Importance of flow cytometry assessment of circulating plasma cells and its connection with clinical characteristics of primary and secondary plasma cell leukemia

Background Plasma cell leukemia (PCL) is a rare and very aggressive plasma cell (PC) disorder characterized by the presence of circulating plasma cells (cPC) in peripheral blood (PB). Dismal outcome of PCL requires early diagnosis with appropriate analytical tools. Development of flow cytometry (FC) together with some newly analysed antigens may reveal some marker affecting the prognosis of PCL patients. Aim Analysis of phenotypic profile of cPC/PCs to find association with clinical outcomes and to evaluate the prognostic value of analyzed markers. Methods Total of 33 primary and secondary PCL patients were investigated. PCs quantity and phenotype profile was analysed by polychromatic FC in PB and bone marrow (BM). Results Flow cytometry is an excellent method for cPCs identification as a significantly higher number was identified by FC than by morphology. Thus FC should be incorporated as a diagnostic method for preventing late diagnosis of PCL. Although the phenotypic profile of both PCLs did not differ too much, with low level of CD19, CD20, CD27, CD28, CD81 and CD117 expression, some heterogeneously expressed antigens (CD44, CD56, CD200, nestin etc.) may contribute to identification of patients with later extramedullary involvement, high risk of progression and shortened survival. Conclusions FC should be incorporated in PCL diagnostics as not only exact method providing number of cPCs, which is surprisingly overcoming morphology assessment. Moreover, PCL phenotype profile could be connected to patient’s diagnosis and possible prognosis as well. Funding Supported by grant AZV NV18-03-00203.