Villous adenocarcinoma of the colon and rectum: a clinicopathologic study of 36 cases.

Some colorectal adenocarcinomas show villous architecture with morphologic similarities to tubulovillous or villous adenomas. We reviewed 420 consecutive colorectal adenocarcinoma resection specimens and found that 95 tumors (23%) showed areas of villous architecture. Thirty-six tumors (8.6%) in 35 patients showed more than 50% villous architecture and were designated villous adenocarcinomas. Only 42% of the villous adenocarcinomas showed severe atypia and only 44% of the available pre-resection biopsies of these tumors were diagnosed as adenocarcinoma. Epithelial islands in desmoplastic stroma (EIDS) may be helpful in the diagnosis of these tumors. EIDS were found in 97% of the resection specimens for villous adenocarcinomas and none of 62 resection specimens for tubulovillous or villous adenomas. The presence of EIDS showed a 67% sensitivity, 100% specificity, and 100% predictive value in the diagnosis of villous adenocarcinoma in a blinded review of villous tumors. On review of the pre-resection biopsies of villous adenocarcinoma without a final diagnosis of adenocarcinoma, 40% showed EIDS. Clinical follow-up of the 35 patients with villous adenocarcinoma showed that only one died of colorectal adenocarcinoma (median follow-up, 46 months). This sole patient dying of colorectal adenocarcinoma showed a synchronous advanced stage of nonvillous adenocarcinoma at the time of diagnosis. Villous adenocarcinoma is a diagnostically challenging subset of colorectal adenocarcinoma, which appears to be associated with a favorable prognosis. Classifying these tumors as a special type of colorectal cancer may facilitate the development of diagnostic adjuncts and optimal treatment protocols.