Villous adenoma of the colon.

Abstract

k 53-year-old man presented abler 4 nionths of abdoniinal pain and diarrhea. An upper gastrointestinal and small-bnvcl series revealed a cecal tilling defect with poorly defined margins and changing shape (Fig. IA). CT showed a softtissue mass in the cecum with ileocecal intussusception ( Fig. I B ). Abler colonoscopy. a right hemicolectomy was performed for a 6cm polypoid. sessile. villous tumor adjacent to the ileocecal valve. The final pathologic diagnosis was villous adenoma. without evidence ol nialignancy ( Fig. I C). Villous adenomas are benign tuniors consisting of n ultiple frondlike structures that project into the lumen froiii the base of the niucosa I I J. Most are located in the rectosignioid region. hut they may occur throughout the colon. Although villous adenomas are usually sessile. they may be pedunculated. Larger than the typical adenomatous polyp. about 75C4 of villous adenomas exceed 2 cm in diameter at presentation. Vi llotis adenomas are often asyniptomatic. hut when large amounts of mucus are secreted into the lumen, the result is diarrhea. Uncontrolled diarrhea may lead to fluid. protein. and electrolyte (especially pota.ssium) depletion. and extremely large tumors ( l()-15 cm) may produce obstructive symptoms. Rectal bleeding is unusual because the mucosal surface usually remains intact. On barium examinations, villous adenomas usually show reticular or granular mucosal patterns and feathery margins 121. Postevacuation views are often helpful in showing bariuiii within the interstices of bulky villous tumors. Villous adenomas have a soft consistency. and their appearance may change on serial films or with palpation. The appearance 011 CT is less specific. Although villous adenomas represent only l0C/ of all benign polyps, they have disproportionate clinical significance because of their high potential for malignant change (31. Vilbus adenoinas may progress to invasive carcinomas. and infiltrating carcinoma niay be found in nearly 40% of specimens on careful sectioning. Invasive carcinomas are usually found at the base of the lesion. Large size and ulceration have been suggested as radiographic signs of malignancy [4]. Biopsies at colonoscopy may be misleading because of inadequate tissue sampling: therefore, complete excision is indicated in all cases of villous adenoma.