Following features are suggestive of:

(A) At low power, the abnormal plasma cells of multiple myeloma fill the marrow. (B) At medium power, the plasma cells of multiple myeloma here are very similar to normal plasma cells, but they may also be poorly differentiated. Usually, the plasma cells are differentiated enough to retain the function of immunoglobulin production. Thus, myelomas can be detected by an immunoglobulin ‘spike’ on protein electrophoresis, or the presence of Bence Jones proteins (light chains) in the urine. Immunoelectrophoresis characterizes the type of monoclonal immunoglobulin being produced. (C) Here is a smear of bone marrow aspirate from a patient with multiple myeloma. Note that there are numerous plasma cells with eccentric nuclei and a perinuclear halo of clearer cytoplasm. (D) The rounded ‘punched-out’ lesions of multiple myeloma appear as lucent areas with this skull radiograph.