MINUTE SUPERFICIAL‐TYPE DE NOVO COLORECTAL CARCINOMA WITH SUBMUCOSAL INVASION

Abstract

A 59‐year‐old male was evaluated at the Foundation for Detection of Early Gastric Carcinoma after 4 years, following partial sigmoidectomy for early invasive cancer. Double‐contrast barium enema study and endoscopy revealed a new minute flat‐elevated lesion with an irregular central depression in the proximal sigmoid colon. Endoscopic mucosal resection was carried out with suspicious diagnosis of intramucosal colonic cancer. Macroscopically, the specimen constituted a flat‐elevated lesion measuring 4 mm in its largest diameter with a shallow irregular depression. Histologically, various‐sized vesicular nuclei and cribriform glands without adenomatous component were confirmed. A very small part of the lesion invaded into the submucosal layer. The diagnosis of carcinoma was made based on those histological findings, and this case was regarded as a minute superficial‐type de novo carcinoma. Radiographic and endoscopic findings were compared with the histological features in detail. Carcinoma was found at the depressed area on the surface of the lesion. Furthermore, the invasion of high‐grade carcinoma into the submucosal layer was located just beneath the deeper peripheral part of the depression which showed by colonoscopy. Consequently, a distinct depression on a flat‐elevated lesion may represent not only the presence of de novo cancer but also possible involvement of the deeper invasion.