We report an extremely rare case of a complete congenital third branchial arch fistula in a nine-year-old boy.

A case report and a review of the English literature concerning third branchial arch fistula of congenital origin are presented.

A nine-year-old boy presented with a history of a small opening in the middle third of the anterior neck since birth, with recurrent surrounding swelling. There was no history of surgical drainage or spontaneous rupture. Computed tomography with contrast injection into the external cervical opening revealed a patent tract from the neck skin to the base of the pyriform sinus. Complete excision of the tract up to the pyriform sinus with left hemithyroidectomy was performed. Follow up at 22 months showed no recurrence.

To our knowledge, this case represents a very rare occurrence of the congenital variety of complete third branchial arch fistula at an unusual site. This case indicates that third branchial arch fistula can be complete, and may present in the anterior neck, an unusual site. In such cases, computed tomography fistulography and injection of dye into the pyriform sinus enables intra-operative delineation of the tract.