Abstract

Anal duct carcinoma is a rare tumor, and accounts for less than 5 percent of all anal cancers, which typically present a long-standing perianal fistulas. Some authors suggest that the fistulous tracts are congenital duplications of the lower end of the hind gut lined by rectal mucosa which is prone to malignant change to mucinous adenocarcinoma. It is usually a well differentiated mucinous (colloid) adenocarcinoma. The prognosis after wide excision of the rectum is relatively good. Since 1985, we have had three cases of anal duct carcinoma with well differentiated mucinous adenocarcinoma involving the posterior wall of the anus. Two patients had a long history of perianal fistula with mucinous discharge. There was no spread to the regional lymph node except one patient who had regional lymph node metastasis, and post-operative chemotherapy and radiation therapy were then given. All patients have no evidence of any recurrent problem at 16 months to 3 years following the surgical treatment. Because of their rarity and the failure of recognition at an early stage, we are presenting three cases to emphasize the characteristic features of this insidious, slow-growing carcinoma.

• Keywords: Anal duct;Mucinous adenocarcinoma;Hindgut duplication;Perianal fistula