The malignant potential of colorectal Crohn's disease.

Six patients developed colorectal carcinoma in association with Crohn's disease. The cancer was diagnosed at a mean age of 46 years and a mean 19 years after the onset of Crohn's disease. Five carcinomas arose in the chronically inflamed segment of bowel, while a sixth arose in caecum previously bypassed for Crohn's ileitis. Four carcinomas were mucinous, four presented with fistula and four were treated by complete removal of the large intestine. Three patients have died of residual or recurrent cancer. The data support an aetiological link between Crohn's proctocolitis and carcinoma.