Adenocarcinoma arising from chronic perianal Crohn's disease: case report and review of the literature.

Perianal disease is a common manifestation of Crohn's disease. Rarely malignancy arises in perianal fistulas. The etiology of fistula related cancer remains a subject of debate. We present a unique case of a perianal Crohn's disease with adenomatous epithelialization of a fistula tract and an associated mucinous adenocarcinoma. Our case demonstrates that mucinous adenocarcinoma can arise in long standing perianal Crohn's disease and may be associated with adenomatous transformation of the epithelial lining of the fistula tract.