Multiple myeloma expressing CD19(+)CD56(-) phenotype

A 70-year-old woman presented with monoclonal gammopathy, pancytopenia, and renal insufficiency, which were initially refractory to combination chemotherapy by VMMD (vincristine, ranimustine, melphalan, and dexamethasone) and MP (melphalan and prednisolone) regimens. The myeloma cells, which consisted of 73% of bone marrow nucleated cells, expressed CD38(+), CD19(+), CD56(-), CD45(-), CD49e(-), and MPC-1(+) phenotypes by flow cytometric analysis and showed the rearranged immunoglobulin heavy chain (IgH) gene by Southern blotting. By immunostaining, the myeloma cells were positive for cytoplasmic immunoglobulin light chain kappa. These results suggest that myeloma cells can express CD19(+)CD56(-), the phenotype considered to be expressed on only normal plasma cells.