Colitis cystica profunda: report of a case in which differentiation from rectal cancer was difficult.

Colitis cystica profunda is a benign condition that has been confused with carcinoma. This rarely recognized condition is characterized by submucosal cysts. Macroscopically, the ulcerated character of the mass suggests carcinoma. Microscopically, attenuation of the innocuous-appearing cyst linings may give the false impression of a mucus-secreting carcinoma. A case of colitis cystica profunda in which the macroscopic appearance was so suggestive of malignancy that operation was carried out is reported.