Mucinous adenocarcinoma derived from chronic perianal fistulas: report of a case and review of the literature.

Chronic perianal fistulas are a common clinical condition. However, their evolution into adenocarcinoma is rare. We report the case of a 68-year-old man with perineal and perianal chronic fistulas, who developed a perineal mass that extended proximally as a pararectal tumor. Diagnosis was confirmed by magnetic resonance imaging (MRI). Histopathological sections indicated extramucosal mucinous adenocarcinoma. No intestinal lesion was seen at endoscopic examination. The patient underwent abdominal perineal excision of the rectum without neoadjuvant or adjuvant therapy, and had a good postoperative outcome.