MULTIPLE-MYELOMA - EARLY PLASMA-CELL PHENOTYPE IDENTIFIES PATIENTS WITH AGGRESSIVE BIOLOGICAL AND CLINICAL CHARACTERISTICS

The immunological phenotype of bone marrow myeloma cells and periphera l blood lymphocytes was evaluated in 38 untreated myeloma patients. A striking increase of monotypic cells expressing the same light chain a s the M component was observed in bone marrow from 18/3 8 (47%) patien ts. A two-colour analysis clarified that the majority of myeloma cells co-expressed plasma cell and B lymphocyte markers (cylg, CD38, CD56 a nd sIg), and were regarded as early-plasma cells (early-PC). In the re maining patients, myeloma cells expressed plasma cell markers only (la te-PC). Phenotype corresponded to a distinct morphological pattern: ea rly-PC showed a lympho-plasmocytoid feature with significantly lower d iameters than late-PC (12.1 v 14.8 mum, P<0.007). Moreover, the plasma cell labelling index was significantly increased in early-PC patients (1.2 v 0.5%, P<0.04). In peripheral blood from patients with early-PC , monotypic cells co-expressing sIg and CD38, CD56, but not CD19, were also detected. These data suggest a recirculation of early-PC. Myelom a cells maintained their phenotypic pattern during the course of the d isease. This observation suggests that the degree of maturation is an intrinsic characteristic of the myeloma cell population in individual patients. The evaluation of prognostic factors, such as beta2-microglo bulin, C-reactive protein and neopterin, showed a statistically signif icant 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.