Thymic hyperplasia in a patient with Graves' disease.

Hyperplastic changes of the thymus may be found in patients with Graves' disease. However, this rarely presents as an anterior mediastinal mass, particularly among adults. In this report, we describe a 32-year old woman with Graves' disease and hyperthyroidism. During medical evaluation and treatment for her hyperthyroidism, a large anterior mediastinal mass was incidentally discovered. A cytological study of the lesion via computed tomogram-guided fine needle biopsy could not make a definitive diagnosis and suggested the possibility of a thymoma, which led to a surgical exploration. However, the final pathological diagnosis of the surgically removed tissue was thymic hyperplasia. The relationship between Graves' disease and thymic changes is discussed.