[A case of carcinoma arising from an anal fistula].

Carcinoma arising from a chronic anal fistula is an uncommon condition. A 53-year-old woman visited our clinic, complaining of refractory anal fistulas that had persisted for over a period of 15 years, which had started to discharge pus and mucus through external fistulous openings several months ago. A cytologic study of the perianal discharges and a biopsy of the external openings were useful in preoperatively detecting a cancer complicating an anal fistula. An abdominoperineal rectal amputation with an extended dissection of the relevant lymph nodes was performed. Histopathological findings revealed a mucus-producing adenocarcinoma with ly1, v0 in vessel invasion, and the stage of cancer was determined as being stage II, H0P0a2n0 (0/129). It is emphasized that cancer should be suspected whenever examining an old fistula, especially one with mucous discharges.