A Case of Ascending Colon Cancer Probably Arising from a Diverticulum

: A 70's male was admitted to our hospital with complaints of anorexia and abdominal pain. CT showed thickening of the ascending colon. Colonoscopy revealed multiple diverticula of the ascending colon, but no tumor on the mucosa. The patient was diagnosed as a case of diverticulitis of the ascending colon and was advised laparoscopic ileocecal resection. The resected specimen showed wall thickening; however, no remarkable findings were observed, with the exception of multiple diverticula on the mucosal surface. Histological examination showed well-differentiated tubular adenocarcinoma extending into the serosa probably arising from the diverticulum. Chemotherapy was performed after surgery. The patient died due to peritoneal dissemination from the ascending colon cancer 14 months after surgery.