Primary bone lymphoma.

Primary bone lymphomas are rare, even though secondary involvement of the bone marrow is a common event in systemic lymphomas. Most primary bone lymphomas are primary bone diffuse large B-cell lymphomas (PBDLBCLs) with a rare occurrence of follicular, marginal zone, anaplastic large cell, Hodgkin, and T-cell lymphomas. The PBDLBCL affects the middle-aged to elderly population, with a slight predominance in men. The patients present with bone pain, palpable mass, fractures, or neurologic symptoms. The metaphysis of bones is a common location of PBDLBCL. Morphologically, the lymphoma consists of a polymorphous mixture of small to large cells with multilobated nuclei, fine chromatin, and inconspicuous to prominent nucleoli. Differential diagnoses for PBDLBCL include chronic osteomyelitis, primary bone sarcoma, leukemic infiltrate, Ewing sarcoma, metastatic sarcomas, and carcinoma. Most PBDLBCLs are treated with combined radiotherapy and chemotherapy with good prognosis.