Pedunculated peritoneal surface polyps in pseudomyxoma peritonei syndrome.

AIMS Pseudomyxoma peritonei syndrome is a rare disease that originates from an adenomatous lesion of the appendix that, from pressure, perforates to gain access to the free peritoneal cavity. The relative sparing of the small bowel surfaces allows for complete cytoreduction even though many kilograms of mucinous tumour exist at other sites within the abdomen and pelvis. The purpose of this study was to examine the mechanism whereby the small bowel remains free of gross tumour and peritoneal surface polyps form. METHODS AND RESULTS Peritoneal surface polyps were harvested and examined grossly and histologically. A hypothesis for their formation on small bowel and small bowel mesentery was proposed. Polyps are known to be associated with repeated motion of enteric contents moving past adenomatous tissue so that, over time, an elongated stalk is created. We have repeatedly observed pedunculated polyps on the peritoneal surface of the small bowel in patients with pseudomyxoma peritonei syndrome. No other site within the peritoneal cavity has had a pseudomyxoma polyp located upon its surface. CONCLUSIONS The peristaltic motion of the small bowel causes adherent adenomatous tissue to develop a stalk on the peritoneal surface. Motion not only creates polypoid lesions but also repeatedly clears mucinous tumour cells from the small bowel surface. With pseudomyxoma peritonei and with other types of cancerous dissemination, prevention of adherence by motion may interfere with the implantation of malignant cells.