Abstract
A 62-year-old man was referred to our hospital for positive fecal occult blood. Colonoscopy showed a tumor consisting of a ha +IIc and ha parts in the ascending colon. This tumor did not have the character of collision tumor histopathologically. The part of superficial depressed type (ha +IIc) was diagnosed as moderately-differentiated adenocarcinoma with submucosal invasion (sm2). However, the part of superficial elevated type (ha) was diagnosed as well-differentiated adenocarcinoma with intramucosal lesion (m). Intramucosal lesion consisting of well-differentiated adenocarcinoma remained in the margin of type ha + IIc tumor. Considering these findings in the developmental pattern of this carcinoma, the part of superficial elevated type (ha) may be transformed from well-differentiated to moderately-differentiated adenocarcinoma at the mucosal stage which possessed malignant potencial, invaded submucosally and elevated the surrounding normal mucosa, leading to type IIa+IIc in shape. Therefore, we speculate that this tumor developed from superficial elevated carcinoma despite of the superficial depressed carcinoma on macroscopic appearance.
