A third branchial pouch cyst presenting as a lateral neck mass in an adult.

Anomalies of the branchial apparatus occur with some frequency in the adult and pediatric populations. Branchial anomalies are most often derivatives of the first or second pouch. Branchial anomalies involving the third pouch may present as cysts, sinuses, fistulas, and ectopic glands. They are relatively rare, and they respond well to surgical removal. We report the case of a 53-year-old woman who was referred to us for evaluation of a persistent left upper neck mass. The patient had no history of a cervical mass as a child or young adult. The mass was excised uneventfully, and the final pathology revealed a normocellular parathyroid gland and thymic tissue.