We describe the clinical and morphological features of a most unusual functional mediastinal tumor that combines features of thymolipoma and lipoadenoma of the parathyroid gland. The lesion was unique in that microscopic elements of benign thymic, adipose, and parathyroid tissue were admixed intimately in one partially encapsulated mass. To the best of our knowledge, there has not been a previous description of this tumor. It was excised from a 54-year-old woman with a 10-year history of persistent hyperparathyroidism. The controversial relationship of embryological malformation, hamartoma, and neoplasm is exemplified by this entity.
