[Ulcerative Colitis-Associated Cancer Resembling a Submucosal Tumor-A Case Report].

A 63-year-old man was diagnosed with ulcerative colitis of the proctitis type 12 years ago. Three years ago, his symptoms worsened and he was diagnosed with pancolitis type. Recently, a colonoscopy revealed a stenotic lesion with a submucosal tumor-like protrusion in the rectum. Biopsy of the same area did not reveal any neoplastic lesion. However, because 18F-fluorodeoxyglucose accumulation was observed in the stenotic lesion and the value of carcinoembryonic antigen increased over time, the patient was diagnosed with rectal cancer(cT3N0M0)associated with ulcerative colitis. Robot-assisted low anterior resection was performed. Postoperative histopathological examination revealed a submucosal tumor-like invasive carcinoma in the stenotic lesion with intramucosal lesion corresponding to UC-Ⅲ. Currently, 2 years after surgery, the patient shows no evidence of disease recurrence.