Multiple myeloma: ‘early’ plasma cell phenotype identifies patients with aggressive biological and clinical characteristics

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Abstract
Summary. The immunological phenotype of bone marrow myeloma cells and peripheral blood lymphocytes was evaluated in 38 untreated myeloma patients. A striking increase of monotypic cells expressing the same light chain as the M component was observed in bone marrow from 18/38 (47%) patients. A two-colour analysis clarified that the majority of myeloma cells co-expressed plasma cell and B lymphocyte markers (cyIg, CD38, CD56 and sIg), and were regarded as early-plasma cells (early-PC). In the remaining patients, myeloma cells expressed plasma cell markers only (late-PC). Phenotype corresponded to a distinct morphological pattern: early-PC showed a lympho-plasmocytoid feature with significantly lower diameters than late-PC (12.1 v 14.8 μm, Pv 0.5%, P2-microglobulin, C-reactive protein and neopterin, showed a statistically significant increase in the early-PC patients, suggesting a poor outcome. In conclusion, myeloma cell phenotype allows identification of a myeloma variant with aggressive biological and clinical characteristics.