[Extramedullary hematopoiesis -- a differential diagnosis of intrathoracic paravertebral tumors]

Intrathoracic tumors always suggest a malignant clinical picture in the first instance. Especially in the case of paravertebral masses an extramedullary hematopoiesis is possible. It is regarded as compensation mechanism for reduced blood cell formation.

In four patients' radiographic examination of the lung partially bilateral paravertebral masses where detected by chance. In two cases, a chronic anemia existed, one patient suffered from an extended hemangiomatosis of the right brachium and the right hemithorax. In one case, no hematological disease could be diagnosed.

The computed tomography revealed malignancy-simulating tumors with partially necrotic pattern. In all cases, transthoracal biopsy showed cytological evidence of typical differentiated bone marrow with a regular hematopoiesis. As the extramedullary hematopoiesis of these four patients was diagnosed by chance and no symptoms or local complications existed, no specific therapy was necessary. In one of these cases a stable radiographic outcome for more than ten years is evident.

Especially in the case of patients with chronic anemia the existence of extramedullary hematopoiesis has to be considered upon occurrence of paravertebral tumors. An hematological disorder as cause may as well be absent. Due to the suspicion of malignancy a morphologic diagnosis is always necessary, but some clinical and radiologic features may indicate a benign process. A progression of the size can be unrecognized for ten years, so a therapeutic intervention is needed only in case of symptoms like myelocompression.