Chronic anal fistulas are not rare; however, the development of a carcinoma in long-standing, perianal fistulas is rare. We describe a case of an 85-year-old man with multiple, recurring, perianal fistulas, extending to the natal cleft. The patient underwent en bloc resection of the fistulas which were in direct continuity with the middle rectum. Histological examination revealed a mucinous colonic adenocarcinoma. Abdominal CT and colonoscopy revealed an extramural residual rectal mass. The patient refused a radical colorectal operation. Three years later, because of fistula recurrence, he underwent loop sigmoidostomy and radical en bloc excision of the perianal fistula and rectum, with immediate reconstruction by bilateral gluteal flaps. The patient was discharged on the 12th postoperative day, refusing adjuvant radiotherapy. We present this rare malignant entity, successfully treated by staged operations and without any adjuvant therapy.