Phenotype of plasma cells in multiple myeloma and monoclonal gammopathy of undetermined significance

Flow cytometry is a useful tool for the analysis of plasma cells in monoclonal gammopathies. The aim of this study was to find possibilities and limits of multicolour flow cytometry in diagnostics of monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) and to identify parameters that could be used to differentiate between these two disorders. Surface markers CD38 and CD138 were used for identification of plasma cells, CD19 and CD56 further distinguished normal and abnormal plasma cells, respectively. The percentage of circulating plasma cells in peripheral blood was lower in MGUS patients then in MM (p<0,001). In bone marrow, the percentage of residual polyclonal CD19(+) plasma cells was higher (p<0,001) and the percentage of malignant monoclonal C1356(+) plasma cells was lower (p<0,001) in MGUS than in MM. The relative counts of CD19(+) plasma cells permitted unequivocal differentiation of MGUS from all clinical stages of MM. In conclusion, flow cytometry is relatively quick and effective method for analysis of plasma cells thus immunophenotyping can significantly contribute to the differential diagnosis of plasma cell proliferations.