THYMOPHARYNGEAL DUCT CYST - MR-IMAGING OF A 3RD BRANCHIAL ARCH ANOMALY IN A NEONATE

Third branchial arch anomalies are rare. The authors present a case re port of a neonate with a rapidly growing neck mass due to cystic dilat ion of a persistent thymopharyngeal duct, which is a derivative of the third branchial arch. The presence of thyroid and thymic tissue in th e cyst wall, the communication of the cyst with the piriform sinus, an d the relationship of the cyst to carotid vessels and the sternomastoi d muscle were consistent with the features of a thymopharyngeal duct c yst embedded in the thyroid gland.