A 49-year-old man with anemia was found in endoscopic examination to have a subpedunculated polypoid tumor in the descending colon. The top of the tumor was white, lustrous, and movable with almost normal mucosa. We suspected it as a cancer of the descending colon and conducted left hemicolectomy. Macroscopically, the tumor was 22×18 mm and elastically soft. Microscopically, it showed proliferation of uniform atypical lymphocytes with hyperchromatic unclei in the superficial layer of the tumor head. Singularly, the tumor had hyalinofibrous connective tissue in the center of the head and peduncle. Immunohistochemically, tumor cells were positive to T-cell markers (CD3, MT1) and negative to B-cell markers (L26, MB1). The tumor had invaded the submucosal layer without lymph node metastasis and was diagnosed as non-Hodgkin's lymphoma, diffuse medium cell, T-cell in LSG. This case case was extremely rare, since it involved the descending colon, was subpedunculated, was early lymphoma, and was T-cell.