Hematological malignancies and the bone (myeloma excluded)

Bone involvement is a rare event in lymphomas, except in patients with adult T-cell leukemia/lymphoma associated with HTLVI. It is usually characterised by lytic bone lesions located in the metaphysis of long bones or in the axial skeleton. The occurrence of bone lesions reflects a progression of the disease affecting the prognosis that is related to lymphoma histologic features and staging. Bone lesions may occur in some lymphoproliferative disorders such as LLC or Waldenstrom's disease, or in myeloproliferative disorders. They may reflect a progression to a more aggressive disorder with a worse prognosis. The treatment of hematologic malignancies presenting with bone lesions and/or hypercalcemia is similar to the treatment of the systemic disease. In primary lymphomas of bone presenting with an isolated bone lesion, local treatment with radiation therapy and/or surgical ablation is required, and adjuvant chemotherapy may improve the prognosis of these located lymphomas. Glucocorticoid therapy and bisphosphonates are effective in treating associated hypercalcemia. Except for myeloma and ATL, the underlying mechanisms responsible for bone involvement in hematologic malignancies remain poorly understood. The unusual occurrence of bone lesions in these diseases probably implies distinct pathogenic mechanisms, but one can speculate that an increased expression of RANK/RANKL, the common final pathway in bone resorption, may be involved.