Pseudomyxoma Peritonei, from the CureRays guide library.

Pseudomyxoma peritonei is a rare condition in which a usually slow-growing tumor — most often from the appendix — fills the belly with jelly-like mucus, and it is best treated with extensive surgery to remove the deposits combined with heated chemotherapy washed through the abdomen.

What it is.

Pseudomyxoma peritonei (PMP) is an uncommon condition in which mucus-producing tumor cells spread across the lining of the abdomen (the peritoneum) and slowly fill the belly with thick, jelly-like mucus — sometimes called 'jelly belly.' It usually begins as a small tumor of the appendix that bursts and seeds the abdominal cavity, although it can occasionally arise from the ovary or bowel. Most forms grow slowly and rarely spread through the bloodstream to distant organs; instead, the problem is that the mucus and tumor build up inside the abdomen, pressing on organs over time. Because of this distinctive behavior, the most effective treatment is a specialized operation to remove all visible disease, combined with heated chemotherapy delivered directly into the abdomen, done at experienced centers.

How radiation treats it.

Radiation damages the DNA inside tumor cells so they cannot keep growing. Pseudomyxoma peritonei is unusual in that radiation is rarely used: the disease coats the surfaces inside the abdomen rather than forming a single mass, and the bowel and other organs cannot safely tolerate the wide radiation field that would be needed. Instead, the 'local therapy' is delivered surgically and through heated chemotherapy washed directly through the abdomen. Radiation is reserved for occasional symptom relief — for example, a single painful or obstructing spot — where a focused, painless course of treatment can help.

The ways we can treat it.

Surgery + intraperitoneal chemotherapy (primary). The core treatment is local, not radiation: clearing all visible disease and bathing the abdomen in heated chemotherapy to reach microscopic cells across the peritoneal surface.

Palliative external-beam radiation (rare). In uncommon situations, focused radiation can ease a specific painful or obstructing deposit; radiation is not a routine part of treatment for this abdominal-surface disease.

Questions we hear often.

Is pseudomyxoma peritonei a cancer? It is a borderline or low-grade cancerous condition in most cases. Even the slow-growing form behaves like cancer in that it spreads across the abdomen and can be life-threatening if left untreated, but it usually grows slowly and rarely spreads to distant organs through the bloodstream.

Why is radiation not the main treatment? The disease coats the lining and surfaces throughout the abdomen rather than forming one mass, and the bowel cannot safely receive radiation over such a wide area. The most effective local treatment is surgery to remove all visible disease combined with heated chemotherapy delivered directly into the abdomen.

Can it come back, and can it be treated again? Yes. Because it tends to stay within the abdomen, mucus can slowly rebuild, and many patients can have repeat surgery if needed. Long-term follow-up at an experienced center helps catch and manage any return early.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.