Fourth branchial cyst presenting with neonatal respiratory distress.

Fourth branchial cysts are quite rare. A neonate with a left lateral neck mass and respiratory distress was found to have a fourth branchial cyst, which was diagnosed with computed tomography and endoscopy. The characteristic computed tomography findings included an air-containing neck cyst, which was located at the anteromedial site of the common carotid artery with mediastinal extension. Endoscopic examination revealed an internal opening at the apex of the pyriform sinus, communicating with the cyst. Total excision of the cyst was performed, and the specimen, which showed ciliated columnar epithelium with a subepithelial lymphoid infiltrate, thyroid follicles, and thymic tissue, histologically confirmed the diagnosis.