Thoracic extramedullary hematopoiesis in sickle-cell disease.

The radiographic manifestations of thoracic extramedullary hematopoiesis are unilateral or bilateral, smooth, sharply delineated, often lobulated paraspinal masses without erosion of the vertebral bodies or ribs, sometimes associated with subpleural, paracostal masses. These radiographic findings were encountered in eight adult patients with homozygous sickle-cell disease. In one patient, the masses encompassed essentially the entire thoracic paravertebral area bilaterally. In the other seven patients, the masses were unilateral and limited to the region of the eighth to the 12th thoracic vertebrae. Two of the eight patients had lateral subpleural masses that were not contiguous with the paraspinal masses and that were located medial to the lateral portions of the ribs. Follow-up in seven of the cases ranged from 2 to 15 years and demonstrated, after relatively rapid growth initially, either no change in size or slow growth. Each patient was asymptomatic with regard to the thoracic masses. Histologic verification was not available in any case because of the lack of clinical indication for invasive diagnostic or therapeutic procedures. The presence of well-defined unilateral or bilateral paraspinal masses and/or paracostal masses in patients with homozygous sickle-cell disease and without related symptoms should alert one to the possibility of the presence of extramedullary hematopoiesis. These masses tend to be slow-growing and should not be subjected to aggressive diagnostic and therapeutic measures.