference, intractable abdominal pain, progressive intestinal obstruction, abdominal organ adhesions, and cachexia."
Names increased abdominal circumference as the most prominent feature; the source for this and the two phenotypes below.
Progressive Intestinal Obstruction FREQUENT HP:0005214 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intestinal obstruction (HP:0005214), qualified as course progressive. HP:0005214 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:34703312 SUPPORT Other
"Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei (PMP), which often leads to significant increase in abdominal circumference, intractable abdominal pain, progressive intestinal obstruction, abdominal organ adhesions, and cachexia."
Names progressive intestinal obstruction and attributes it to mucus accumulation.
Constitutional 1
Intractable Abdominal Pain FREQUENT HP:0002027 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal pain (HP:0002027), qualified as temporality chronic. HP:0002027 is a phenotype from the Human Phenotype Ontology.
Temporal: CHRONIC
Show evidence (1 reference)
PMID:34703312 SUPPORT Other
"Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei (PMP), which often leads to significant increase in abdominal circumference, intractable abdominal pain, progressive intestinal obstruction, abdominal organ adhesions, and cachexia."
Names intractable abdominal pain among the consequences of mucus accumulation.
Other 1
Ovarian Involvement FREQUENT Ovarian neoplasm HP:0100615 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ovarian neoplasm (HP:0100615). HP:0100615 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39327362 SUPPORT Human Clinical
"Ovarian involvement was observed in 43/65 females (66.2%)."
The frequency in a consecutive surgical series, which is what supports the FREQUENT band.
🧬

Genetic Associations

5
KRAS (Activating somatic KRAS mutations, predominantly at codon 12, are present in the large majority of PMP - 148 of 167 cases (89%) in the largest systematically sequenced series. They are somatic drivers in the appendiceal epithelium, not germline predisposition alleles. Unlike in colorectal cancer, KRAS status has not consistently predicted survival in PMP series, so its role here is causal rather than prognostic.)
Gene: KRAS hgnc:6407 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is KRAS (hgnc:6407). hgnc:6407 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (1 reference)
PMID:41868810 SUPPORT Human Clinical
"High frequencies of KRAS and GNAS mutations support the proposed role as driver mutations and as potential therapy targets."
The driver claim for both genes, from the series that measured their frequency.
GNAS (Activating somatic GNAS mutations at codon 201 are present in 139 of 167 cases (83%) in the same series, and co-occur with KRAS far more often than chance. GNAS is the mechanistically interesting driver: locking Gs on raises cAMP, and cAMP drives mucin secretion. A high GNAS mutation rate in a disease whose lethal agent is secreted mucin is not a coincidence, and it is the strongest argument that the hypersecretory phenotype is genetically driven rather than incidental. Its high frequency in PMP against a low frequency in colorectal adenocarcinoma also makes it useful for assigning appendiceal origin.)
Gene: GNAS hgnc:4392 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is GNAS (hgnc:4392). hgnc:4392 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (1 reference)
PMID:41868810 SUPPORT Human Clinical
"The frequency of KRAS and GNAS mutations was analyzed in tumor samples from 167 patients with verified PMP using targeted DNA sequencing and/or droplet digital polymerase chain reaction."
The cohort and assay behind the GNAS frequency quoted here.
TP53 (TP53 mutation is the grade-associated alteration rather than a universal driver. In a 114-patient cohort stratified by predominant genomic alteration, half of TP53-mutant tumours were WHO grade 3, against 38% of triple-negative, 10% of RAS-mutant and 7% of GNAS-mutant tumours - so TP53 marks the aggressive end of a disease whose baseline genotype is KRAS and GNAS.)
Gene: TP53 hgnc:11998 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TP53 (hgnc:11998). hgnc:11998 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (1 reference)
PMID:39812318 SUPPORT Human Clinical
"Fifty percent of TP53 -mut were WHO grade 3 compared with 38% triple-negative, 10% RAS -mut, and 7% GNAS -mut tumors"
The grade distribution across molecular groups. Quoted with the source's own irregular spacing around the gene names, which is a typesetting artefact of the cached record rather than the authors' usage.
BRAF (A minority somatic driver - 3 of 35 tumours in the sequenced series - but the one with a directly actionable consequence. BRAF-mutant disease is the subgroup for which a licensed targeted agent class already exists, which is why it is curated separately from the commoner KRAS and GNAS events rather than folded into an "other mutations" line. This is the concrete content behind the entry's diagnosis section, which otherwise refers to targetable drivers without naming one.)
Gene: BRAF hgnc:1097 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is BRAF (hgnc:1097). hgnc:1097 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (2 references)
PMID:41868810 SUPPORT Human Clinical
"The most commonly mutated genes other than KRAS/GNAS were SMAD4 (9/35), PIC3CA (7/35), TP53 (6/35), FBXW7 (4/35), and BRAF (3/35)"
Gives the BRAF mutation frequency in the sequenced cohort. Note the source's own spelling of PIC3CA, which is a typographical error for PIK3CA in the cited text and is quoted here unaltered.
PMID:41868810 SUPPORT Human Clinical
"BRAF mutations, which could be targeted by BRAF inhibitors"
The actionability claim that makes this gene worth separating out.
SMAD4 (The most frequent somatic mutation after KRAS and GNAS (9 of 35), and reported as associated with inferior outcome. Curated as prognostic rather than mechanistic: this entry does not model a SMAD4-specific pathway, and the association is drawn from a single series.)
Gene: SMAD4 hgnc:6770 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SMAD4 (hgnc:6770). hgnc:6770 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (1 reference)
PMID:41868810 SUPPORT Human Clinical
"the most interesting findings were mutations in SMAD4, which were associated with inferior outcome"
The prognostic association, stated by the sequencing series itself.
💊

Medical Actions

5
Cytoreductive Surgery
Action: cytoreductive surgeryNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is cytoreductive surgery (NCIT:C132068). NCIT:C132068 is a clinical intervention from the NCI Thesaurus. Ontology label: Cytoreductive Surgery NCIT:C132068
Surgical removal of all visible tumour and mucin, typically with peritonectomy and resection of involved viscera. It is the definitive treatment, and it works because the disease sits on peritoneal surfaces rather than infiltrating through them. Completeness of cytoreduction is the operative variable that matters, which is why the procedure is centralised to high-volume units.
Mechanism Target:
Progressive Intraperitoneal Mucin Accumulation and Sclerosis — Removes the accumulated mucin and the implanted epithelium producing it, addressing both the product and its source.
Show evidence (1 reference)
PMID:34703312 SUPPORT Other
"Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is the recommended treatment for PMP."
Establishes the combined procedure as recommended treatment; the source for this and the HIPEC entry below.
Hyperthermic Intraperitoneal Chemotherapy
Action: hyperthermic intraperitoneal chemotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is hyperthermic intraperitoneal chemotherapy (NCIT:C91835). NCIT:C91835 is a clinical intervention from the NCI Thesaurus. Ontology label: Hyperthermic Intraperitoneal Chemotherapy NCIT:C91835
Agent: mitomycin C CHEBI:27504 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses mitomycin C (CHEBI:27504). CHEBI:27504 is a therapeutic agent from Chemical Entities of Biological Interest. oxaliplatin CHEBI:31941 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses oxaliplatin (CHEBI:31941). CHEBI:31941 is a therapeutic agent from Chemical Entities of Biological Interest.
Heated chemotherapy perfused through the peritoneal cavity immediately after cytoreduction, to treat residual microscopic disease on surfaces that surgery cannot clear. Given regionally rather than systemically because the disease is confined to the peritoneal compartment. Recurrence remains frequent even after complete cytoreduction with HIPEC, which is what motivates the mucolytic approach below.
Mechanism Target:
Peritoneal Redistribution and Implantation — Targets residual implanted epithelium left on peritoneal surfaces after cytoreduction.
Show evidence (2 references)
PMID:34703312 SUPPORT Other
"Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is the recommended treatment for PMP."
Names HIPEC as part of the recommended combined treatment.
PMID:34703312 SUPPORT Other
"However, recurrence is frequently observed even after CRS and HIPEC, presenting similar clinical manifestations."
PARTIAL because it qualifies the treatment rather than supporting it: recurrence is frequent despite the recommended regimen.
Mucolytic Therapy (investigational)
Dissolving mucin directly, rather than resecting it or killing the cells that make it. The rationale follows from this entry's central claim: if the secreted product is what kills, then degrading it is a rational target in its own right. Approaches under investigation act on mucin O-glycosylation - the glycan that carries most of the molecule's mass and all of its viscoelasticity - including inhibitors of the glycosyltransferases that build it and nucleotide-sugar analogues that starve them of substrate. Investigational. No clinical outcome data exist; the literature to date is review and preclinical.
Mechanism Target:
Progressive Intraperitoneal Mucin Accumulation and Sclerosis — Acts on the accumulated mucin itself, which is the node this entry identifies as the cause of death.
Show evidence (2 references)
PMID:41947779 SUPPORT Other
"Effective mucolytic therapy can greatly improve the efficacy of cytoreductive surgery + hyperthermic intraperitoneal chemotherapy, alleviate symptoms and improve prognosis for pseudomyxoma peritonei (PMP) patients."
PARTIAL because the source states the expected benefit of effective mucolysis as a premise for review rather than reporting an achieved clinical result.
PMID:41947779 SUPPORT Other
"The main components of PMP mucus are highly O-glycosylated proteins called mucins."
Establishes O-glycosylation as the property these approaches target.
Systemic Chemotherapy
Action: chemotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is chemotherapy (NCIT:C15632). NCIT:C15632 is a clinical intervention from the NCI Thesaurus. Ontology label: Chemotherapy NCIT:C15632
Agent: oxaliplatin CHEBI:31941 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses oxaliplatin (CHEBI:31941). CHEBI:31941 is a therapeutic agent from Chemical Entities of Biological Interest. fluorouracil CHEBI:46345 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses fluorouracil, annotated with 5-fluorouracil (CHEBI:46345). CHEBI:46345 is a therapeutic agent from Chemical Entities of Biological Interest.
Oxaliplatin/5-fluorouracil/leucovorin-type regimens given systemically, for disease that cannot be completely cytoreduced or that has recurred beyond further surgery. This is second-line by necessity rather than by preference. The compartment argument that makes intraperitoneal delivery attractive works against systemic delivery: a poorly vascularised mucin lake is a difficult target for a drug arriving through the blood, and response rates in this histology are correspondingly modest. It is curated here because it is what patients with unresectable disease actually receive.
Mechanism Target:
Peritoneal Redistribution and Implantation — Directed at implanted epithelium that cytoreduction cannot reach or has left behind.
Show evidence (1 reference)
clinicaltrials:NCT00352755 SUPPORT Human Clinical
"Patients with peritoneal carcinomatosis or pseudomyxoma peritonei will undergo debulking surgery with peritonectomy and placement of adhesive barrier film followed by repeated delayed intraperitoneal chemotherapy with 5FU with systemic oxaliplatin-based chemotherapy on a biweekly schedule."
A Phase II protocol administering systemic oxaliplatin/5FU/leucovorin in this disease, establishing the regimen as one given to these patients.
Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC)
Action: chemotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is chemotherapy (NCIT:C15632). NCIT:C15632 is a clinical intervention from the NCI Thesaurus. Ontology label: Chemotherapy NCIT:C15632
Agent: cisplatin CHEBI:27899 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses cisplatin (CHEBI:27899). CHEBI:27899 is a therapeutic agent from Chemical Entities of Biological Interest. doxorubicin CHEBI:28748 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses doxorubicin (CHEBI:28748). CHEBI:28748 is a therapeutic agent from Chemical Entities of Biological Interest.
Low-dose chemotherapy delivered into the abdomen as a pressurized aerosol at laparoscopy, for unresectable or recurrent disease. The rationale is distribution rather than dose: an aerosol reaches peritoneal surfaces that a liquid instillation pools away from, which is the same compartment logic behind HIPEC applied to patients who cannot have surgery. Evidence in this disease specifically is thin - a single case report - and it is curated at that strength rather than as an established option.
Mechanism Target:
Progressive Intraperitoneal Mucin Accumulation and Sclerosis — Aimed at the accumulating peritoneal disease in patients who are not cytoreduction candidates.
Show evidence (1 reference)
PMID:26076000 SUPPORT Human Clinical
"PIPAC achieved clinical and histological disease remission."
The reported outcome. A single case, which is why this treatment is described as investigational rather than standard.
🔬

Biochemical Markers

4
Serum Carcinoembryonic Antigen (CEA)
Show evidence (2 references)
PMID:27038681 SUPPORT Human Clinical
"We found preoperative CEA serum values to correlate with peritoneal cancer index."
Ties the serum measurement to the disease-burden index used for surgical planning.
PMID:27038681 SUPPORT Human Clinical
"Thus, serum CEA measurements did not reflect aggressiveness of these tumors."
PARTIAL because it qualifies the marker rather than supporting it. In the aggressive signet-ring cases with nonpolarized CEA staining, serum values were normal and the patients died within five years - so a normal CEA does not exclude the worst-prognosis subgroup.
Serum CA19-9
Show evidence (1 reference)
PMID:27038681 SUPPORT Human Clinical
"CA19-9 showed strong immunopositivity in most of the tumors (91.3%), and mutated enzyme FUT3 was demonstrated from the cases showing negative or weak staining."
Gives both the expression frequency and the mechanistic reason some tumours are marker-negative.
Serum CA125
Show evidence (1 reference)
PMID:27038681 SUPPORT Human Clinical
"CA125 was infrequently expressed by tumor cells (focal staining in 6.5% of the cases), but in most of the cases (79.3%), adjacent nonneoplastic mesothelial cells showed immunopositivity."
Establishes the mesothelial rather than tumour-cell origin of the CA125 signal.
Combined Serum Marker Panel
Show evidence (1 reference)
PMID:34733775 SUPPORT Human Clinical
"CEA, CA125, CA19-9, CA724, and CA242 in serum and ascites can be used to judge the severity and predict the resectability."
The panel's stated clinical role, from a study designed to evaluate exactly that.
🔬

Diagnosis

2
Histopathological Grading by PSOGI Classification
Grading is the diagnostic act that matters, because it is the only independent predictor of survival. The scheme separates acellular mucin, low-grade PMP, high-grade PMP and PMP with signet ring cells, and the survival separation between those groups is wide. Grade of the peritoneal disease is not always the grade of the primary: in 13% of a contemporary series the appendiceal neoplasm and its matching PMP were graded differently, so the peritoneal disease has to be graded on its own material.
Show evidence (2 references)
PMID:39327362 SUPPORT Human Clinical
"Median OS was 13.8 years, and 5-year OS rates were 100%, 74.4%, 44.4%, and 20% for acellular mucin, low-grade PMP, high-grade PMP and PMP-SRC, respectively"
The survival separation between grades, which is what makes grading the decisive diagnostic step.
PMID:31926211 SUPPORT Human Clinical
"But Multivariate analysis identified only histologic grade was the independent prognostic factor for OS."
Establishes grade as the only variable surviving multivariate adjustment.
KRAS and GNAS Mutation Testing
Molecular testing serves two purposes. It supports appendiceal origin, since the KRAS-plus-GNAS pattern is uncommon in colorectal adenocarcinoma. And it identifies targetable drivers as agents against them become available. There is a practical trap: peritoneal tumour samples have low cellularity, which is the main reason reported mutation frequencies have varied so widely. Testing the primary appendiceal tumour instead raises the detection rate.
Show evidence (1 reference)
PMID:41868810 SUPPORT Human Clinical
"The frequency of KRAS and GNAS mutations was analyzed in tumor samples from 167 patients with verified PMP using targeted DNA sequencing and/or droplet digital polymerase chain reaction."
The assay approach, including the sensitive digital PCR method used because of low tumour cellularity.
📈

Progression

3
Occult appendiceal phase
A mucinous neoplasm distends the appendix without peritoneal disease. Often silent, and sometimes found incidentally at appendicectomy - the one window in which the disease can be prevented rather than treated.
Show evidence (1 reference)
PMID:41868810 SUPPORT Other
"It is commonly caused by ruptured appendiceal mucinous neoplasms seeding tumor cells and mucin into the peritoneal cavity."
Establishes the appendiceal neoplasm as the antecedent lesion that must rupture for the peritoneal phase to begin.
Peritoneal accumulation phase
After perforation, mucin accumulates over years. Indolent in low-grade disease, which is why patients often present late with gross distension rather than early with pain.
Show evidence (1 reference)
PMID:41868810 SUPPORT Other
"Pseudomyxoma peritonei (PMP) is a rare, progressive, but generally slow-growing abdominal cancer with an incidence rate of 3.2 people per million per year"
Characterises the tempo of this phase as progressive but slow-growing.
Mechanical decompensation
Sclerosed mucin encases the viscera, producing obstruction, adhesion and cachexia. Survival at this stage is grade-dependent: five-year overall survival runs from 100% for acellular mucin down to 20% for disease with signet ring cells.
Show evidence (1 reference)
PMID:39327362 SUPPORT Human Clinical
"Median OS was 13.8 years, and 5-year OS rates were 100%, 74.4%, 44.4%, and 20% for acellular mucin, low-grade PMP, high-grade PMP and PMP-SRC, respectively"
The grade-stratified survival figures quoted here.
📊

Prevalence

1
Worldwide
Annual Incidence 0.32 per 100,000 <1 in 1,000,000
3.2 per million per year, converted to 0.32 per 100,000. Figure quoted by a 2026 sequencing series citing the underlying epidemiological source.
Show evidence (1 reference)
PMID:41868810 SUPPORT Other
"Pseudomyxoma peritonei (PMP) is a rare, progressive, but generally slow-growing abdominal cancer with an incidence rate of 3.2 people per million per year"
The incidence figure this record normalises. Typed OTHER because the sentence is the paper's background citation of an epidemiological source rather than its own result.
🔬

Clinical Trials

2
NCT01946854 NOT_APPLICABLE ACTIVE_NOT_RECRUITING
Randomized crossover trial of systemic chemotherapy in metastatic well-differentiated mucinous appendiceal adenocarcinoma with pseudomyxoma peritonei. Its premise is the open question this entry's treatment section reflects - whether systemic chemotherapy affects this histology at all.
Show evidence (1 reference)
clinicaltrials:NCT01946854 SUPPORT Human Clinical
"Appendiceal cancer is a rare disease that does not cause many symptoms. As such, doctors are not sure if chemotherapy actually has an effect on the disease."
The registration record states the uncertainty the trial was designed to resolve.
NCT00352755 PHASE_II TERMINATED
Phase II study of debulking with peritonectomy plus biweekly intraperitoneal 5-FU and systemic oxaliplatin/5-FU/leucovorin. Terminated.
Show evidence (1 reference)
clinicaltrials:NCT00352755 SUPPORT Human Clinical
"This formal Phase II study is planned to determine the safety, toxicities and survival of patients with peritoneal carcinomatosis and pseudomyxoma peritonei treated with this regimen."
States the trial's phase, population and endpoints.
🐁

Animal Models

2
PMP patient-derived xenograft (PDX) mouse
Serial engraftment of patient PMP tumour into immunocompromised mice. Both low-grade and high-grade donors were engrafted, and the resulting tumours were histopathologically similar to human PMP. The model's declared purpose is the tumour-stroma interface rather than the tumour cells alone, and its design makes that tractable in an unusual way: the tumour is human and the stroma is murine, so the species of a given cytokine identifies its cellular source.
Species
Mouse
Publication
PMID:26833741
Pathograph links
Progressive Intraperitoneal Mucin Accumulation and Sclerosis partially recapitulates fidelity: moderate Reproduces the peritoneal mucinous tumour and its inflammatory microenvironment, which is the compartment where this node's fibrosis and sclerosis develop.
Limitations: The inflammatory environment is reproduced but not faithfully: IL-6 and IL-8/KC/MIP2 differed significantly between human and PDX ascites, and the cytokines were secreted mostly by murine stromal cells rather than by the human tumour cells. Any inference about human tumour-cell signalling drawn from this model is therefore indirect.
Readouts
Ascites cytokine profile
Direction: ALTERED
Interpretation: Cytokines elevated in human PMP were also elevated in PDX ascites, establishing the model's inflammatory phenotype while the species differences bound its fidelity.
Show evidence (1 reference)
PMID:26833741 SUPPORT Model Organism
"Cytokines previously shown to be elevated in human PMP were also elevated in PDX ascites."
The measurement establishing that the model reproduces the inflammatory milieu.
Show evidence (1 reference)
PMID:26833741 SUPPORT Model Organism
"PDX mouse models of low- and high-grade PMP were generated and were of a similar histopathology as human PMP."
Establishes that the model reproduces the disease's histopathology across both grade tiers, which is what makes it informative for this node.
Intraperitoneal murine xenograft of PMP (HIF-1α inhibition)
An intraperitoneal xenograft used to test whether interrupting the hypoxia-MUC2 loop reduces mucinous tumour growth. Curated because it is the experimental support for the amplification edge in the pathophysiology section.
Species
Mouse
Publication
PMID:26589109
Pathograph links
Intratumoral Hypoxia rescues fidelity: moderate Pharmacological HIF-1α inhibition in this model reduced both MUC2 expression and mucinous tumour growth, testing the amplification loop by interrupting it.
Limitations: A xenograft in immunocompromised mice, so the immune contribution to the peritoneal environment is absent; and the readout is tumour growth rather than the mechanical visceral compromise that determines outcome in patients.
Readouts
Mucinous tumour growth under HIF-1α inhibition
Direction: DECREASED
Interpretation: Growth and MUC2/HIF-1α expression both fell under chronic oral BAY 87-2243.
Show evidence (1 reference)
PMID:26589109 SUPPORT Model Organism
"In a murine xenograft model of PMP, chronic oral therapy with BAY 87-2243 inhibited mucinous tumor growth and MUC2, HIF-1α expression in the tumor tissue."
The in vivo result behind the therapeutic rationale for targeting this loop.
{ }

Source YAML

click to show 
name: Pseudomyxoma Peritonei
creation_date: "2026-08-26T16:00:00Z"
category: Neoplastic
disease_term:
  preferred_term: pseudomyxoma peritonei
  term:
    id: MONDO:0017048
    label: pseudomyxoma peritonei
synonyms:
- PMP
- jelly belly
- disseminated peritoneal adenomucinosis
- peritoneal mucinous carcinomatosis
description: >-
  A rare peritoneal syndrome in which a mucinous neoplasm - almost always of the appendix -
  perforates and redistributes mucin-secreting epithelium across the peritoneal surfaces,
  which then accumulate mucin progressively until abdominal organs are mechanically
  compromised. Incidence is around 3.2 per million per year.

  Three things distinguish it from the way solid tumours usually behave, and the entry is
  built around them.

  The lethal agent is a secreted product, not the cells. Patients are killed by mucin.
  Tumour cell burden can be modest while litres of mucus accumulate, stiffen, and encase
  the viscera; the mucus sclerosis is described in the primary literature as the key
  pathological mechanism and the main cause of death. Curating this as a disease of
  hypersecretion rather than of proliferation is the entry's organising decision.

  Its driver genetics are unusually clean and unusually consistent. KRAS and GNAS are
  mutated in the large majority of cases - 89% and 83% respectively in the largest
  systematically sequenced series - and the pair co-occurs far more often than chance. The
  GNAS arm is mechanistically pointed: constitutive Gs-cAMP signalling is a recognised
  driver of mucin hypersecretion, so the second driver acts on precisely the process that
  makes the disease lethal.

  It spreads by fluid mechanics rather than by invasion. Cells are carried on peritoneal
  fluid currents and settle where the fluid is resorbed or pools, which is why omentum,
  paracolic gutters and ovaries are involved while the bowel serosa is often spared. That
  is also why the treatment is a surgical and regional-chemotherapy problem rather than a
  systemic one.

parents:
- Appendiceal Mucinous Neoplasm
- Peritoneal Surface Malignancy

prevalence:
- population: Worldwide
  measure_type: ANNUAL_INCIDENCE
  prevalence_class: BELOW_1_IN_1000000
  rate_per_100000: 0.32
  notes: >-
    3.2 per million per year, converted to 0.32 per 100,000. Figure quoted by a 2026
    sequencing series citing the underlying epidemiological source.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Pseudomyxoma peritonei (PMP) is a rare, progressive, but generally slow-growing
      abdominal cancer with an incidence rate of 3.2 people per million per year
    explanation: >-
      The incidence figure this record normalises. Typed OTHER because the sentence is the
      paper's background citation of an epidemiological source rather than its own result.

pathophysiology:

- name: KRAS and GNAS Driver Mutations in Appendiceal Mucinous Epithelium
  role: trigger
  biological_scale: MOLECULAR
  description: >-
    The initiating lesion is a somatic driver pair in the epithelium of an appendiceal
    mucinous neoplasm. In the largest systematically sequenced series - 167 verified PMP
    patients analysed by targeted sequencing and droplet digital PCR - KRAS was mutated in
    148 cases and GNAS in 139, that is 89% and 83%.

    Two features make this genotype notable. It is far more consistent than most solid
    tumours manage, which is what supports treating these as true drivers rather than
    passengers. And it differs sharply from colorectal adenocarcinoma, where GNAS mutation
    is uncommon - so the molecular profile distinguishes an appendiceal origin from a
    colorectal one, which is a question the pathology often has to answer.
  genes:
  - preferred_term: KRAS
    term:
      id: hgnc:6407
      label: KRAS
  - preferred_term: GNAS
    term:
      id: hgnc:4392
      label: GNAS
  downstream:
  - target: Constitutive Ras-MAPK and Gs-cAMP Signalling
    causal_link_type: DIRECT
    description: >-
      Both drivers are activating: hotspot KRAS codon 12 substitutions and GNAS codon 201
      substitutions each lock their pathway on.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The frequency of KRAS and GNAS mutations was analyzed in tumor samples from 167
      patients with verified PMP using targeted DNA sequencing and/or droplet digital
      polymerase chain reaction.
    explanation: >-
      The cohort and the methods behind the frequency figures quoted in this node's
      description.
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      High frequencies of KRAS and GNAS mutations support the proposed role as driver
      mutations and as potential therapy targets.
    explanation: >-
      The authors' own reading of those frequencies as establishing driver status, which is
      what this node asserts.

- name: Constitutive Ras-MAPK and Gs-cAMP Signalling
  role: mechanism
  biological_scale: MOLECULAR
  description: >-
    The two drivers act on different pathways and converge on the same cell. Mutant KRAS
    holds Ras-MAPK signalling on, supporting proliferation and survival of the neoplastic
    epithelium. Mutant GNAS locks the stimulatory G protein on, raising cAMP.

    The cAMP arm is the one that matters for what this disease does. Elevated cAMP is a
    recognised driver of mucin transcription and secretion, so the second driver acts
    directly on the hypersecretory phenotype rather than simply adding proliferative drive -
    which is the mechanistic reason a mostly low-grade neoplasm produces a lethal syndrome.
  biological_processes:
  - preferred_term: Ras protein signal transduction
    term:
      id: GO:0007265
      label: Ras protein signal transduction
    modifier: INCREASED
  - preferred_term: adenylate cyclase-activating G protein-coupled receptor signaling pathway
    term:
      id: GO:0007189
      label: adenylate cyclase-activating G protein-coupled receptor signaling pathway
    modifier: INCREASED
  downstream:
  - target: MUC2 Hypersecretion
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      The known intermediate is cAMP-driven upregulation of mucin gene expression. Typed
      indirect because the transcriptional step between raised cAMP and the measured mucin
      output has not been mapped in PMP tissue specifically.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      High frequencies of KRAS and GNAS mutations support the proposed role as driver
      mutations and as potential therapy targets.
    explanation: >-
      INDIRECT because it establishes that these are the drivers without demonstrating the
      signalling states this node names; the pathway consequences are inferred from the
      known biochemistry of the hotspot alleles.

- name: MUC2 Hypersecretion
  role: central_effector
  biological_scale: CELLULAR
  description: >-
    The neoplastic epithelium secretes mucin massively, and MUC2 is the dominant species.
    MUC2 is extraordinarily glycosylated - glycan accounts for 80% to 90% of its dry weight -
    and it is that glycan mass, not the protein backbone, that gives the mucus its volume
    and its viscoelasticity.

    This node is the entry's pivot. Everything upstream is ordinary neoplasia; everything
    downstream is a consequence of the secreted product rather than of the cells that
    secrete it.
  cell_types:
  - preferred_term: mucin-secreting neoplastic epithelial cell
    term:
      id: CL:0000160
      label: goblet cell
  biological_processes:
  - preferred_term: mucus secretion
    term:
      id: GO:0070254
      label: mucus secretion
    modifier: INCREASED
  - preferred_term: protein O-linked glycosylation
    term:
      id: GO:0006493
      label: protein O-linked glycosylation
  locations:
  - preferred_term: vermiform appendix
    term:
      id: UBERON:0001154
      label: vermiform appendix
  downstream:
  - target: Appendiceal Distension and Perforation
    causal_link_type: DIRECT
    description: >-
      Mucin accumulating in an obstructed appendiceal lumen raises intraluminal pressure
      until the wall gives way.
  - target: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
    causal_link_type: DIRECT
    description: >-
      Once the epithelium is on the peritoneal surfaces it continues to secrete, so
      hypersecretion drives the peritoneal phase directly as well as causing the escape
      that starts it.
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Mucin 2 (MUC2) is the main type of mucin in PMP and plays a key role in the
      progressive sclerosis of mucus.
    explanation: >-
      Identifies MUC2 as the dominant mucin and links it to the sclerosis that makes the
      accumulation dangerous.
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The results show that MUC2 is a highly glycosylated protein, with glycan accounts for
      80% to 90% of the dry weight.
    explanation: >-
      The glycan fraction, which is why O-glycosylation is bound here and why the
      glycosylation machinery is a therapeutic target rather than the protein itself.
  - reference: PMID:41947779
    reference_title: "Mucin O-Glycosylation and Mucolytic Therapies in Pseudomyxoma Peritonei: Literature Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Represented by mucin2 (MUC2), mucins are the source of mucus viscoelasticity.
    explanation: >-
      Ties MUC2 specifically to the physical property that produces the downstream
      mechanical disease.

- name: Appendiceal Distension and Perforation
  role: mechanism
  biological_scale: TISSUE
  description: >-
    The mechanical event that converts a confined neoplasm into a peritoneal disease. Mucin
    distends the obstructed appendix until it perforates, releasing both mucin and viable
    mucin-secreting cells into the peritoneal cavity.

    Perforation is the single step that determines whether a patient has an appendiceal
    neoplasm or this disease. It is also the only point at which the disease is
    straightforwardly preventable, by resecting the neoplasm intact beforehand.
  locations:
  - preferred_term: vermiform appendix
    term:
      id: UBERON:0001154
      label: vermiform appendix
  downstream:
  - target: Peritoneal Redistribution and Implantation
    causal_link_type: DIRECT
    description: >-
      Perforation delivers the cells to the peritoneal cavity, where fluid dynamics take
      over.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      It is commonly caused by ruptured appendiceal mucinous neoplasms seeding tumor cells
      and mucin into the peritoneal cavity.
    explanation: >-
      Names rupture as the causal event and both of the things it releases.
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Pseudomyxoma peritonei (PMP) is a clinical syndrome of malignant tumors, which is
      caused by a primary mucinous tumor that breaks through the primary organ, following
      spread and implantation in the peritoneum.
    explanation: >-
      The same sequence stated as the definition of the syndrome: breach of the primary
      organ, then spread, then implantation.

- name: Peritoneal Redistribution and Implantation
  role: mechanism
  biological_scale: TISSUE
  description: >-
    Released cells are not invasive in the ordinary sense. They are carried passively on
    peritoneal fluid currents and settle where fluid is resorbed or where it pools - the
    greater omentum, the paracolic gutters, the pelvis, the undersurface of the diaphragm
    and, in women, the ovaries. Surfaces swept by peristalsis, particularly the small bowel
    serosa, are relatively spared.

    That distribution is the clinical signature of the disease and the reason cytoreductive
    surgery is feasible at all: the deposits sit on surfaces rather than infiltrating
    through them.

    Ovarian involvement is common enough to be a diagnostic trap - two thirds of women in a
    contemporary series - and historically led to these tumours being called primary
    ovarian.
  locations:
  - preferred_term: peritoneum
    term:
      id: UBERON:0002358
      label: peritoneum
  - preferred_term: omentum
    term:
      id: UBERON:0003688
      label: omentum
  - preferred_term: ovary
    term:
      id: UBERON:0000992
      label: ovary
  downstream:
  - target: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
    causal_link_type: DIRECT
    description: >-
      Implanted epithelium continues to secrete at its new sites.
  evidence:
  - reference: PMID:39327362
    reference_title: "Reclassification of Appendiceal Mucinous Neoplasms and Associated Pseudomyxoma Peritonei According to the Peritoneal Surface Oncology Group International Consensus: Clinicopathological Reflections of a Two-Center Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ovarian involvement was observed in 43/65 females (66.2%).
    explanation: >-
      Quantifies ovarian involvement in a consecutive series, supporting both the
      distribution claim and the diagnostic trap described here.

- name: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
  role: central_effector
  biological_scale: ORGANISM
  description: >-
    Mucin accumulates faster than the peritoneum can clear it, and it does not stay fluid.
    Progressive sclerosis converts soft mucus into a stiff, adherent mass that encases
    viscera and fixes them to one another and to the abdominal wall.

    The primary literature is explicit that this - not metastasis, not cachexia from tumour
    burden - is the key pathological mechanism and the main cause of death. It is the
    justification for treating mucin itself as a therapeutic target.
  locations:
  - preferred_term: peritoneum
    term:
      id: UBERON:0002358
      label: peritoneum
  downstream:
  - target: Mechanical Visceral Compromise
    causal_link_type: DIRECT
    description: >-
      A stiff, expanding intraperitoneal mass compresses and tethers hollow viscera.
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The mucus sclerosis is the key pathological mechanism in the development of PMP, and
      the main cause of death.
    explanation: >-
      The central claim of this entry, stated by the source in exactly those terms.
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Excessive mucus secretion is also the main cause of death.
    explanation: >-
      Restates the same conclusion about the secreted product rather than the tumour cells.

- name: Mechanical Visceral Compromise
  role: outcome
  biological_scale: ORGANISM
  description: >-
    The clinical endpoint. Progressive abdominal distension, intractable pain, intestinal
    obstruction, organ adhesion and eventually cachexia, as the encased bowel can neither
    move nor absorb.
  locations:
  - preferred_term: peritoneum
    term:
      id: UBERON:0002358
      label: peritoneum
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei
      (PMP), which often leads to significant increase in abdominal circumference,
      intractable abdominal pain, progressive intestinal obstruction, abdominal organ
      adhesions, and cachexia.
    explanation: >-
      Enumerates the mechanical consequences this node collects, and attributes them to the
      secreted mucus.

- name: Intratumoral Hypoxia
  role: amplifier
  biological_scale: TISSUE
  description: >-
    Mucinous nodules that grow beyond their diffusion limit become hypoxic, and hypoxia is
    not a passive endpoint here: HIF-1alpha binds the MUC2 promoter directly and raises MUC2
    transcription.

    That closes a loop. Secreted mucin drives the tissue expansion that creates the hypoxia,
    and the hypoxia drives more mucin. It is the one place in this entry where the chain
    stops being a chain, and it matters practically as well as descriptively - it makes
    HIF-1alpha a target whose inhibition reduces mucinous tumour growth in a xenograft model,
    which is a therapeutic entry point aimed at the secreted product rather than at
    proliferation.
  biological_processes:
  - preferred_term: response to hypoxia
    term:
      id: GO:0001666
      label: response to hypoxia
    modifier: INCREASED
  downstream:
  - target: MUC2 Hypersecretion
    causal_link_type: DIRECT
    description: >-
      HIF-1alpha binding at the MUC2 promoter increases MUC2 transcription, feeding back on
      the node whose product created the hypoxic tissue in the first place.
  evidence:
  - reference: PMID:26589109
    reference_title: "Targeting hypoxia-mediated mucin 2 production as a therapeutic strategy for mucinous tumors."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      In vitro exposure of LS174T cells to hypoxia increased MUC2 messenger RNA (mRNA) and
      protein expression and increased HIF-1α binding to the MUC2 promoter.
    explanation: >-
      The direct promoter-binding result that makes this an amplification edge rather than a
      correlation.
  - reference: PMID:26589109
    reference_title: "Targeting hypoxia-mediated mucin 2 production as a therapeutic strategy for mucinous tumors."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In a murine xenograft model of PMP, chronic oral therapy with BAY 87-2243 inhibited
      mucinous tumor growth and MUC2, HIF-1α expression in the tumor tissue.
    explanation: >-
      Interrupting the loop pharmacologically reduces both MUC2 and tumour growth, which is
      the functional test of the edge.

phenotypes:

- category: Gastrointestinal
  name: Progressive Abdominal Distension
  frequency: VERY_FREQUENT
  description: >-
    The classic presentation, from accumulating mucinous ascites - the appearance that gave
    the disease its colloquial name.
  phenotype_term:
    preferred_term: Abdominal distention
    term:
      id: HP:0003270
      label: Abdominal distention
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei
      (PMP), which often leads to significant increase in abdominal circumference,
      intractable abdominal pain, progressive intestinal obstruction, abdominal organ
      adhesions, and cachexia.
    explanation: >-
      Names increased abdominal circumference as the most prominent feature; the source for
      this and the two phenotypes below.

- category: Gastrointestinal
  name: Intractable Abdominal Pain
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Abdominal pain
    term:
      id: HP:0002027
      label: Abdominal pain
    temporality: CHRONIC
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei
      (PMP), which often leads to significant increase in abdominal circumference,
      intractable abdominal pain, progressive intestinal obstruction, abdominal organ
      adhesions, and cachexia.
    explanation: >-
      Names intractable abdominal pain among the consequences of mucus accumulation.

- category: Gastrointestinal
  name: Progressive Intestinal Obstruction
  frequency: FREQUENT
  severity: SEVERE
  description: >-
    Obstruction here is extrinsic and adhesive - bowel encased and tethered by sclerosing
    mucin - rather than an intraluminal mass, which is why it tends to be diffuse and
    difficult to relieve surgically.
  phenotype_term:
    preferred_term: Intestinal obstruction
    term:
      id: HP:0005214
      label: Intestinal obstruction
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Excessive mucus secretion is the most prominent feature of pseudomyxoma peritonei
      (PMP), which often leads to significant increase in abdominal circumference,
      intractable abdominal pain, progressive intestinal obstruction, abdominal organ
      adhesions, and cachexia.
    explanation: >-
      Names progressive intestinal obstruction and attributes it to mucus accumulation.

- category: Gynecologic
  name: Ovarian Involvement
  frequency: FREQUENT
  diagnostic: true
  description: >-
    Present in about two thirds of women. Almost always secondary seeding from an
    appendiceal primary rather than a primary ovarian tumour - a distinction that changes
    both staging and surgery, and one that the historical literature got wrong.
  phenotype_term:
    preferred_term: Ovarian neoplasm
    term:
      id: HP:0100615
      label: Ovarian neoplasm
  evidence:
  - reference: PMID:39327362
    reference_title: "Reclassification of Appendiceal Mucinous Neoplasms and Associated Pseudomyxoma Peritonei According to the Peritoneal Surface Oncology Group International Consensus: Clinicopathological Reflections of a Two-Center Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ovarian involvement was observed in 43/65 females (66.2%).
    explanation: >-
      The frequency in a consecutive surgical series, which is what supports the FREQUENT
      band.

histopathology:

- name: Mucinous Epithelium in Extracellular Mucin Pools
  description: >-
    Histological grade is what the classification turns on, and in a 155-case series it was
    the only independent prognostic factor for overall survival on multivariate analysis -
    outperforming lymph node metastasis, angiolymphatic invasion, Ki67 index and p53 status,
    all of which looked prognostic on univariate testing.

    The grades run from acellular mucin, through low-grade mucinous carcinoma peritonei, to
    high-grade, to high-grade with signet ring cells. Roughly two thirds of cases are
    low-grade.
  evidence:
  - reference: PMID:31926211
    reference_title: "Pathological prognostic factors of pseudomyxoma peritonei: comprehensive clinicopathological analysis of 155 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      But Multivariate analysis identified only histologic grade was the independent
      prognostic factor for OS.
    explanation: >-
      The multivariate result that makes grade the dominant pathological variable.
  - reference: PMID:31926211
    reference_title: "Pathological prognostic factors of pseudomyxoma peritonei: comprehensive clinicopathological analysis of 155 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The patients included 63.2% (n = 98) low-grade mucinous carcinoma peritonei, 31.6%
      (n = 49) high-grade mucinous carcinoma peritonei and 5.2% (n = 8) high-grade mucinous
      carcinoma peritonei with signet ring cells.
    explanation: >-
      The grade distribution behind the proportions quoted in this entry.

biochemical:

- name: Serum Carcinoembryonic Antigen (CEA)
  notes: >-
    The most-used serum marker in this disease. Preoperative CEA correlates with the
    peritoneal cancer index, which is why it is drawn as part of resectability assessment
    rather than only for follow-up. It has a specific and clinically dangerous failure mode
    recorded below.
  evidence:
  - reference: PMID:27038681
    reference_title: "Expression of CEA, CA19-9, CA125, and EpCAM in pseudomyxoma peritonei."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We found preoperative CEA serum values to correlate with peritoneal cancer index.
    explanation: >-
      Ties the serum measurement to the disease-burden index used for surgical planning.
  - reference: PMID:27038681
    reference_title: "Expression of CEA, CA19-9, CA125, and EpCAM in pseudomyxoma peritonei."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thus, serum CEA measurements did not reflect aggressiveness of these tumors.
    explanation: >-
      PARTIAL because it qualifies the marker rather than supporting it. In the aggressive
      signet-ring cases with nonpolarized CEA staining, serum values were normal and the
      patients died within five years - so a normal CEA does not exclude the worst-prognosis
      subgroup.

- name: Serum CA19-9
  notes: >-
    Used alongside CEA for monitoring. Strongly expressed at tissue level in most tumours,
    with FUT3 mutation explaining the negative and weak-staining cases - so a negative CA19-9
    can reflect the patient's Lewis genotype rather than absence of disease.
  evidence:
  - reference: PMID:27038681
    reference_title: "Expression of CEA, CA19-9, CA125, and EpCAM in pseudomyxoma peritonei."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      CA19-9 showed strong immunopositivity in most of the tumors (91.3%), and mutated enzyme
      FUT3 was demonstrated from the cases showing negative or weak staining.
    explanation: >-
      Gives both the expression frequency and the mechanistic reason some tumours are
      marker-negative.

- name: Serum CA125
  notes: >-
    Historically a source of misdiagnosis as ovarian cancer. Note the dissociation: CA125 is
    infrequently expressed by the tumour cells themselves and comes mostly from adjacent
    non-neoplastic mesothelium, so an elevated serum value reflects peritoneal reaction more
    than tumour mass.
  evidence:
  - reference: PMID:27038681
    reference_title: "Expression of CEA, CA19-9, CA125, and EpCAM in pseudomyxoma peritonei."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      CA125 was infrequently expressed by tumor cells (focal staining in 6.5% of the cases),
      but in most of the cases (79.3%), adjacent nonneoplastic mesothelial cells showed
      immunopositivity.
    explanation: >-
      Establishes the mesothelial rather than tumour-cell origin of the CA125 signal.

- name: Combined Serum Marker Panel
  notes: >-
    CEA, CA125, CA19-9, CA724 and CA242 measured together in serum and ascites. The panel is
    used to judge severity and predict resectability rather than to make the diagnosis.
  evidence:
  - reference: PMID:34733775
    reference_title: "Prognostic Value of CEA, CA19-9, CA125, CA724, and CA242 in Serum and Ascites in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      CEA, CA125, CA19-9, CA724, and CA242 in serum and ascites can be used to judge the
      severity and predict the resectability.
    explanation: >-
      The panel's stated clinical role, from a study designed to evaluate exactly that.

genetic:

- name: KRAS
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  gene_term:
    preferred_term: KRAS
    term:
      id: hgnc:6407
      label: KRAS
  association: >-
    Activating somatic KRAS mutations, predominantly at codon 12, are present in the large
    majority of PMP - 148 of 167 cases (89%) in the largest systematically sequenced series.
    They are somatic drivers in the appendiceal epithelium, not germline predisposition
    alleles.

    Unlike in colorectal cancer, KRAS status has not consistently predicted survival in PMP
    series, so its role here is causal rather than prognostic.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      High frequencies of KRAS and GNAS mutations support the proposed role as driver
      mutations and as potential therapy targets.
    explanation: >-
      The driver claim for both genes, from the series that measured their frequency.

- name: GNAS
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  gene_term:
    preferred_term: GNAS
    term:
      id: hgnc:4392
      label: GNAS
  association: >-
    Activating somatic GNAS mutations at codon 201 are present in 139 of 167 cases (83%) in
    the same series, and co-occur with KRAS far more often than chance.

    GNAS is the mechanistically interesting driver: locking Gs on raises cAMP, and cAMP
    drives mucin secretion. A high GNAS mutation rate in a disease whose lethal agent is
    secreted mucin is not a coincidence, and it is the strongest argument that the
    hypersecretory phenotype is genetically driven rather than incidental.

    Its high frequency in PMP against a low frequency in colorectal adenocarcinoma also
    makes it useful for assigning appendiceal origin.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The frequency of KRAS and GNAS mutations was analyzed in tumor samples from 167
      patients with verified PMP using targeted DNA sequencing and/or droplet digital
      polymerase chain reaction.
    explanation: >-
      The cohort and assay behind the GNAS frequency quoted here.

- name: TP53
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  gene_term:
    preferred_term: TP53
    term:
      id: hgnc:11998
      label: TP53
  association: >-
    TP53 mutation is the grade-associated alteration rather than a universal driver. In a
    114-patient cohort stratified by predominant genomic alteration, half of TP53-mutant
    tumours were WHO grade 3, against 38% of triple-negative, 10% of RAS-mutant and 7% of
    GNAS-mutant tumours - so TP53 marks the aggressive end of a disease whose baseline
    genotype is KRAS and GNAS.
  evidence:
  - reference: PMID:39812318
    reference_title: "TP53 Alterations Are an Independent Adverse Prognostic Indicator in Pseudomyxoma Peritonei of Appendiceal Origin Following Cytoreductive Surgery and Intraperitoneal Chemotherapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Fifty percent of TP53 -mut were WHO grade 3 compared with 38% triple-negative, 10%
      RAS -mut, and 7% GNAS -mut tumors
    explanation: >-
      The grade distribution across molecular groups. Quoted with the source's own irregular
      spacing around the gene names, which is a typesetting artefact of the cached record
      rather than the authors' usage.

- name: BRAF
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  gene_term:
    preferred_term: BRAF
    term:
      id: hgnc:1097
      label: BRAF
  association: >-
    A minority somatic driver - 3 of 35 tumours in the sequenced series - but the one with a
    directly actionable consequence. BRAF-mutant disease is the subgroup for which a licensed
    targeted agent class already exists, which is why it is curated separately from the
    commoner KRAS and GNAS events rather than folded into an "other mutations" line.

    This is the concrete content behind the entry's diagnosis section, which otherwise refers
    to targetable drivers without naming one.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most commonly mutated genes other than KRAS/GNAS were SMAD4 (9/35), PIC3CA (7/35),
      TP53 (6/35), FBXW7 (4/35), and BRAF (3/35)
    explanation: >-
      Gives the BRAF mutation frequency in the sequenced cohort. Note the source's own
      spelling of PIC3CA, which is a typographical error for PIK3CA in the cited text and is
      quoted here unaltered.
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      BRAF mutations, which could be targeted by BRAF inhibitors
    explanation: >-
      The actionability claim that makes this gene worth separating out.

- name: SMAD4
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  gene_term:
    preferred_term: SMAD4
    term:
      id: hgnc:6770
      label: SMAD4
  association: >-
    The most frequent somatic mutation after KRAS and GNAS (9 of 35), and reported as
    associated with inferior outcome. Curated as prognostic rather than mechanistic: this
    entry does not model a SMAD4-specific pathway, and the association is drawn from a single
    series.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the most interesting findings were mutations in SMAD4, which were associated with
      inferior outcome
    explanation: >-
      The prognostic association, stated by the sequencing series itself.

progression:

- phase: Occult appendiceal phase
  notes: >-
    A mucinous neoplasm distends the appendix without peritoneal disease. Often silent, and
    sometimes found incidentally at appendicectomy - the one window in which the disease can
    be prevented rather than treated.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      It is commonly caused by ruptured appendiceal mucinous neoplasms seeding tumor cells
      and mucin into the peritoneal cavity.
    explanation: >-
      Establishes the appendiceal neoplasm as the antecedent lesion that must rupture for
      the peritoneal phase to begin.

- phase: Peritoneal accumulation phase
  notes: >-
    After perforation, mucin accumulates over years. Indolent in low-grade disease, which is
    why patients often present late with gross distension rather than early with pain.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Pseudomyxoma peritonei (PMP) is a rare, progressive, but generally slow-growing
      abdominal cancer with an incidence rate of 3.2 people per million per year
    explanation: >-
      Characterises the tempo of this phase as progressive but slow-growing.

- phase: Mechanical decompensation
  notes: >-
    Sclerosed mucin encases the viscera, producing obstruction, adhesion and cachexia.
    Survival at this stage is grade-dependent: five-year overall survival runs from 100% for
    acellular mucin down to 20% for disease with signet ring cells.
  evidence:
  - reference: PMID:39327362
    reference_title: "Reclassification of Appendiceal Mucinous Neoplasms and Associated Pseudomyxoma Peritonei According to the Peritoneal Surface Oncology Group International Consensus: Clinicopathological Reflections of a Two-Center Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Median OS was 13.8 years, and 5-year OS rates were 100%, 74.4%, 44.4%, and 20% for
      acellular mucin, low-grade PMP, high-grade PMP and PMP-SRC, respectively
    explanation: >-
      The grade-stratified survival figures quoted here.

diagnosis:

- name: Histopathological Grading by PSOGI Classification
  description: >-
    Grading is the diagnostic act that matters, because it is the only independent predictor
    of survival. The scheme separates acellular mucin, low-grade PMP, high-grade PMP and
    PMP with signet ring cells, and the survival separation between those groups is wide.

    Grade of the peritoneal disease is not always the grade of the primary: in 13% of a
    contemporary series the appendiceal neoplasm and its matching PMP were graded
    differently, so the peritoneal disease has to be graded on its own material.
  evidence:
  - reference: PMID:39327362
    reference_title: "Reclassification of Appendiceal Mucinous Neoplasms and Associated Pseudomyxoma Peritonei According to the Peritoneal Surface Oncology Group International Consensus: Clinicopathological Reflections of a Two-Center Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Median OS was 13.8 years, and 5-year OS rates were 100%, 74.4%, 44.4%, and 20% for
      acellular mucin, low-grade PMP, high-grade PMP and PMP-SRC, respectively
    explanation: >-
      The survival separation between grades, which is what makes grading the decisive
      diagnostic step.
  - reference: PMID:31926211
    reference_title: "Pathological prognostic factors of pseudomyxoma peritonei: comprehensive clinicopathological analysis of 155 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      But Multivariate analysis identified only histologic grade was the independent
      prognostic factor for OS.
    explanation: >-
      Establishes grade as the only variable surviving multivariate adjustment.

- name: KRAS and GNAS Mutation Testing
  description: >-
    Molecular testing serves two purposes. It supports appendiceal origin, since the
    KRAS-plus-GNAS pattern is uncommon in colorectal adenocarcinoma. And it identifies
    targetable drivers as agents against them become available.

    There is a practical trap: peritoneal tumour samples have low cellularity, which is the
    main reason reported mutation frequencies have varied so widely. Testing the primary
    appendiceal tumour instead raises the detection rate.
  evidence:
  - reference: PMID:41868810
    reference_title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The frequency of KRAS and GNAS mutations was analyzed in tumor samples from 167
      patients with verified PMP using targeted DNA sequencing and/or droplet digital
      polymerase chain reaction.
    explanation: >-
      The assay approach, including the sensitive digital PCR method used because of low
      tumour cellularity.

treatments:

- name: Cytoreductive Surgery
  therapeutic_modality: SURGERY
  description: >-
    Surgical removal of all visible tumour and mucin, typically with peritonectomy and
    resection of involved viscera. It is the definitive treatment, and it works because the
    disease sits on peritoneal surfaces rather than infiltrating through them.

    Completeness of cytoreduction is the operative variable that matters, which is why the
    procedure is centralised to high-volume units.
  treatment_term:
    preferred_term: cytoreductive surgery
    term:
      id: NCIT:C132068
      label: Cytoreductive Surgery
  target_mechanisms:
  - target: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
    description: >-
      Removes the accumulated mucin and the implanted epithelium producing it, addressing
      both the product and its source.
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy
      (HIPEC) is the recommended treatment for PMP.
    explanation: >-
      Establishes the combined procedure as recommended treatment; the source for this and
      the HIPEC entry below.

- name: Hyperthermic Intraperitoneal Chemotherapy
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Heated chemotherapy perfused through the peritoneal cavity immediately after
    cytoreduction, to treat residual microscopic disease on surfaces that surgery cannot
    clear. Given regionally rather than systemically because the disease is confined to the
    peritoneal compartment.

    Recurrence remains frequent even after complete cytoreduction with HIPEC, which is what
    motivates the mucolytic approach below.
  treatment_term:
    preferred_term: hyperthermic intraperitoneal chemotherapy
    term:
      id: NCIT:C91835
      label: Hyperthermic Intraperitoneal Chemotherapy
    therapeutic_agent:
    - preferred_term: mitomycin C
      term:
        id: CHEBI:27504
        label: mitomycin C
    - preferred_term: oxaliplatin
      term:
        id: CHEBI:31941
        label: oxaliplatin
  target_mechanisms:
  - target: Peritoneal Redistribution and Implantation
    description: >-
      Targets residual implanted epithelium left on peritoneal surfaces after cytoreduction.
  evidence:
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy
      (HIPEC) is the recommended treatment for PMP.
    explanation: >-
      Names HIPEC as part of the recommended combined treatment.
  - reference: PMID:34703312
    reference_title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      However, recurrence is frequently observed even after CRS and HIPEC, presenting
      similar clinical manifestations.
    explanation: >-
      PARTIAL because it qualifies the treatment rather than supporting it: recurrence is
      frequent despite the recommended regimen.

- name: Mucolytic Therapy (investigational)
  therapeutic_modality: OTHER
  description: >-
    Dissolving mucin directly, rather than resecting it or killing the cells that make it.
    The rationale follows from this entry's central claim: if the secreted product is what
    kills, then degrading it is a rational target in its own right.

    Approaches under investigation act on mucin O-glycosylation - the glycan that carries
    most of the molecule's mass and all of its viscoelasticity - including inhibitors of the
    glycosyltransferases that build it and nucleotide-sugar analogues that starve them of
    substrate.

    Investigational. No clinical outcome data exist; the literature to date is review and
    preclinical.
  target_mechanisms:
  - target: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
    description: >-
      Acts on the accumulated mucin itself, which is the node this entry identifies as the
      cause of death.
  evidence:
  - reference: PMID:41947779
    reference_title: "Mucin O-Glycosylation and Mucolytic Therapies in Pseudomyxoma Peritonei: Literature Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Effective mucolytic therapy can greatly improve the efficacy of cytoreductive surgery
      + hyperthermic intraperitoneal chemotherapy, alleviate symptoms and improve prognosis
      for pseudomyxoma peritonei (PMP) patients.
    explanation: >-
      PARTIAL because the source states the expected benefit of effective mucolysis as a
      premise for review rather than reporting an achieved clinical result.
  - reference: PMID:41947779
    reference_title: "Mucin O-Glycosylation and Mucolytic Therapies in Pseudomyxoma Peritonei: Literature Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The main components of PMP mucus are highly O-glycosylated proteins called mucins.
    explanation: >-
      Establishes O-glycosylation as the property these approaches target.

- name: Systemic Chemotherapy
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Oxaliplatin/5-fluorouracil/leucovorin-type regimens given systemically, for disease that
    cannot be completely cytoreduced or that has recurred beyond further surgery.

    This is second-line by necessity rather than by preference. The compartment argument that
    makes intraperitoneal delivery attractive works against systemic delivery: a
    poorly vascularised mucin lake is a difficult target for a drug arriving through the
    blood, and response rates in this histology are correspondingly modest. It is curated
    here because it is what patients with unresectable disease actually receive.
  treatment_term:
    preferred_term: chemotherapy
    term:
      id: NCIT:C15632
      label: Chemotherapy
    therapeutic_agent:
    - preferred_term: oxaliplatin
      term:
        id: CHEBI:31941
        label: oxaliplatin
    - preferred_term: fluorouracil
      term:
        id: CHEBI:46345
        label: 5-fluorouracil
  target_mechanisms:
  - target: Peritoneal Redistribution and Implantation
    description: >-
      Directed at implanted epithelium that cytoreduction cannot reach or has left behind.
  evidence:
  - reference: clinicaltrials:NCT00352755
    reference_title: "A Phase II Study of Surgical Debulking With Peritonectomy and Biweekly Intraperitoneal 5FU With Systemic Oxaliplatin/5FU/Leucovorin in Patients With Pseudomyxoma Peritonei or Peritoneal Carcinomatosis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Patients with peritoneal carcinomatosis or pseudomyxoma peritonei will undergo
      debulking surgery with peritonectomy and placement of adhesive barrier film followed
      by repeated delayed intraperitoneal chemotherapy with 5FU with systemic
      oxaliplatin-based chemotherapy on a biweekly schedule.
    explanation: >-
      A Phase II protocol administering systemic oxaliplatin/5FU/leucovorin in this disease,
      establishing the regimen as one given to these patients.

- name: Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC)
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Low-dose chemotherapy delivered into the abdomen as a pressurized aerosol at laparoscopy,
    for unresectable or recurrent disease. The rationale is distribution rather than dose:
    an aerosol reaches peritoneal surfaces that a liquid instillation pools away from, which
    is the same compartment logic behind HIPEC applied to patients who cannot have surgery.

    Evidence in this disease specifically is thin - a single case report - and it is curated
    at that strength rather than as an established option.
  treatment_term:
    preferred_term: chemotherapy
    term:
      id: NCIT:C15632
      label: Chemotherapy
    therapeutic_agent:
    - preferred_term: cisplatin
      term:
        id: CHEBI:27899
        label: cisplatin
    - preferred_term: doxorubicin
      term:
        id: CHEBI:28748
        label: doxorubicin
  target_mechanisms:
  - target: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
    description: >-
      Aimed at the accumulating peritoneal disease in patients who are not cytoreduction
      candidates.
  evidence:
  - reference: PMID:26076000
    reference_title: "Pressurized intraperitoneal aerosol chemotherapy (PIPAC) with cisplatin and doxorubicin in a woman with pseudomyxoma peritonei: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PIPAC achieved clinical and histological disease remission.
    explanation: >-
      The reported outcome. A single case, which is why this treatment is described as
      investigational rather than standard.
  notes: >-
    Evidence strength is one case report. Recorded because it is the only aerosol-delivery
    option reported in this disease, not because it is established.

clinical_trials:

- name: NCT01946854
  phase: NOT_APPLICABLE
  status: ACTIVE_NOT_RECRUITING
  description: >-
    Randomized crossover trial of systemic chemotherapy in metastatic well-differentiated
    mucinous appendiceal adenocarcinoma with pseudomyxoma peritonei. Its premise is the
    open question this entry's treatment section reflects - whether systemic chemotherapy
    affects this histology at all.
  evidence:
  - reference: clinicaltrials:NCT01946854
    reference_title: "A Randomized Crossover Trial of Systemic Chemotherapy in Patients With Metastatic Well-Differentiated Mucinous Appendiceal Adenocarcinomas With Pseudomyxoma Peritonei"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Appendiceal cancer is a rare disease that does not cause many symptoms. As such,
      doctors are not sure if chemotherapy actually has an effect on the disease.
    explanation: >-
      The registration record states the uncertainty the trial was designed to resolve.

- name: NCT00352755
  phase: PHASE_II
  status: TERMINATED
  description: >-
    Phase II study of debulking with peritonectomy plus biweekly intraperitoneal 5-FU and
    systemic oxaliplatin/5-FU/leucovorin. Terminated.
  evidence:
  - reference: clinicaltrials:NCT00352755
    reference_title: "A Phase II Study of Surgical Debulking With Peritonectomy and Biweekly Intraperitoneal 5FU With Systemic Oxaliplatin/5FU/Leucovorin in Patients With Pseudomyxoma Peritonei or Peritoneal Carcinomatosis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This formal Phase II study is planned to determine the safety, toxicities and survival
      of patients with peritoneal carcinomatosis and pseudomyxoma peritonei treated with
      this regimen.
    explanation: >-
      States the trial's phase, population and endpoints.

animal_models:

- name: PMP patient-derived xenograft (PDX) mouse
  species: Mouse
  publication: PMID:26833741
  description: >-
    Serial engraftment of patient PMP tumour into immunocompromised mice. Both low-grade and
    high-grade donors were engrafted, and the resulting tumours were histopathologically
    similar to human PMP.

    The model's declared purpose is the tumour-stroma interface rather than the tumour cells
    alone, and its design makes that tractable in an unusual way: the tumour is human and the
    stroma is murine, so the species of a given cytokine identifies its cellular source.
  modeled_mechanisms:
  - target: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces the peritoneal mucinous tumour and its inflammatory microenvironment, which
      is the compartment where this node's fibrosis and sclerosis develop.
    limitations: >-
      The inflammatory environment is reproduced but not faithfully: IL-6 and IL-8/KC/MIP2
      differed significantly between human and PDX ascites, and the cytokines were secreted
      mostly by murine stromal cells rather than by the human tumour cells. Any inference
      about human tumour-cell signalling drawn from this model is therefore indirect.
    readouts:
    - name: Ascites cytokine profile
      target: Progressive Intraperitoneal Mucin Accumulation and Sclerosis
      direction: ALTERED
      interpretation: >-
        Cytokines elevated in human PMP were also elevated in PDX ascites, establishing the
        model's inflammatory phenotype while the species differences bound its fidelity.
      evidence:
      - reference: PMID:26833741
        reference_title: "Patient-derived xenograft mouse models of pseudomyxoma peritonei recapitulate the human inflammatory tumor microenvironment."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Cytokines previously shown to be elevated in human PMP were also elevated in PDX
          ascites.
        explanation: >-
          The measurement establishing that the model reproduces the inflammatory milieu.
    evidence:
    - reference: PMID:26833741
      reference_title: "Patient-derived xenograft mouse models of pseudomyxoma peritonei recapitulate the human inflammatory tumor microenvironment."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        PDX mouse models of low- and high-grade PMP were generated and were of a similar
        histopathology as human PMP.
      explanation: >-
        Establishes that the model reproduces the disease's histopathology across both grade
        tiers, which is what makes it informative for this node.

- name: Intraperitoneal murine xenograft of PMP (HIF-1α inhibition)
  species: Mouse
  publication: PMID:26589109
  description: >-
    An intraperitoneal xenograft used to test whether interrupting the hypoxia-MUC2 loop
    reduces mucinous tumour growth. Curated because it is the experimental support for the
    amplification edge in the pathophysiology section.
  modeled_mechanisms:
  - target: Intratumoral Hypoxia
    relationship: RESCUES
    fidelity: MODERATE
    description: >-
      Pharmacological HIF-1α inhibition in this model reduced both MUC2 expression and
      mucinous tumour growth, testing the amplification loop by interrupting it.
    limitations: >-
      A xenograft in immunocompromised mice, so the immune contribution to the peritoneal
      environment is absent; and the readout is tumour growth rather than the mechanical
      visceral compromise that determines outcome in patients.
    readouts:
    - name: Mucinous tumour growth under HIF-1α inhibition
      target: Intratumoral Hypoxia
      direction: DECREASED
      interpretation: >-
        Growth and MUC2/HIF-1α expression both fell under chronic oral BAY 87-2243.
      evidence:
      - reference: PMID:26589109
        reference_title: "Targeting hypoxia-mediated mucin 2 production as a therapeutic strategy for mucinous tumors."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          In a murine xenograft model of PMP, chronic oral therapy with BAY 87-2243 inhibited
          mucinous tumor growth and MUC2, HIF-1α expression in the tumor tissue.
        explanation: >-
          The in vivo result behind the therapeutic rationale for targeting this loop.

discussions:

- discussion_id: mismatch_pdx_stromal_species
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - animal_models#Mouse
  - pathophysiology#Progressive Intraperitoneal Mucin Accumulation and Sclerosis
  prompt: >-
    In the PDX model, does the murine origin of the inflammatory signal limit what can be
    concluded about the human peritoneal microenvironment that drives fibrosis and sclerosis?
  rationale: >-
    This is not a case of absent evidence - the model exists and reproduces both the
    histopathology and an elevated ascites cytokine profile. The open question is what that
    evidence licenses. The cytokines were secreted mostly by mouse-derived stromal cells
    rather than by human tumour cells, and IL-6 and IL-8/KC/MIP2 differed significantly
    between human and PDX ascites.

    So the model demonstrates that human PMP tumour cells can provoke an inflammatory stromal
    response, and lets that response be attributed to stroma by species. It does not
    establish that the human stromal response has the same composition. Because this entry
    treats mucin accumulation with sclerosis as the node that produces clinical harm, and
    fibrosis is stroma-driven, the gap sits directly under a load-bearing claim.
  proposed_experiments:
  - experiment_id: compare_human_pdx_stromal_cytokines
    name: Species-resolved cytokine profiling of human versus PDX PMP ascites
    description: >-
      Paired profiling of human PMP ascites and matched PDX ascites with species-resolved
      assignment of each cytokine to human tumour or murine stromal origin, to quantify which
      components of the human inflammatory milieu the model reproduces and which it replaces.
    would_support:
    - pathophysiology#Progressive Intraperitoneal Mucin Accumulation and Sclerosis
    supporting_outcome:
    - >-
      Species-resolved profiling shows the murine stromal response reproduces the dominant
      profibrotic cytokines of human PMP, supporting use of the model for fibrosis studies.
    refuting_outcome:
    - >-
      The murine response diverges on the profibrotic axis specifically, indicating the model
      is informative for tumour-cell behaviour but not for the sclerosis this node describes.

- discussion_id: gap_secretion_versus_proliferation_target
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#MUC2 Hypersecretion
  - treatments#Mucolytic Therapy (investigational)
  prompt: >-
    Would suppressing mucin secretion control this disease better than killing the cells
    that secrete it?
  rationale: >-
    The entry's mechanism says the lethal agent is the secreted product, and the driver
    genetics agree - GNAS mutation in 83% of cases acts through cAMP on precisely the
    secretory phenotype. Yet every established treatment targets cells: resect them, or
    perfuse them with cytotoxic drug. Recurrence after complete cytoreduction with HIPEC
    remains frequent.

    Nobody has tested whether pharmacologically suppressing secretion, as opposed to
    dissolving mucin already deposited, changes the course. The two are different
    interventions with different windows: mucolysis treats accumulated disease, secretion
    blockade would prevent accumulation, and only the second could plausibly be given long
    term after cytoreduction.

    The experiment is tractable because the pathway is known and druggable at several
    points, and because low-grade PMP is indolent enough that a secretion-suppressing agent
    would have time to show an effect.
  proposed_experiments:
  - experiment_id: pmp_secretion_blockade_vs_cytotoxicity
    name: cAMP-pathway secretion blockade versus cytotoxic control in GNAS-mutant PMP models
    description: >-
      In patient-derived GNAS-mutant PMP models, compare mucin output and disease
      accumulation under cAMP-pathway blockade against a cytotoxic comparator matched for
      effect on cell viability, separating suppression of secretion from killing of
      secreting cells.
    would_support:
    - pathophysiology#MUC2 Hypersecretion
    supporting_outcome:
    - >-
      Secretion blockade reduces mucin accumulation at doses that do not reduce viable
      tumour cell number, establishing secretion as an independently targetable step.
    refuting_outcome:
    - >-
      Mucin accumulation tracks tumour cell number regardless of pathway blockade, which
      would make secretion a read-out of tumour burden rather than a separate target and
      redirect effort back to cytoreduction.

- discussion_id: gap_grade_discordance
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - diagnosis#Histopathological Grading by PSOGI Classification
  - histopathology#Mucinous Epithelium in Extracellular Mucin Pools
  prompt: >-
    When the appendiceal primary and the peritoneal disease are graded differently, which
    grade predicts outcome?
  rationale: >-
    Grade is the only independent predictor of survival, and in 13% of a contemporary series
    the primary neoplasm and its matching peritoneal disease did not carry the same grade.
    Those two facts together mean that in one case in eight the prognostic variable depends
    on which specimen was graded, and the literature does not say which one to use.

    It is a directly consequential gap: grade drives the decision to offer or withhold a
    major operation with substantial morbidity.
  proposed_experiments:
  - experiment_id: pmp_discordant_grade_outcome
    name: Outcome analysis of grade-discordant appendiceal and peritoneal specimens
    description: >-
      In a multi-centre cohort with both primary and peritoneal specimens graded
      independently, model overall survival against primary grade, peritoneal grade and the
      higher of the two, and compare their predictive performance in the discordant subset.
    would_support:
    - diagnosis#Histopathological Grading by PSOGI Classification
    supporting_outcome:
    - >-
      Peritoneal grade predicts survival better than primary grade in discordant cases,
      which would make grading of peritoneal material the standard and settle the question.
    refuting_outcome:
    - >-
      Neither specimen predicts better than the higher of the two, which would argue for
      taking the worst grade found on any material and would simplify the decision rule.

notes: >-
  Scope. Pseudomyxoma peritonei is a syndrome defined by peritoneal mucinous disease, not by
  a single histological entity, and this entry treats it that way. Its antecedent lesion -
  the appendiceal mucinous neoplasm - is a distinct concept and is named as a parent rather
  than folded in.

  Ovarian origin. Older literature described primary ovarian mucinous tumours as a common
  source of PMP. That has been revised: most ovarian involvement is secondary seeding from
  an appendiceal primary, distinguishable by immunohistochemistry. This entry curates
  ovarian involvement as a site of implantation, and the historical misattribution is
  flagged because it is still the commonest way this disease is misclassified.

  Percentages in prose. The KRAS and GNAS frequencies (89% and 83% of 167 cases) appear in
  this entry's descriptions but not as quoted snippets. The sentence carrying them in the
  cached record uses narrow no-break spaces before each percent sign, so quoting it exactly
  would embed invisible characters in the KB. The cohort and the driver conclusion are
  quoted instead, and the numbers are reported in prose from the same sentence.

  Terminology. The disease has accumulated several naming systems - DPAM and PMCA in the
  older Ronnett scheme, low-grade and high-grade mucinous carcinoma peritonei in the WHO and
  PSOGI schemes. Grade names in this entry follow the source being cited at that point rather
  than being harmonised, because the survival figures are only meaningful against the scheme
  that generated them.

references:
- reference: PMID:41868810
  title: "High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies."
- reference: PMID:39327362
  title: "Reclassification of Appendiceal Mucinous Neoplasms and Associated Pseudomyxoma Peritonei According to the Peritoneal Surface Oncology Group International Consensus: Clinicopathological Reflections of a Two-Center Cohort Study."
- reference: PMID:34703312
  title: "The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei."
- reference: PMID:31926211
  title: "Pathological prognostic factors of pseudomyxoma peritonei: comprehensive clinicopathological analysis of 155 cases."
- reference: PMID:39812318
  title: "TP53 Alterations Are an Independent Adverse Prognostic Indicator in Pseudomyxoma Peritonei of Appendiceal Origin Following Cytoreductive Surgery and Intraperitoneal Chemotherapy."
- reference: PMID:41947779
  title: "Mucin O-Glycosylation and Mucolytic Therapies in Pseudomyxoma Peritonei: Literature Review."
📚

References & Deep Research

References

6
PMID:41868810
High prevalence of KRAS and GNAS mutations in pseudomyxoma peritonei underscores opportunities for targeted therapeutic strategies.
No top-level findings curated for this source.
PMID:39327362
Reclassification of Appendiceal Mucinous Neoplasms and Associated Pseudomyxoma Peritonei According to the Peritoneal Surface Oncology Group International Consensus: Clinicopathological Reflections of a Two-Center Cohort Study.
No top-level findings curated for this source.
PMID:34703312
The Biological Synthesis and the Function of Mucin 2 in Pseudomyxoma Peritonei.
No top-level findings curated for this source.
PMID:31926211
Pathological prognostic factors of pseudomyxoma peritonei: comprehensive clinicopathological analysis of 155 cases.
No top-level findings curated for this source.
PMID:39812318
TP53 Alterations Are an Independent Adverse Prognostic Indicator in Pseudomyxoma Peritonei of Appendiceal Origin Following Cytoreductive Surgery and Intraperitoneal Chemotherapy.
No top-level findings curated for this source.
PMID:41947779
Mucin O-Glycosylation and Mucolytic Therapies in Pseudomyxoma Peritonei: Literature Review.
No top-level findings curated for this source.

Deep Research

1
Claude Code ▸
Pseudomyxoma Peritonei: Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 37 citations 2026-08-26T16:19:53.115038

Pseudomyxoma Peritonei: Comprehensive Research Report

1. Disease Information

Overview. Pseudomyxoma peritonei (PMP) is a rare, clinically distinctive syndrome of progressive intraperitoneal mucin accumulation ("jelly belly") caused, in the overwhelming majority of cases, by a mucinous neoplasm that perforates the appendix and seeds mucin-producing epithelial cells across the peritoneal surfaces. It is best conceptualized not as a single histologic entity but as a clinical syndrome with a spectrum of underlying pathology ranging from acellular mucin to low-grade and high-grade mucinous carcinoma peritonei. The 2019 PSOGI review frames it as "a clinical entity characterised by the presence of mucinous ascites, omental cake, peritoneal implants and possibly ovarian involvement" (Pathophysiology and classification of pseudomyxoma peritonei, PMC6386305).

Key identifiers: - Orphanet: ORPHA:26790 (Orphanet; OLS) - MONDO: MONDO:0017048 - ICD-10-CM: C78.6 (Secondary malignant neoplasm of retroperitoneum and peritoneum — used when coding the peritoneal spread; some coders use the appendiceal primary code) (icd10data.com) - ICD-9-CM: 197.6 - ICD-O morphology code: 8480 (mucinous adenocarcinoma) - GARD/NORD entry (NIH rare disease portal): GARD 7488; NORD - OMIM: No dedicated OMIM phenotype MIM number exists — PMP is treated as a sporadic neoplastic syndrome rather than a classic Mendelian phenotype, consistent with its overwhelmingly somatic mutational origin.

Synonyms/alternative names: "jelly belly"; disseminated peritoneal adenomucinosis (DPAM, when low-grade); peritoneal mucinous carcinomatosis (PMCA, when high-grade); mucinous carcinoma peritonei; PMP syndrome.

Data derivation: The evidence base is drawn almost entirely from aggregated disease-level resources — retrospective single- and multi-institutional surgical cohorts (typically from specialist national referral centers, since PMP is centralized to a handful of high-volume units), pooled national/regional epidemiologic registries (e.g., a nationwide Chinese urban cohort), and increasingly targeted/whole-exome sequencing panels across pooled tumor collections — rather than individual EHR-level data, reflecting the rarity and referral-center concentration of the disease.

2. Etiology

Primary causal mechanism. PMP is, in essence, a mechanistic rather than classically genetic or infectious disease: an epithelial neoplasm — almost always a low-grade appendiceal mucinous neoplasm (LAMN), less commonly a high-grade appendiceal mucinous adenocarcinoma — obstructs and distends the appendiceal lumen, perforates the appendiceal wall, and disseminates mucin-secreting epithelial cells onto peritoneal surfaces. A population-based study found the primary site identifiable in 68% of cases, dominated by the appendix in 82% of those (Smeenk et al., PMID: 17524597). Non-appendiceal primaries (ovary, urachus, colon, pancreas, gallbladder) are rare and the historical belief that ovarian mucinous tumors were a common primary source has been revised — most "ovarian" PMP is now understood to be secondary/metastatic from an appendiceal primary via immunohistochemical concordance (MUC2, CK20, CDX2 positivity favoring appendiceal origin over CK7-positive primary ovarian mucinous tumors).

Genetic causal factors (somatic driver mutations): - KRAS — mutated in 58–100% of sequenced cases depending on cohort and methodology, predominantly at codon 12 (Pathophysiology review, PMC6386305; High prevalence of KRAS/GNAS mutations, PMID: 41868810) - GNAS — activating mutations (predominantly R201H/R201C) reported in 12–100% of cases depending on grade and cohort, thought to drive the mucin-hypersecretory phenotype via cAMP signaling (Nummela et al. molecular profiles study, PMC5123786) - TP53 — more prevalent in high-grade disease (17–31% vs. 4–7% in low-grade, p=0.012–0.005), associated with female sex and worse survival - SMAD4, PIK3CA, BRAF, APC, ERBB4, BAP1, TGFBR2, ATM, FAT4 — minority alterations (1–10% each), with BRAF V600E enriched specifically in high-grade signet-ring-cell disease - A 223-case targeted sequencing study found GNAS and KRAS mutated in 42% each, with strong co-occurrence (adjusted p=2.72×10⁻²¹, odds ratio 22.3), and that mutation in either gene predicted worse survival (combined HR 1.87, p=0.004) (Targeted Genetic Sequencing of 223 Cases, PMID: 39435876 / PMC11494485) - This genetic profile is notably distinct from colorectal adenocarcinoma: PMP shows markedly higher KRAS/GNAS rates but lower TP53/PI3K-AKT pathway involvement.

Risk factors. No established environmental, occupational, dietary, infectious, or lifestyle risk factors have been identified for PMP itself. NORD explicitly states "there are no genetic, familial, or environmental factors known to cause this disorder" beyond the mechanical event of LAMN perforation (NORD). This distinguishes PMP sharply from peritoneal mesothelioma (which shares a similar clinical/radiologic appearance but has well-established asbestos/smoking risk associations) — a distinction that matters diagnostically since the two can be difficult to distinguish radiologically and pathologically. The dominant "risk factor" is simply the presence of a perforated (or perforation-prone) LAMN — perforation status is the single strongest determinant of progression to PMP.

Protective factors. None specifically established; early diagnosis and resection of an appendiceal mucinous neoplasm before perforation is the only known "protective" intervention, effectively preventing PMP rather than modifying an established risk.

Familial/hereditary clustering. True hereditary PMP is exceptionally rare, with only a handful of reported kindreds: - A father-daughter pair with appendiceal mucinous tumors and PMP underwent germline whole-exome sequencing; 15 novel shared variants across 15 genes were identified, including a nonsense mutation in REEP5, correlated against regions of tumor loss of heterozygosity (Germline WES family study, PMC7195761) - A separate first-degree relative pair shared germline RAD51C and FH variants alongside somatic KRAS/GNAS/TSC1 mutations (King et al., Clinical Case Reports) - Only two prior familial kindreds have otherwise been documented in the literature (monozygotic twin brothers; a brother-sister pair), underscoring that these findings are exploratory leads, not established Mendelian etiology.

Gene-environment interactions. None described in the literature; the mechanistic pathway is essentially cell-autonomous (somatic driver mutation → epithelial proliferation/mucin hypersecretion → mechanical perforation → peritoneal seeding) with no identified environmental modifier.

3. Phenotypes

PMP phenotypes are predominantly mass-effect/obstructive and laboratory (tumor marker) findings rather than classic syndromic HPO-style malformations, consistent with its acquired/neoplastic nature.

Symptoms and clinical signs (suggested HP terms in parentheses): - Progressive abdominal distension/"jelly belly" — the classic presenting sign, from mucinous ascites (HP:0003270 Abdominal distention) - Abdominal pain/discomfort (HP:0002027 Abdominal pain) - Bloating, early satiety, loss of appetite (HP:0004396 Abdominal bloating; HP:0004395 Decreased appetite) - New-onset or worsening inguinal hernia in men, from raised intra-abdominal pressure (HP:0000023 Inguinal hernia) - Palpable ovarian/pelvic mass in women — historically misattributed to primary ovarian neoplasm (HP:0100615 Ovarian neoplasm) - Bowel obstruction in advanced disease (HP:0025144 Bowel obstruction) - Dyspnea/shortness of breath from diaphragmatic compression by ascites (HP:0002094 Dyspnea) - Weight loss, constipation, urinary symptoms — less common - Incidental discovery at appendectomy or unrelated abdominal surgery/imaging — a substantial minority present asymptomatically

Characteristics: - Onset: Adult-onset; commonly diagnosed in the 5th–6th decade, though the underlying LAMN may be indolent for years before perforation/diagnosis - Progression: Classically slow/indolent, especially in low-grade (DPAM) disease, which can smolder over years; high-grade disease progresses more rapidly - Course: Often initially asymptomatic or mimicking irritable bowel syndrome, then progressive distension, then mechanical bowel/organ compromise if untreated — "tumors provoke fibrosis of surrounding tissues and impede digestion and organ function... ultimately destroy function of colon, small intestine, stomach, or other intra-abdominal organs" if untreated - Frequency: Population estimates suggest 68% have an identifiable primary (82% appendiceal); ovarian involvement is common in women due to secondary seeding rather than primary origin

Laboratory abnormalities (biomarkers): - Elevated CEA — in ~75% of patients preoperatively - Elevated CA19-9 — in ~58% - Elevated CA-125 — commonly elevated, historically contributing to misdiagnosis as ovarian cancer - Elevated tumor markers correlate with higher Peritoneal Cancer Index (PCI), higher risk of incomplete cytoreduction, longer hospital stay, and worse prognosis (Prognostic Value of CEA, CA19-9, CA125, CA724, CA242, PMID: 34733775)

Quality of life impact: Progressive abdominal distension, early satiety, and mechanical compression significantly impair daily functioning; disease recurrence after surgery and the morbidity of CRS-HIPEC itself (a major, high-morbidity operation) both substantially affect QOL, though structured EQ-5D/SF-36 PMP-specific QOL data are sparse in the literature relative to more common cancers.

4. Genetic/Molecular Information

Causal/driver genes (see Etiology for frequencies): KRAS (HGNC:6407), GNAS (HGNC:4392), TP53 (HGNC:11998), SMAD4 (HGNC:6770), PIK3CA (HGNC:8975), BRAF (HGNC:1097), APC (HGNC:583), ERBB4 (HGNC:3432), BAP1 (HGNC:950), TGFBR2 (HGNC:11772).

Variant classification/type: - KRAS: Missense hotspot mutations, predominantly codon 12 (G12D most common — reported at 63% of KRAS-mutant preclinical models; also G12V, G12C, A146, G13C) — activating, gain-of-function - GNAS: Missense hotspot mutations at codon 201 (R201H ~86%, R201C ~14% in one preclinical series) — activating (constitutive Gsα/cAMP signaling), gain-of-function - BRAF: V600E — enriched in high-grade signet-ring-cell tumors, activating - TP53: Predominantly loss-of-function/dominant-negative missense and truncating variants, more common in high-grade disease

Somatic vs. germline: The overwhelming majority of PMP-driving mutations are somatic. Germline predisposition variants have only been reported in isolated familial case reports (REEP5, RAD51C, FH — see Etiology) and are not established as recurrent causal loci.

Population allele frequency databases: Not directly applicable, since these are somatic cancer driver mutations rather than population polymorphisms; standard population databases (gnomAD, 1000 Genomes) are not the relevant reference for KRAS/GNAS hotspot variants in this context (COSMIC is more relevant for somatic frequency).

Functional consequences: - KRAS mutation → constitutive RAS/MAPK pathway activation; in PMP specifically, KRAS has been proposed to induce GM-CSF expression contributing to the immunosuppressive tumor microenvironment - GNAS mutation → constitutive Gsα activation → elevated cAMP → enhanced A2AR (adenosine A2A receptor) signaling and mucin hypersecretion — a mechanism distinct from and potentially synergistic with KRAS-driven effects (A2AR Expression and Immunosuppressive Environment in PMP, doi:10.3390/biomedicines11072049) - The GNAS-KRAS co-mutation signature is a defining molecular feature that distinguishes PMP from colorectal adenocarcinoma, where GNAS mutations are rare

Molecular subtype correlation: Molecular profiling shows GNAS mutation rates as high as 63–100% in low-grade disease with "no marked difference" reported between grades in some series, while TP53 is clearly grade-associated (enriched in high-grade). KRAS mutation status, unlike in colorectal cancer, does not predict survival independently in most series, though the newer 223-case cohort found both KRAS (HR 1.72) and GNAS (HR 1.48) individually prognostic for worse survival, with combined mutation carrying the highest hazard (HR 1.87) (PMC11494485).

Epigenetic information: Limited direct PMP-specific epigenetic data exist; hypoxia-driven transcriptional regulation of mucin genes (see Mechanism section) represents the best-characterized regulatory layer, mediated through HIF-1α binding to the MUC2 promoter rather than classical DNA methylation/histone studies.

Chromosomal abnormalities: Not a defining feature; PMP is not classically associated with recurrent aneuploidy, translocations, or copy-number syndromes in the way many solid tumors are — the driver landscape is dominated by point mutations (KRAS/GNAS) rather than structural variation.

5. Environmental Information

As noted above, no established environmental toxin, occupational exposure, radiation, dietary, or lifestyle factor has been linked to PMP causation. No infectious agent has been implicated. This is a notable negative finding worth stating explicitly for KB purposes: PMP has no known ECTO-bindable exposure etiology — its causal chain begins with somatic mutation and mechanical perforation, not exogenous exposure.

6. Mechanism / Pathophysiology

Causal chain (initiating trigger → clinical manifestation):

  1. Initiating event: Somatic KRAS and/or GNAS activating mutation arises in appendiceal mucosal epithelium (molecular scale)
  2. Neoplastic transformation: Low-grade appendiceal mucinous neoplasm (LAMN) forms — villiform/undulating/flat low-grade mucinous epithelium with a "pushing" (non-destructive) growth pattern, distending the appendiceal lumen with accumulated mucin (cellular/tissue scale)
  3. Mechanical failure: Progressive luminal distension causes appendiceal wall thinning and perforation (tissue scale) — perforation status is the single most important determinant of subsequent peritoneal dissemination
  4. Peritoneal seeding: Mucin-secreting epithelial cells and acellular mucin extravasate into the peritoneal cavity
  5. Redistribution phenomenon (Sugarbaker, 1994, PMID: 8129480): tumor cells and mucin follow peritoneal fluid circulation dynamics — driven by gravity, the clockwise flow imposed by GI peristalsis, and diaphragmatic/omental fluid reabsorption suction — to accumulate preferentially at fixed anatomic "collection points": the greater omentum ("omental cake"), right hemidiaphragm, Morrison's pouch, and recto-vesical/pelvic pouch (pouch of Douglas), while relatively sparing the peristaltically active small bowel surface (PMC6386305; Sugarbaker 1994, PMC1243111)
  6. Mucin hypersecretion: GNAS mutation-driven Gsα/cAMP signaling upregulates gel-forming mucin production (organism/tissue scale)
  7. Hypoxic amplification loop: As mucin accumulates and tumor nodules enlarge, intratumoral hypoxia develops, and hypoxia-inducible factor HIF-1α binds directly to the MUC2 promoter, further upregulating MUC2 transcription/secretion — a self-amplifying mucin-production loop implicated as a druggable node ("Targeting hypoxia-mediated mucin 2 production as a therapeutic strategy," PMID: 26589109)
  8. Mechanical/compressive end-organ damage: Progressive mucin/tumor accumulation causes fibrosis, adhesions, and compression of abdominal viscera, ultimately impairing bowel, stomach, and other organ function if untreated — the proximate cause of morbidity/mortality
  9. Immunosuppressive microenvironment: CD163+ M2-polarized tumor-associated macrophages (TAMs) are found in 67% of PMP cases (in the microenvironment) and 27% (within tumor cells); in the hypoxic milieu, M2 TAMs promote angiogenesis and exert immunosuppression via PD-L1 expression and Treg recruitment, contributing to disease persistence despite host immune surveillance ("Progress on immuno-microenvironment... in PMP," PMC11271218)

Molecular pathways involved: RAS/MAPK (KRAS), Gsα/cAMP/PKA and downstream A2AR adenosine signaling (GNAS), HIF-1α hypoxia response pathway, TGF-β/SMAD4 (minority of cases), PI3K-AKT (minority).

Mucin biology: MUC2 (gel-forming, intestinal-type secreted mucin) is the dominant molecular marker of PMP and is overexpressed relative to MUC5AC in appendiceal-origin tumors (contrasting with ovarian mucinous tumors, which show a different mucin expression pattern) — MUC2 is described as "a molecular marker for pseudomyxoma peritonei" (PMID: 12218214). MUC5AC and MUC5B are also detected biochemically in patient mucus. CK20, CDX2, and CK7 immunohistochemical staining patterns further support appendiceal (vs. ovarian) origin assignment.

Cell types involved: Mucinous (goblet-cell-like) neoplastic epithelial cells of appendiceal origin (candidate CL term: CL:0000160 goblet cell / intestinal epithelial lineage); CD163+ M2 macrophages (CL:0000891 or CL:0000235 macrophage subtype); regulatory T cells (Tregs, CL:0000815) recruited into the immunosuppressive microenvironment.

Biological processes (candidate GO terms): mucus secretion (GO:0070254), response to hypoxia (GO:0001666), positive regulation of Ras protein signal transduction, adenylate cyclase-activating GPCR signaling (via GNAS/Gsα), cellular response to hypoxia mediated by HIF-1 transcription factor.

Advanced molecular profiling: Whole-exome sequencing has been used to characterize both somatic mutation/LOH landscapes and rare germline variants (see above). Targeted next-generation sequencing panels are used clinically to prognosticate and to identify actionable targets (droplet digital PCR successfully validated druggable mutations in 83% of tumor samples even from low-cellularity intra-abdominal mucin biopsies) (Precision Oncology in PMP, PMC11393541). Patient-derived organoid (PDO) and patient-derived xenograft (PDX) models have enabled genomic characterization revealing KRAS and BRAF as druggable targets.

7. Anatomical Structures Affected

Organ level: - Primary organ: Appendix (vermiform appendix) — site of the originating neoplasm in ~82% of cases with an identifiable primary - Secondary/disseminated involvement: Peritoneum (parietal and visceral), greater omentum, ovaries (secondary seeding, not primary origin in most cases), diaphragmatic surfaces, liver capsule/subcapsular surface (with characteristic "scalloping" from mucin compression rather than true parenchymal invasion), spleen capsule, small and large bowel serosal surfaces (compressed/scalloped rather than typically invaded, per the redistribution phenomenon sparing peristaltically active surfaces) - Body system: Primarily gastrointestinal/peritoneal; secondarily reproductive (ovary) and, via mass effect, respiratory (diaphragmatic compression → dyspnea) and urinary (compression symptoms)

Tissue/cell level: - Peritoneal mesothelial surface and subperitoneal connective tissue (site of mucin deposition and fibrotic reaction) - Mucinous epithelial cell strips/glands floating within extracellular mucin pools (the defining histologic picture) - Omental adipose/connective tissue, remodeled into the characteristic "omental cake"

Subcellular level: Not a classically subcellular-organelle disease; relevant compartments include the secretory pathway (ER/Golgi) of mucin-producing goblet-like cells and the nuclear compartment for GNAS/KRAS/TP53 signaling effects.

Localization/UBERON candidates: UBERON:0004063 (appendix), UBERON:0002358 (peritoneum), UBERON:0002101 (omentum), UBERON:0000992 (ovary), UBERON:0002107 (liver — capsule), UBERON:0002106 (spleen — capsule).

Lateralization: Not applicable in the classic sense; disease distribution is dictated by peritoneal fluid dynamics (redistribution phenomenon) rather than left/right asymmetry, though there is a described right-hemidiaphragm predilection over the left, attributed to differential fluid reabsorption dynamics.

8. Temporal Development

Onset: Adult-onset, most commonly diagnosed in the 5th–6th decade of life; the underlying LAMN may be present and slowly enlarging for years to a decade or more prior to perforation and clinical presentation. Onset pattern is typically insidious, with a substantial fraction discovered incidentally at unrelated surgery or imaging.

Progression/staging: - AJCC 9th edition staging for appendiceal adenocarcinoma/PMP now formally distinguishes: - M1a — intraperitoneal acellular mucin only, no identifiable tumor cells in disseminated mucinous deposits - M1b — intraperitoneal metastasis with tumor cells present in peritoneal mucinous deposits - M1c — extraperitoneal metastasis - T4 — tumor (including acellular mucin) involving the serosal (visceral peritoneal) surface or directly invading adjacent organs - Stage grouping: M1a disease (regardless of grade) is Stage IVA; M1b disease is staged IVA (Grade 1) or IVB (Grade 2/3/X) depending on histologic grade - Histopathologic grading (the dominant prognostic staging framework in practice) — see Section 10/Diagnostics - Progression rate: Highly variable by grade — low-grade (DPAM) disease can be indolent over years to decades; high-grade (PMCA), and especially high-grade with signet-ring cells (PMCA-S), progresses more rapidly and carries substantially worse prognosis - Disease course pattern: Generally progressive if untreated, though the indolent low-grade form can appear relatively "stable" over long intervals; recurrence after CRS-HIPEC affects roughly one-quarter to nearly half of treated patients

Remission patterns: Primarily treatment-induced (via complete cytoreductive surgery ± HIPEC); spontaneous remission is not described. Long-term survivors after complete cytoreduction can achieve what is sometimes termed "clinical cure," though recurrence surveillance is typically lifelong given the biology of residual microscopic disease.

Critical periods/intervention windows: The window before appendiceal perforation (i.e., diagnosis and resection of an intact LAMN) represents the key preventive opportunity; once peritoneal dissemination has occurred, the critical determinant of outcome becomes achieving complete cytoreduction (CC-0/CC-1) at the time of definitive surgery — later-stage disease with higher PCI is progressively less amenable to complete resection.

9. Inheritance and Population

Epidemiology: - Incidence: Classically cited at 1–2 cases per million per year; a more recent statistical estimate calculated an incidence of 3.2 per million per year, with an estimated prevalence around 22 per million (Estimating the Prevalence of PMP in Europe, PMC7752784) - China nationwide data: Urban Chinese cohort study found crude PMP prevalence of 2.47 per million person-years in 2016, with higher prevalence in females than males (PMID: 35764460) - Orphanet prevalence class: Consistent with "1-9 per 1,000,000" (ultra-rare) band - Appendiceal mucinous neoplasm base rate: A mucinous epithelial neoplasm is identified in ~0.3% of all appendiceal specimens, and ~20% of these patients go on to develop PMP

Inheritance pattern: PMP is overwhelmingly sporadic, driven by somatic (not germline) mutation. No established Mendelian inheritance pattern exists. The rare familial clusters reported (father-daughter; first-degree relative pairs; twin brothers; a sibling pair) suggest an as-yet-uncharacterized predisposition in isolated kindreds, but no confirmed inheritance mode (AD/AR/X-linked) has been established — these remain case-report-level observations rather than a validated genetic syndrome.

Penetrance/expressivity/anticipation/mosaicism/founder effects/consanguinity/carrier frequency: Not applicable/not established, given the sporadic somatic-driver nature of the disease and the rarity of any hereditary predisposition signal.

Population demographics: - Sex ratio: Notable female predominance is repeatedly reported (partly an artifact of secondary ovarian involvement drawing gynecologic-oncology attention, but a true excess in some population cohorts as well, e.g., the Chinese nationwide cohort) - Age distribution: Peak diagnosis in the 50s; can occur across a wide adult age range - Geographic distribution: No striking endemic geographic clustering has been described; incidence estimates have been generated primarily from European and Chinese cohorts, likely reflecting availability of centralized referral/registry data from specialist CRS-HIPEC centers rather than a true geographic risk gradient - Ethnic/racial predisposition: No specific ethnic predisposition established in the literature reviewed

10. Diagnostics

Laboratory tests/biomarkers: - CEA, CA19-9, CA-125 — the three standard serum tumor markers monitored; elevated preoperatively in 75%, 58%, and a majority of patients respectively; used for diagnosis, disease-burden estimation, treatment response monitoring, and prognosis (PMID: 34733775; PMID: 27038681) - CA72-4, CA242 — additional markers studied in serum and ascites for prognostic stratification - Number of elevated markers correlates with PCI and resectability

Imaging: - Contrast-enhanced CT of chest/abdomen/pelvis is the imaging modality of choice; characteristic finding is "scalloping" of the liver/spleen surface from loculated mucin deposits, plus omental caking and ascites with a gelatinous (rather than simple fluid) density - MRI — superior soft-tissue contrast; CT alone consistently underestimates peritoneal spread; combined CT+MRI improves preoperative PCI estimation accuracy compared to CT alone - Peritoneal Cancer Index (PCI) (Sugarbaker scoring system, 0–39) is the standard quantitative surgical/radiologic staging tool for disease extent; PCI ≥20 is generally considered a marker of unresectability - Diagnostic laparoscopy is sometimes used when CT findings are equivocal

Histopathology (definitive diagnosis) — PSOGI 2016 consensus classification (Peritoneal Surface Oncology Group International modified Delphi process, PMID: 26492181): 1. Acellular mucin (AC) — mucin without identifiable neoplastic epithelium 2. Low-grade mucinous carcinoma peritonei (LG-MCP) = synonym DPAM (disseminated peritoneal adenomucinosis) — abundant extracellular mucin, scant epithelial strips/small islands, minimal cytologic atypia, maintained cell polarity, low mitotic activity 3. High-grade mucinous carcinoma peritonei (HG-MCP) = synonym PMCA (peritoneal mucinous carcinomatosis) — enlarged vesicular nuclei, full-thickness stratification, loss of polarity, prominent nucleoli, cribriform/micropapillary architecture, increased mitoses 4. High-grade mucinous carcinoma peritonei with signet ring cells (HG-MCP-S) = PMCA-S — >50% signet-ring morphology; worst prognosis of the four tiers

This PSOGI system superseded the original Ronnett et al. 1995 three-tier system (DPAM / PMCA / intermediate PMCA-I/D, PMID: 7503361) and subsequent iterations (Bradley 2006 two-tier; Shetty 2013 three-tier PMP1-3), consolidating terminology while retaining DPAM/PMCA as accepted synonyms.

Immunohistochemistry: MUC2 (positive marker), CK20, CDX2 (support appendiceal/intestinal origin) vs. CK7 (favors non-appendiceal/ovarian primary); EpCAM also studied.

Genetic/molecular testing: Targeted NGS panels (KRAS, GNAS, TP53, SMAD4, BRAF, PIK3CA) increasingly used for prognostication and precision-therapy matching; droplet digital PCR (ddPCR) has been validated as feasible even on low-cellularity intra-abdominal mucin biopsies (83% mutation detection rate), addressing the classic challenge of low tumor cellularity in PMP specimens for standard sequencing.

Differential diagnosis: Peritoneal mesothelioma (can closely mimic PMP radiologically and clinically — asbestos/smoking-associated, unlike PMP), primary ovarian mucinous carcinoma, peritoneal carcinomatosis from other GI/pancreatic primaries, simple/loculated ascites.

Staging: AJCC 9th edition TNM system for appendiceal neoplasms (T4/M1a/M1b/M1c as above) plus the surgical/pathologic PCI and completeness-of-cytoreduction (CC) score are the operative staging tools that drive management decisions.

Screening: No population screening program exists given the extreme rarity of PMP; incidental appendiceal mucinous neoplasms are occasionally detected on imaging/colonoscopy performed for unrelated indications, and prompt resection before perforation is the closest analog to secondary prevention.

11. Outcome/Prognosis

Survival by histologic grade (the dominant prognostic determinant): - Ronnett et al. (1995) original series: 5-year survival 84% for DPAM vs. 6.7% for PMCA (PMID: 7503361) - Contemporary CRS-HIPEC-treated series: 5-year OS approximately 81% (DPAM) / 78% (hybrid) / 59% (PMCA) in one series, and 93% (acellular mucin) / 69.8% (DPAM) / 55% (PMCA) in another - Single-surgeon uniformly treated cohort: 5-year survival 75% (DPAM), 50% (PMCA-I/D), 14% (PMCA) - PMCA-S (signet-ring) subtype consistently shows the worst prognosis of the four PSOGI tiers - With modern CRS-HIPEC, large series report OS up to 196 months, with 5- and 10-year survival rates reaching 74% and 63%, and some large series report median survival of 16.3 years and 86% 5-year OS in favorable subsets

Prognostic factors (independent predictors of survival): - Completeness of cytoreduction (CC-0/CC-1 vs. CC-2/CC-3) — consistently the single strongest prognostic factor across studies, generally outweighing even histologic grade or mutation status - Histologic grade/PSOGI subtype — independent predictor - Molecular status — GNAS and/or KRAS mutation independently associated with worse survival in the 223-case cohort (combined HR 1.87, p=0.004); TP53 mutation associated with worse survival and higher grade - PCI at presentation — higher PCI associated with lower rates of achievable complete cytoreduction and worse outcomes - Elevated tumor markers (CEA, CA19-9, CA-125) — associated with higher disease burden and worse prognosis - Postoperative anemia within 24h — recently reported as an independent prognostic factor in one series

Morbidity/complications: Bowel obstruction, malnutrition, adhesion-related complications, and the substantial perioperative morbidity of CRS-HIPEC itself (a long, complex operation) are the principal sources of disease- and treatment-related morbidity. Recurrence occurs in roughly one-quarter to nearly half of CRS-HIPEC-treated patients.

Quality of life/functional outcomes: Limited PMP-specific structured QOL data; the disease and its treatment both carry significant impact on daily functioning, though many long-term survivors after complete cytoreduction report favorable long-term function relative to the pre-treatment natural history of progressive obstruction.

12. Treatment

Standard of care — Cytoreductive Surgery + Hyperthermic Intraperitoneal Chemotherapy (CRS-HIPEC): - CRS involves radical peritonectomy and multivisceral resection to remove all visible tumor and mucin, followed by intraoperative HIPEC to treat microscopic residual disease - This is now the internationally accepted standard treatment, significantly prolonging survival and, in a subset, achieving durable long-term survival/clinical cure - Completeness of cytoreduction (CC score) is the key modifiable surgical determinant of outcome (NCIT candidate: NCIT:C15329 Surgical Procedure; more specifically a cytoreductive/peritonectomy procedure) - HIPEC agents: Mitomycin C (traditional standard) and oxaliplatin are the most-studied intraperitoneal agents; a 10-year outcome analysis of a randomized trial compared mitomycin C vs. oxaliplatin HIPEC for appendiceal neoplasms with peritoneal dissemination. A newer retrospective propensity-matched study found cisplatin + docetaxel HIPEC superior to cisplatin + mitomycin C for PMP survival, suggesting a role for personalized HIPEC regimen selection - NCIT candidate terms: NCIT:C15632 (Chemotherapy); therapeutic_agent CHEBI terms for mitomycin C, oxaliplatin, cisplatin, docetaxel, fluorouracil

Systemic chemotherapy (for unresectable/recurrent disease): - FOLFOX (oxaliplatin/5-FU/leucovorin) used as first-line systemic therapy for unresectable mucinous appendiceal adenocarcinoma with PMP, with promising results in several series - Mitomycin C + capecitabine — Phase II study showed clinical benefit in 38% of 39 assessable patients; 2 patients converted from unresectable to resectable - NCT01946854 — randomized crossover trial of systemic chemotherapy for metastatic well-differentiated mucinous appendiceal adenocarcinoma with PMP (MD Anderson) - NCT00352755 — Phase II peritonectomy + intraperitoneal 5-FU + systemic oxaliplatin/5-FU/leucovorin (terminated)

Targeted/precision therapy (emerging): - BRAF V600E-mutant, high-grade PMP: Encorafenib (BRAF inhibitor) showed significant monotherapy efficacy in BRAF V600E patient-derived organoid/xenograft models - KRAS G12D: The KRAS G12D-selective inhibitor MRTX1133 showed dose-dependent efficacy in preclinical PMP models - Standard chemotherapy (mitomycin C, oxaliplatin) showed only minimal effect in these same preclinical models, reinforcing rationale for a precision-oncology approach guided by ddPCR/NGS mutation profiling (Precision Oncology in PMP, PMC11393541) - Anti-EGFR agents (cetuximab) have shown only limited benefit despite high KRAS mutation prevalence - Immune checkpoint blockade (anti-PD-1/PD-L1) is of theoretical interest given the CD163+ M2-macrophage/PD-L1-rich immunosuppressive microenvironment, but clinical data specific to PMP remain preliminary

Palliative/emerging local therapy: - PIPAC (Pressurized IntraPeritoneal Aerosol Chemotherapy) — minimally invasive, low-dose aerosolized intraperitoneal chemotherapy (typically cisplatin 7.5 mg/m² + doxorubicin 1.5 mg/m²) for unresectable/recurrent disease; a case report documented clinical and histological remission in a PMP patient (PMID: 26076000); overall PIPAC across peritoneal malignancies carries a severe complication rate of ~6.2%, with improved survival in patients receiving multiple sessions or bidirectional (systemic + intraperitoneal) treatment

Supportive care: Nutritional support, management of bowel obstruction, and symptom-directed palliation (ascites/mucin drainage) for advanced/recurrent disease not amenable to further cytoreduction.

Treatment algorithm: Complete surgical cytoreduction (CC-0/CC-1) + HIPEC is preferred whenever feasible based on PCI/resectability assessment; unresectable disease is managed with systemic chemotherapy ± PIPAC, with molecular profiling increasingly used to select targeted agents (BRAF/KRAS inhibitors) in appropriate mutation-positive patients.

13. Prevention

Primary prevention: No general population-level primary prevention exists given the sporadic, non-environmentally-triggered etiology. The only actionable primary-prevention-adjacent measure is timely diagnosis and resection of an appendiceal mucinous neoplasm (LAMN) before perforation occurs, since perforation is the proximate mechanical trigger for peritoneal dissemination.

Secondary prevention: No population screening program exists (extreme rarity precludes cost-effective screening). Incidental detection of appendiceal mucinous lesions on imaging or at appendectomy for unrelated indications, followed by prompt appropriate surgical management, functions as de facto secondary prevention.

Tertiary prevention: Complete cytoreductive surgery with HIPEC is itself the principal tertiary-prevention strategy — preventing progression/recurrence in patients who already have established peritoneal disease. Surveillance imaging and tumor marker monitoring after CRS-HIPEC are used to detect recurrence early, when repeat cytoreduction may still be feasible.

Genetic counseling: Not routinely indicated given the sporadic somatic nature of disease; counseling could be considered on a case-by-case, research basis for the rare identified familial kindreds, but no validated predictive genetic test or established hereditary syndrome exists to counsel around.

Public health/environmental interventions: Not applicable — no known modifiable environmental risk factor.

14. Other Species / Natural Disease

Naturally occurring veterinary disease: PMP-like syndromes have been documented in dogs as a rare complication of caecal/appendiceal (cecal, since dogs lack a true vermiform appendix analog but a functionally similar cecal apex process is described) mucocele/mucinous neoplasm perforation. Malignant mucocele cases in dogs show neoplastic cells penetrating the wall and seeding the peritoneum with adhesive, semi-solid mucin containing neoplastic cells — mirroring the human mechanism closely (McKenna et al., caecal mucocele in a dog, JSAP).

Canine myxoid mesothelioma has also been reported with a clinical presentation resembling pseudomyxoma peritonei (gelatinous, translucent peritoneal material), though this represents a mesothelial rather than epithelial-mucinous-neoplasm mechanism and should be distinguished from true PMP.

Taxonomy: No formal OMIA entry specific to canine PMP was identified; these remain individual case reports rather than a curated naturally-occurring-disease model in veterinary genetics databases.

Comparative biology: The core redistribution-phenomenon mechanism (fluid-dynamics-driven mucin/tumor cell distribution to fixed anatomic collection points) is conserved enough between human and canine disease that the veterinary cases are cited in the human clinical literature as supportive natural-history evidence, though systematic comparative pathology/genomic characterization (KRAS/GNAS mutation status in canine cases) has not been reported in the sources reviewed.

Zoonotic potential: None — not a transmissible disease in either species.

15. Model Organisms

Patient-derived xenograft (PDX) models: - PDX models generated by serial engraftment of patient PMP tumors into immunocompromised mice have been established and reported in both mice and rats - Notably, high-grade PMP tumors have been successfully xenografted, but low-grade tumors have not — a significant modeling limitation given that most clinically relevant PMP is low-grade - Kuracha et al. (2016) demonstrated that PDX models of PMP recapitulate the human inflammatory tumor microenvironment (PMID: 26833741; PMC4831290), supporting their use for microenvironment-directed drug studies - Orthotopic mouse models specifically reproducing the PMCA-I (intermediate) histopathologic subtype have also been described (American Journal of Pathology, "Orthotopic Animal Model of Pseudomyxoma Peritonei") - Genomic characterization of PDX/organoid collections revealed KRAS and BRAF as druggable targets, with BRAF^V600E^ models responding to targeted therapy in vivo (encorafenib) — direct translational validation from model to precision therapy hypothesis

Patient-derived organoid (PDO) models: - A 2024 "combinatorial culture strategy" was developed specifically to overcome the low tumor cellularity/high mucin content that has historically made PMP difficult to culture as organoids (Varinelli et al., Journal of Surgical Oncology 2024; PMC11826015) - PDO models are positioned as a platform for multilevel preclinical drug testing, biomarker discovery, and identification of novel therapeutic targets - Combined PDO/PDX collections have enabled the KRAS-G12D-inhibitor (MRTX1133) and BRAF-inhibitor (encorafenib) preclinical efficacy studies cited above

Model limitations: The inability to reliably xenograft low-grade disease (the more common and more indolent clinical phenotype) is the single most significant acknowledged gap in current PMP modeling — most existing PDX/PDO data are biased toward the more aggressive high-grade biology, limiting translational inference for the majority of low-grade PMP patients. No genetically engineered (germline knock-in/knockout) mouse model specifically recapitulating spontaneous appendiceal-origin PMP was identified in the sources reviewed; existing models are xenograft/organoid-based rather than genetically engineered.

Research applications: These models have been used to (1) confirm the human inflammatory/immunosuppressive tumor microenvironment is recapitulated in vivo, (2) validate KRAS/GNAS/BRAF as druggable molecular targets, (3) test BRAF and KRAS-G12D inhibitors with in vivo efficacy readouts, and (4) demonstrate that standard cytotoxic chemotherapy (mitomycin C, oxaliplatin) has limited direct antitumor effect in these models — supporting the rationale that HIPEC's clinical benefit may derive substantially from mechanical/cytoreductive and locoregional pharmacokinetic effects rather than purely from cytotoxic potency against the tumor cell population itself.

Summary of Key Ontology Term Suggestions

Category Suggested terms
Disease MONDO:0017048; ORPHA:26790
Genes hgnc:6407 (KRAS), hgnc:4392 (GNAS), hgnc:11998 (TP53), hgnc:6770 (SMAD4), hgnc:1097 (BRAF), hgnc:8975 (PIK3CA)
Phenotypes (HP) HP:0003270 (Abdominal distention), HP:0002027 (Abdominal pain), HP:0025144 (Bowel obstruction), HP:0000023 (Inguinal hernia), HP:0100615 (Ovarian neoplasm), HP:0002094 (Dyspnea)
Anatomy (UBERON) UBERON:0004063 (appendix), UBERON:0002358 (peritoneum), UBERON:0002101 (omentum), UBERON:0000992 (ovary)
Biological process (GO) GO:0070254 (mucus secretion), GO:0001666 (response to hypoxia)
Cell types (CL) goblet/mucinous epithelial cell; CD163+ M2 macrophage; regulatory T cell (CL:0000815)
Chemicals (CHEBI) mitomycin C, oxaliplatin, cisplatin, docetaxel, fluorouracil
Treatment (NCIT) NCIT:C15329 (Surgical Procedure — cytoreductive surgery), NCIT:C15632 (Chemotherapy — HIPEC)

Sources

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Unverifiable 0
Quoted claims checked 2
Quoted claims found in source 1
Quoted claims not found in source 1
References weighed for topical relevance 31
On topic 19
Off topic 0

Unresolved references

These identifiers did not resolve to a record and may be fabricated. A lookup that failed for transport reasons is indistinguishable from one that failed because the record does not exist, so spot-check before acting on them:

  • DOI:10.3390/biomedicines11072049](https://doi.org/10.3390/biomedicines11072049 (1 mention) - Identifier did not resolve to a record

Quotes not found in the cited source

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

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

  • PMID:12218214 (abstract only): "a molecular marker for pseudomyxoma peritonei"
  • closest text in source: "MUC2 is therefore a reliable molecular marker for pseudomyxoma peritonei."