RESUMO
BACKGROUND: Chronic anal fistulas are not rare conditions, however, the development of a carcinoma in a long-standing fistula-in-ano is rare. METHODS: The case of a 77-year-old male with a large perianal mucinous adenocarcinoma arising in a long-standing fistula-in-ano is presented. RESULTS: Perianal biopsy revealed mucinous adenocarcinoma. Abdominal CT, double contrast barium examination and flexible sigmoidoscopy revealed no other tumoral lesion in the colon and rectum. CONCLUSION: The patient underwent abdominoperineal resection including wide tumor excision on the gluteal region. The final reconstruction was performed by bilateral gracilis musculocutaneous flaps. Due to clinical and histopathological evidence it was thought that a curative resection had been performed. To date he is clinically disease free.