Colorectal cancer in regional ileitis.

Six patients, with overt Crohn's disease of the small bowel developed colorectal cancer. Three distinct clinical patterns were observed. Three patients had advanced rectal adenocarcinoma and a relatively long duration of Crohn's disease, two patients had an early adenocarcinoma and a short antecedent history, and a sixth patient had advanced cloacogenic cancer of the anorectum. The prognosis for a patient with carcinoma in association with regional enteritis was poor when there was advanced disease at the time of diagnosis. The late diagnosis of the cancer may have been the result of three erroneous assumptions. First, scepticism as to the association of Crohn's disease and cancer despite the evidence to the contrary; second, misinterpretation of the intestinal symptoms of the carcinoma as those of the underlying inflammatory bowel disease; and third, confusing the clinical picture of colorectal cancer with that of benign perianal disease with stricture formation. Increased awareness of the association of cancer and Crohn's disease, particularly the development of cancer in apparently normal bowel, and careful evaluation of all new symptoms should improve the prognosis of this potentially lethal complication of inflammatory bowel disease.