[Hairy-cell leukemia with osteolytic bone changes]

Spontaneous bone fractures and/or focal osteolytic lesions were observed in three patients with morphologically and cytochemically confirmed hairy-cell leukemia 1-3 years after diagnosis and splenectomy. In a bone biopsy obtained from the body of the 12th thoracic vertebra light microscopy revealed a medullary osteopathy, the marrow cavities being infiltrated by a uniform population of rounded or slightly elongated cells. In addition, focal osteolytic lesions were observed on the trabeculae. Ultrastructurally, the cellular infiltrates consisted of reticulum cells, few mature and immature plasmocytes and numerous typical hairy cells with or without ribosome-lamella complexes. These observations demonstrate that hairy-cell leukemia may be associated with severe bone lesions similar to those observed in plasmocytoma. Moreover, these findings support the hypothesis that the hairy cell is a leukemic cell with B-lymphocyte properties.