Small depressed neoplasms of the large bowel: radiographic visualization and clinical significance.

Small depressed and flat neoplasms (small flat adenomas) exist-in the large bowel and in the stomach. Most have been detected with colonoscopy. We tried to delineate these lesions radiographically. Radiographically, the contour of the lesions measuring 5 mm and less was visualized in 32 (60.4%) of 53 lesions. Radiographic examination preceded colonoscopy in 23 (71.9%) of these lesions. Ten (83.3%) of 12 lesions measuring 6-10 mm were visualized. The central depression was clearly delineated in 32 (60.4%) of 53 lesions measuring 5 mm and less and in 5 of the 12 (41.7%) lesions measuring 6-10 mm. The central depression was not demonstrated in all lesions whose contours were not visualized. The clinical significance of the small depressed neoplasm lies in the fact that a certain number may be a precursor of rapidly growing carcinoma with early submucosal invasion.