Intramucosal Poorly Differentiated Adenocarcinomas Detected in a Patient with Long-Standing Ulcerative Colitis

We report a case of long-standing ulcerative colitis with intramucosal well- and poorly differentiated adenocarcinomas detected over a 6-month duration. A Japanese man in his sixties with a 31-year history of ulcerative colitis had a 1.1-cm-sized intramucosal well-differentiated tubular adenocarcinoma in the rectum resected by endoscopic submucosal dissection. At the follow-up colonoscopy, a biopsy near the endoscopic submucosal dissection scar revealed poorly differentiated adenocarcinoma, and a total proctocolectomy was performed 6 months after the endoscopic submucosal dissection. The whole colorectal pathological exam showed 2 flat foci of intramucosal poorly differentiated adenocarcinoma, 4 and 2 mm in size each, near the endoscopic submucosal dissection scar in the rectum, and an increased number of Paneth cells, thickened muscularis mucosa, and widening of the distance between the gland base and muscularis mucosa in the transverse colon to the rectum. Adenocarcinomas were not found in areas where architecturally severe changes of the mucosa or the highest number of Paneth cells proliferation were detected. Multiple biopsies using magnifying narrow band imaging or crystal violet staining around the initial high-grade dysplasia or intramucosal adenocarcinoma were effective to find other lesions, such as poorly differentiated adenocarcinoma foci in the mucosa in a long-standing ulcerative colitis patient.