Thymopharyngeal duct cyst: a form of cervical thymus.

The various types of cervical thymus may present as a neck mass, usually laterally, from the angle of the mandible to the manubrium. Since it is rare to diagnose the entity preoperatively, the differential diagnosis includes the more common branchial cleft cyst, thyroglossal duct cyst, cystic hygroma, cystic dermoid, and lesions of the salivary gland, thyroid, parathyroid, and cervical lymph nodes. Because cervical thymic tissue in various forms has been reported so frequently, we feel the entity should be considered in the clinical differential diagnosis of lateral neck mass, especially in the younger age group.