LETTER TO THE EDITOR Concomitant plasmacytoma and B cell lymphoma with discordant light chain expression but clonal identity

A 63-year-old patient presented with abdominal pain. A computerized tomogram scan showed a gallbladder mass (Fig. 1a). A positron emission tomogram revealed addi-tional FDG-avid lesions in the sternum, ribs, bilateral humeri, vertebral column, and pelvic bone (Fig. 1b). Magnetic resonance imaging confirmed vertebral lytic lesions (Fig. 1c). A serum protein electrophoresis showed a monoclonal band (IgA l 16.2g/l), and he was referred for suspected plasma cell myeloma (PCM). A bone mar-row biopsy, however, showed 19 % infiltration by mono-clonal B cells, expressing CD20, but negative for CD3−, CD5, CD10, CD138, IgA, IgG, and IgM (Fig. 1d). These cells showed κ−light chain restriction (Fig. 1e, f). Stain-ing with CD138 highlighted less than 1 % plasma cells, while the lymphoma cells do not express CD138. I