A CLINICOPATHOLOGICAL STUDY OF SMALL FLAT COLORECTAL-CARCINOMA

Background. Recent studies have noted that small flat carcinomas do ex ist in the human colon, but their clinicopathologic features have not been fully delineated. Methods. A clinicopathologic study of 62 flat c olorectal carcinomas (FCC) and 80 polypoid colorectal carcinomas (PCC) was performed. FCC were defined for the study as colorectal adenocarc inomas confined to the mucosa or submucosa, macroscopically characteri zed as slightly elevated, often nearly flat, and sometimes with centra l shallow depressions. Results. In intramucosal and submucosal invasiv e carcinomas, the mean size of FCCs was significantly smaller than tha t of PCCs, (P < 0.001). When compared with PCCs, FCCs were found more often in the proximal colon, less frequently well differentiated, and had fewer adenomatous remnants. In submucosal invasive cases, FCCs sho wed more frequent deep invasion (67 versus 32%, P < 0.05) and lymphova scular permeation (41% versus 16%, P < 0.05) compared with PCCs. Concl usions. These results suggest that FCCs are characterized by frequent deep invasion with lymphovascular permeation even when small, and that they may be more prevalent away from the rectosigmoid area.