Aberrant thymus and parathyroid gland presenting as a recurrent lateral neck mass: a case report.

We report an interesting case of a recurrent left lateral neck mass in a 6-year-old boy. When the tumor failed to disappear after a course of antibiotic therapy, it was excised. Histologic study revealed that the encapsulated mass contained a parathyroid gland embedded within a histologically normal thymus. The presence of thymic and parathyroid tissue within a single capsule supports the idea that these two structures have a common embryologic origin. The combination of thymic and parathyroid tissue in a neck mass in a patient so young is rarely reported.