Inflammatory "Cap" Polyposis: A Case Report of a Rare Nonneoplastic Colonic Polyposis

Inflammatory cap polyposis (ICP) is a rare nonneoplastic polyposis of the colon of unknown etiology that can be confused with prolapse-induced polyps and hyperplastic polyposis. We contribute a case of ICP from a 59-year-old woman who was affected by severe constipation and hematochezia. Numerous sessile and semipedunculated polyps were found in the colon, all with cap of whitish fibrin. Histology revealed erosion of the surface, superficial dilated crypts filled with mucoid inflammatory exudate, and minimal crypt serration, all findings typical of ICP. Only the largest polyps had smooth muscle in the mucosa. Ki-67 showed modest expansion and irregular distribution of the crypts proliferative areas. Low-degree positivity for p16, similar to that of hyperplastic polyps, was found. CK20 was expressed as in normal mucosa. Distinguishing between ICP and other polyposis is important because of difference in management.