The histologic appearance of dysplasia (precarcinomatous change) in Crohn's disease of the small and large intestine.

Six patients with Crohn's disease and intestinal carcinoma are presented who demonstrated dysplastic changes in their intestinal mucosa. These changes were present adjacent to and/or distant from the infiltrating carcinoma and were extensive in 2 of these patients. The dysplasia affected many different cell types and was in many ways similar to that seen in ulcerative colitis. In view of the difficulties in making a clinical diagnosis of carcinoma in Crohn's disease, the finding of these changes on biopsy should be a strong indication for resection. However, as many of the carcinomas in Crohn's disease occur in excluded loops and in the small intestine, these changes will be of less value clinically than in ulcerative colitis, because access to these areas is difficult.