Pseudomyxoma peritonei
A rare disease that fills the abdomen with mucus and which, operated on in time and in the right place, has the best long-term results in all of peritoneal surgery.
Pseudomyxoma peritonei almost always starts somewhere small: the appendix. A mucinous tumour of the appendiceal wall ruptures it, and the cells that escape implant across the peritoneum and carry on doing the only thing they know how to do, which is produce mucus.
That mucus builds up. It does not invade organs the way another cancer would, but it wraps around them, displaces them and eventually takes up room. Hence the name it goes by in English, jelly belly, and hence the commonest symptom being an abdomen that grows with no explanation.
It is a rare disease, and that rarity is part of the problem: many patients pass through more than one hospital before anyone names it properly. It is also the disease in which cytoreductive surgery with intraperitoneal chemotherapy gives its best results, by a distance.
There are three typical routes, and none of them looks like what people expect of a cancer.
Low-grade pseudomyxoma grows slowly and virtually never metastasises through the bloodstream: it does not go to the liver or the lung. It stays in the abdominal cavity.
That has an enormous practical consequence: if all the disease is inside a cavity that can be reached, removing it in full can be attempted. Which is why here the sheer volume of disease does not, on its own, rule surgery out.
In most tumours there is a ceiling of extent above which surgery is not offered. In low-grade pseudomyxoma there is no absolute PCI limit: what decides is whether the abdomen can be left free of visible disease. A PCI of 30 from mucinous disease that spares the mobile bowel may be entirely resectable.
PCI thresholds by histology as set out in the author's material, drawing on the international consensus documents (PSOGI and the Chicago Consensus).
In the founding series of 385 patients, with complete cytoreduction and low-grade histology — disseminated peritoneal adenomucinosis — five-year survival was 86%. In the intermediate variant, 50%. Where cytoreduction was incomplete, 20% at five years and 0% at ten.
The longer-term data come from a pooled analysis of 2,298 patients treated at sixteen centres: median survival of 196 months, that is over sixteen years, with 63% of patients alive at ten years and 59% at fifteen.
Read it with an eye on the first figure of each pair: the difference between 86% and 20% is not in the disease. It is in whether the cytoreduction was completed.
Sugarbaker PH, Chang D. Annals of Surgical Oncology, 1999 (385 patients). Pooled analysis of 2,298 patients across 16 centres, as recorded in the author's monograph. In that same analysis, incomplete cytoreduction, major postoperative complications, aggressive histology and prior systemic chemotherapy were independent predictors of worse survival.
In that analysis of 2,298 patients, having received systemic chemotherapy before surgery was an independent predictor of worse survival.
It does not mean chemotherapy causes harm in itself; it means that in this disease it is not the first step, and that starting there can delay the one intervention that changes the course. If you have been diagnosed with pseudomyxoma and the plan you are offered begins with chemotherapy, it is reasonable to ask for a peritoneal surgery unit to see the case first.
Pooled analysis of 2,298 patients with PMP treated with CRS+HIPEC across 16 centres.
What prevents surgery is almost never how much mucus there is. It is where it sits and what it encases.
International consensus on appendiceal neoplasms (2025), recorded in the author's monograph with level A evidence and a strong recommendation.
This is the peritoneal disease in which the team's experience shows most, because the surgery is long, the dissection is tedious and the result depends on completing it. A centre that sees two cases a year does not build the judgement of one that sees them monthly.
In Spain, peritoneal malignancy care is organised through designated reference centres. Hospital General Universitario Gregorio Marañón is a CSUR centre for peritoneal carcinomatosis.
If you have been told your disease cannot be operated on, in pseudomyxoma that sentence deserves a second reading more than in any other: the criteria that rule it out here are not those of an adenocarcinoma.
The figures above describe groups of patients operated on in experienced centres, not any one person. Your case depends on the exact histology, on the distribution of disease and on your general condition.
This does not replace a consultation, and it is not a diagnosis. If you have a report with the word pseudomyxoma on it, what you need is a team that treats this disease routinely.
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