The unusual presentation of mucinous carcinoma in the colon making preoperative diagnosis difficult: report of a case.

A 51-year-old man was admitted to our hospital for investigation of fever, lower abdominal pain, and pain on micturition. Barium enema and endoscopic findings revealed an extracanal large cavity of the rectosigmoid colon, which suggested an abscess caused by penetration. Histological examination of the endoscopic biopsy specimen demonstrated no malignancy. A preoperative diagnosis of malignant lymphoma was strongly suspected from the imaging findings; however, intraoperative inspection revealed a large tumor invading the urinary bladder. An intraoperative incisional biopsy was performed and histological examination demonstrated mucinous carcinoma. The patient subsequently underwent pelvic exenteration about 1 week later followed by adjuvant chemotherapy and radiotherapy.