<prompt> Risk of carcinoma in ulcerative colitis:20 after 20 years35 after 30 years30 after 30 years50 after 30 years  <response>: Cumulative risk of cancer increases with duration of ulcerative colitis, reaching 25 at 25 years, 35 at 30 years, 45 at 35 years and 65 at 40 years The risk of malignancy in Crohns pancolitis is similar to UC pancolitis, i.e. 2 after 10 years, 8 after 20 years and 18 after 30 years approximately. 