Colloid carcinoma arising in an anorectal fistula in Crohn's disease: a case report.

Carcinoma arising in a chronic anorectal fistula in Crohn's disease is rare, but the association has been reported in the literature. In most cases, it concerns a colloid carcinoma. Probably chronic irritation at either end of a fistula can trigger the degeneration of scar tissue into cancer. The diagnosis is difficult, due to lack of specificity of symptoms and signs, and is often delayed, resulting in a poor prognosis. A 70-year-old female, diagnosed with Crohn's disease at the age of 45, developed a pararectal colloid carcinoma in an anorectal fistula that had existed for years. She was treated with an abdominoperineal resection and adjuvant chemotherapy (5-fluorouracil and levofolinate) but died. A high index of suspicion and regular surveillance is recommended in chronic anorectal fistulas in Crohn's disease. In case of doubt, repeated biopsies should be performed to rule out malignancy.