A case of appendiceal mucocele showing massive mucous production with concomitant colonic cancer.

A 58-year-old male patient presented with abnormal discharge of 200 ml transparent fecal mucus. Irregular protuberance of the ascending colon into the adjacent ileocecal region was observed by colonofiberscopy, and a cystic lesion in the ileocecal region was suggested by computerized axial tomography. Pale yellowish semitransparent jellied substances were observed exudating from the site of ileocecal resection. The diagnosis established was moderately differentiated colonic adenocarcinoma and a mucocele of the appendix. The mucus discharge disappeared after resection. Biochemical analysis of the mucus suggested the mucocele as a source of the discharged mucus. We report an extremely rare case of mucocele of the appendix that may be related to the cause of mucous stool.