Intramucosal carcinoma of the small intestine arising in regional enteritis (Crohn's disease). Report of a case studied for carcinoembryonic antigen and review of the literature.

A case of carcinoma of the small intestine arising in a patient with regional enteritis (Crohn's disease) of the ileum is reported. The patient, a 54-year-old woman, had a 21-year history of regional enteritis which was treated intermittently with sulfasalazine and prednisone. Segmental resections of the ileum had been performed on two previous occasions. Because of recurrent low-grade intestinal obstruction, another segment of ileum was resected. The bowel demonstrated the typical gross and histologic appearance of regional enteritis. Histologic examination also disclosed a carcinoma that was confined to the ileal mucosa. This case is the first reported in which a small bowel carcinoma arising in regional enteritis has been found only in the mucosa. Adjacent to the carcinoma, the mucosa showed varying degrees of dysplasia consistent with the "precancerous" changes that have been described in inflammatory bowel disease. Using a peroxidase-antiperoxidase immunoperoxidase technique, carcinoembryonic antigen was identified in normal, hyperplastic, dysplastic, and carcinomatous mucosa, but the most intense staining was seen in hyperplastic and dysplastic cells. Carcinoembryonic staining, however, did not aid in differentiating between hyperplasia, dysplasia, and carcinoma because of an overlap in staining frequency and intensity.