DEPRESSED ADENOMAS OF THE COLON IN FAMILIAL ADENOMATOUS POLYPOSIS - HISTOLOGY, IMMUNOHISTOCHEMICAL DETECTION OF PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA), AND ANALYSIS OF THE BACKGROUND MUCOSA

Depressed adenomas of the colon have been reported more often during t he past several years, but there are few reports on the details of the ir characteristics or behavior. In this study, depressed and ordinary polypoid adenomas, especially those in an early stage, in the large in testine of 28 patients with familial adenomatous polyposis (FAP) were examined macroscopically, by dissecting microscope, and histologically . Proliferating cell nuclear antigen (PCNA) and the density of crypts in the background mucosa around depressed and polypoid adenomas were a lso compared. Depressed adenomas of <1.0 mm in diameter showed horizon tal growth between the normal adjacent crypts, which often left the no rmal crypts as islands, whereas polypoid adenomas grow expansively wit hout including remnants of normal crypts. In depressed adenomas, PCNA shifted to the upper part of the crypts, and the background mucosa in their vicinity showed a low density of crypts. These findings indicate that a unique characteristic of growth of depressed adenomas at an ea rly stage is superficial proliferation.