MICROSATELLITE INSTABILITY IN SPORADIC MUCINOUS COLORECTAL CARCINOMAS- RELATIONSHIP TO CLINICOPATHOLOGICAL VARIABLES

A series of 44 sporadic mucinous colorectal carcinomas was analysed fo r microsatellite instability; 30 consecutive sporadic non-mucinous col orectal cancers served as controls, Mucinous carcinomas showed microsa tellite instability more frequently than non-mucinous cancers: 26/44 a nd 8/30, respectively (P=0.005); the difference was higher for cancers with two or more microsatellite alterations: 12 of the 44 mucinous ca rcinomas versus one of the 30 non-mutinous carcinomas (P=0.007). On co mparing the clinico-pathological features of mucinous carcinomas with and without microsatellite instabilities, no differences were found,vi th respect to the following variables: sex ratio, tumour localization, tumour size, peritumoural lymphocytic infiltration, Crohn's-like lymp hoid reaction, peritumoural fibrosis, Dukes' stage, and relationship w ith adenoma, Mucinous cancers with DNA replication errors were charact erized by three features: onset in younger patients (P<0.05); exophyti c gross shape (P=0.03); and an expanding pattern of growth (P=0.003). Of the 12 mucinous carcinomas with instability in tao or more microsat ellites, ten (83.3 per cent) exhibited an expanding pattern of growth, while mucinous cancers with instability in one microsatellite or with out genomic instability showed no distinctive growth pattern, This stu dy confirms the relationship between microsatellite instabilities and mucin production in colorectal carcinomas, but shows that replication error RER-positive and RER-negative mucinous cancers differ in few cli nico-pathological features, These differences are only in part similar to those previously reported in RER-positive colorectal carcinomas. T hese data indicate that mucinous carcinoma of the large bowel could re present a histological subset separate from other histotypes. (C) 1997 by John Wiley & Sons, Ltd.