[Plasmablastic lymphoma presenting clinical symptoms similar to plasmablastic myeloma].

A 75-year-old man developed multiple head masses as well as a compression fracture. His blood test revealed elevated immunoglobulin G (IgG) protein levels, and immunofixation electrophoresis revealed the presence of monoclonal IgGκ. Furthermore, positron emission tomography/computed tomography revealed multiple bone lesions, although bone marrow examination revealed only 1.2% of plasma cells. Biopsy of a head mass led to the diagnosis of plasmablastic lymphoma (PBL), an aggressive B-cell lymphoma with plasma cell phenotypes but no B-cell antigen expression. Because the tumor cells have plasmablastic morphologies, it is difficult to distinguish PBL from plasmablastic myeloma, which is a subtype of multiple myeloma. Both diseases have similar immunophenotypes and clinical courses. In this case, PBL was finally diagnosed based on Epstein-Barr virus positivity, and the patient made a complete recovery after treatment with DA-EPOCH.