Serial section study of colonic adenomas with special reference to minute carcinoma.

A total of 73 colonic adenomas, 20 with mild atypia, 26 with moderate atypia and 27 with focal carcinoma (severe atypia), were examined by complete serial section in order to find the distribution of various degrees of atypia in adenomas. In serial sections minute carcinomatous foci were found in 3 (15%) and 12 (46.2%) of the adenomas with mild and moderate atypia, respectively. Fourteen adenomas (51.9%) with focal carcinoma had multiple foci of minute carcinoma elsewhere. Adenomas less than 1 cm in diameter showed 27% malignancy rate in serial sections. From this observation it is postulated that the malignant potential of colonic adenomas is much higher than previously believed.