Thoracic extramedullary hematopoiesis associated with hereditary spherocytosis.

A 54-year-old man was diagnosed with hereditary spherocytosis. An X-ray of the chest disclosed bilateral round masses in the upper and lower posterior mediastinum. CT showed homogeneous round masses of soft tissue density in the posterior mediastinum. A needle biopsy of the mass showed hyperplastic erythroid bone marrow. Fatty metamorphosis of the masses was observed in CT 2 years after splenectomy but showed no change in size.