Perianal mucinous adenocarcinoma arising from a chronic fistula-in-ano.

Mucinous adenocarcinoma arising in a long-standing anorectal fistula is rare in clinical practice. Evidenced-based guidelines for treatment are lacking due to the rarity of this tumour. We present the clinical case of an advanced perianal mucinous adenocarcinoma associated with a longstanding perianal fistula, successfully treated by extended -abdomino-perineal resection, reconstructed by bilateral myocutaneous gluteus flaps, without any adjuvant therapy.