Malignancy in Crohn's disease.

Cancer morbidity has been evaluated in a series of 513 patients with Crohn's disease under long-term review between 1944-76. In comparison with morbidity rates for cancer in the West Midlands Region (the geographical area from which these patients were drawn) the 31 tumours that occurred represented a relative risk of 1.7 (P less than 0.01) of cancer at all sites. For tumours at sites within the digestive system the relative risk was 3.3 (P less than 0.001). A significant excess of tumours was found in both the upper (P less than 0.01) and lower (P less than 0.001) gastrointestinal tract. There was no excess of tumours at any site outside the digestive system.