We report a unique case of intramucosal carcinoma in a tubulovillous adenoma arising from a single diverticulum.Endoscopic mucosal resection(EMR)was carried out successfully and completely with the assistance of laparoscopy.A 71-year-old man was admitted to our hospital because of melena and anemia.Emergent colonoscopy showed diverticulosis in the right-sided colon.However,endoscopy could not exactly detect the bleeding site.A flat elevated polyp was found within a single diverticulum located in the descending colon and diagnosed as an intramucosal carcinoma,as magnifying chromoendoscopy revealed a type Ⅳ pit pattern.As his diverticular bleeding repeated,a rightsided hemicolectomy was decided for treatment,the polyp within the diverticulum was also completely removed by EMR with the assistance of laparoscopy.Although a colonic perforation was detected immediately after EMR,the perforation was closed with endoclips intraluminally and also repaired laparoscopically from the serosal side.Histologically,the resected lesion was an intramucosal well-differentiated adenocarcinoma and the surgical margin was free of tumor.