A 90-year-old woman was admitted to our hospital because of dizziness, without any remarkable abdominal symptoms. Severe anemia was found and thus gastrointestinal investigations were performed. CT and ultrasonography showed the specific multiplex layer configuration at the anal side of the descending colon. Colonoscopy showed a round tumor occupying the lumen and a consecutive gastrografin enema showed a crab-claw-like area without filling in the descending colon. Intussusception of the colon was diagnosed and partial resection of the descending colon was performed, but without relief of intussusception. The tumor was histologically diagnosed as mucinous adenocarcinoma. By various factors, incomplete fixation between the retroperitoneum and the descending colon might result in the present condition.