Anterior mediastinal mass in a patient with Graves' disease.

Thymic hyperplasia is a common feature in Graves' disease. However, in most cases, thymic enlargement is minimal, and radiologically detectable massive enlargement of the thymus is infrequently reported. Half of them undergo thymectomy due to the concern about a thymoma. We report a 28-year-old woman with untreated Graves' disease. She had an anterior mediastinal mass that was diagnosed as true thymic hyperplasia by biopsy and disappeared after treatment of the hyperthyroid state. Recognizing the association between thymic hyperplasia and Graves'disease, and existence of the benign course after treatment of the hyperthyroidism may be useful for avoiding unnecessary surgical procedure.