Mucinous carcinoma in Crohn's disease originating in a fistulous tract.

Malignant disease, including mucinous carcinomas of the colorectum, may complicate long-standing Crohn's disease. An 18-year-old male with extensive small and large bowel involvement with Crohn's disease developed recurrent peri-rectal fistulous disease that persisted for more than a decade despite pharmacological and surgical therapy as well as later therapy with biological agents. Eventually, an extensive and difficult-to-detect mucinous carcinoma developed in the fistulous tract.