[Adenocarcinoma in a tail-gut cyst: a rare cause of recurrent perianal fistula].

A 58-year-old woman was initially externally diagnosed in 1983 with a presacral mass, which was subsequently treated as an abscess. Thereafter, the patient experienced recurrent perianal fistulas. Further diagnostic studies revealed a cystic tumor, considered to be an epidermoid cyst, which was located in the inferior pelvis and was consequently removed. Histologically, cystic scar tissue was found with a highly differentiated adenocarcinoma which measured 4 cm. Later on, the patient again experienced perianal fistulas originating from a renewed presacral mass. As a result, an abdominal-perianal rectum extirpation and a partial resection of the sacrum with placement of a descendostomy were done. Histologically, adenocarcinoma tissue was found at the base of a tail-gut cyst. One year following her operation, the patient is free from any complaints and relapses. The tail-gut cyst is a very rare entity which arises from the inadequate involution of the tail-gut during embryonal development. A malignant transformation occurs in 10% of the cases. In the case of recurrent perianal fistulas and cystic masses between the rectum and os sacrum or os coccygeum, a tail-gut cyst should be taken into consideration, the goal being its complete removal.