Risk of carcinoma in ulcerative colitis:

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 Crohn's pancolitis is similar to UC pancolitis, i.e. 2% after 10 years, 8% after 20 years and 18% after 30 years approximately.