NON-POLYPOID ADENOMA OF THE LARGE-INTESTINE

In order to find non-polypoid (flat) adenomas in the large intestine, one hundred and twenty-six consecutively resected large bowels were st ained with methylene blue or haematoxylin and examined using a stereos copic microscope with special attention to pit pattern abnormalities. The primary diseases were classified into familial adenomatous polypos is (FAP) in 9 cases, multiple adenomas in 2 cases, colorectal cancers in 90 cases, Crohn's disease in 5 cases, ulcerative colitis in 2 cases , constipation in 9 cases, diverticular disease in 3 cases and others in 6 cases, respectively. Thirty-five flat adenomas were detected in 1 4 colons (14/126=11%). Twenty-one flat adenomas were found in 9 non-FA P cases (7 colons removed for cancer and 2 for multiple adenomas) and the remaining 14 flat adenomas were found in 5 FAP colons. No flat ade nomas were found in any of the 25 colons removed for non-neoplastic di sease. Nine flat adenomas (26%) had a depressed shape. The mean age of the non-FAP cases was 57 years and that of the FAP cases was 29 years (P<0.005). The mean size of non-FAP flat adenomas was 6.1 mm and that of FAP flat adenomas was 3.1 mm (P<0.005). Non-FAP flat adenomas were more frequently right-sided than those in FAP. Epithelial dysplasia w as graded as mild in 31 (89%) and moderate in 4 (11%), respectively. M oderate dysplasia was found in non-FAP cases exclusively. These result s suggest that flat adenomas may be heterogeneous. The significance of these lesions is discussed.