Villous tumor of the colon and rectum with special reference to roles of p53 and bcl-2 in adenoma-carcinoma sequence

Villous tumors are rare and their histological diagnosis from biopsy specim ens is often difficult. To ascertain its tumor progression, including the g enetic events, would be useful for clinical treatment. Clinicopathological features and the expression of p53 and bcl-2 proteins were investigated in 50 villous tumors from 49 patients, The patients' ages ranged widely from 3 2 to 84 years (average, 61 years). Females were more frequently affected th an males (male : female ratio, 20 : 29). Thirty-six (72%) of the villous tu mors were present within the sigmoid colon and rectum, Histologically 17 (3 4%) of these contained carcinomas in villous adenomas (CIVA), while 24 (73% ) of 33 villous adenomas (VA) contained high-grade dysplasia. Most of the C IVA revealed well-differentiated adenocarcinoma, often with focal or diffus e mucin pools, Three lesions of invasive carcinomas were composed of extrem ely well-differentiated components, The average size of the CIVA (79 mm) wa s significantly larger than that of the VA (51 mm). Overexpression of p53 p rotein was recognized in 12% of VA, in 24% of mucosal components of CIVA an d in 18% of invasive components of CIVA. Overexpression of bcl-2 was recogn ized in 57% of VA, 33% of mucosal components of CIVA, and 7% of invasive co mponents of CIVA. Several characteristic features were recognized in villou s tumors, which comprised: (i) a high frequency of coexistence of carcinoma ; (ii) multiple foci of carcinomas arising in adenomatous tumors; (iii) a l ower histological grade of carcinomas, often with mucin pools; (iv) the exi stence of extremely well-differentiated adenocarcinomas; and (v) less frequ ent expression of p53 protein in the carcinomatous components, According to these findings, the pathway of tumor progression in the villous tumors is possibly different from that of sporadic colorectal carcinomas. Because of the peculiarity of villous tumors, careful clinical management is required.