Objective: Patients with ulcerative colitis are at increased risk for colorectal cancer, especially at younger ages. Our aim was to determine, in our patient cohort, the clinicopathological features, incidence, and prognosis of ulcerative colitis-associated colorectal cancer.

Methods: A single-center, population-based study including all 1241 patients with ulcerative colitis who underwent surgery in Helsinki University Hospital, 1991-2018. All data were from medical records, collected retrospectively.

Results: In total, 71 patients with ulcerative colitis-associated cancer were operated on in Helsinki University Hospital during 1991-2018; 108 patients undergoing surgery during 2002-2018 showed dysplasia in the surgical specimen. Cancer was diagnosed preoperatively in 47 patients (66.2%). Ten patients (14.1%) had synchronous colorectal cancer, and 24 (33.8%) had synchronous dysplasia. The incidence of colorectal cancer has not changed during the study period (p = .113). Overall survival was 71.8%, and the 5-year colorectal cancer-specific survival was 81.5%.

Conclusions: The incidence of ulcerative colitis-associated colorectal cancer remained constant in our study population over three decades. The prognosis of ulcerative colitis-associated colorectal cancer and the prognosis of sporadic colorectal cancer were comparable. One-third of the cancers were not diagnosed in preoperative colonoscopy, and the indication for surgery in such cases was dysplasia. We therefore do not recommend the endoscopic management of ulcerative colitis-associated dysplasia.