Colorectal carcinoma associated with serrated adenoma - prevalence, histological features, and prognosis

Serrated adenoma has been proposed to be a distinct entity among colorectal neoplasms. Progression to frank carcinoma has been suggested in individual cases, but the prevalence of carcinomas originating from serrated adenomas and their clinico-pathological characteristics are not known. In the prese nt study a large series of colorectal cancers was analysed for the occurren ce of serrated adenoma In association with carcinoma and clinico-pathologic al features were compared in cases with and without serrated adenoma, Speci mens from 466 colorectal carcinoma patients undergoing operations between 1 986 and 1996 were re-evaluated for the presence of juxtaposed serrated aden oma and carcinoma. Clinico-pathological features such as location, Dukes' s tage, histological grade, mucinous differentiation, and prognosis were eval uated. Twenty-seven carcinomas (5.8%) were Pound in association with an adj acent serrated adenoma, Eight of the patients were male and 19 were female. All of these adenocarcinomas showed a serrated appearance resembling that of serrated adenomas, Nine (33%) cases were mucinous and a mucinous compone nt,ras present in 11 (41%) additional cases, The majority of the tumours we re located either in the caccum (14 cases; 51%) or in the rectum (9 cases; 33%), DNA microsatellite instability was more common in carcinomas associat ed with serrated adenoma (37.5%) than in other carcinomas (11.0%). It is co ncluded that carcinoma associated with serrated adenoma is a distinct type of colorectal neoplasm, accounting for 5.8% of all colorectal carcinoma cas es in this study. Predilection for the caecum and the rectum may reflect th eir aetiological factors. Female preponderance is contrary to that reported for hyperplastic polyps and serrated adenomas, Copyright (C) 2000 John Wil ey & Sons, Ltd.