Solitary juvenile polyp of the rectum with intramucosal adenocarcinoma.

We describe a case of solitary juvenile polyp of the rectum with intramucosal adenocarcinoma. A 55-year-old man presented to our hospital for evaluation after a positive fecal occult blood test. Colonoscopy revealed a pedunculated polyp of 25 mm in size which has an irregular shape and pale red color on the rectum. The polyp had a proliferation of blood vessels and an invisible surface pattern. Endoscopic mucosal resection was performed. Pathologically, it was diagnosed as a solitary juvenile polyp with intramucosal well-differentiated adenocarcinoma. When we encounter juvenile polyps, the possibility of malignancy should be taken into consideration for treatment.