Abstract: Objective To explore the immunophenotype characteristics and clinical significance of circulating tumor plasma cell （CTPC） in patients with multiple myeloma（MM）. Methods 75 newly diagnosed MM patients in our hospital were retrospectively analyzed. The immunophenotype and quantitative correlation of peripheral blood （PB） and bone marrow（BM） samples were detected by ten color flow cytometry. The MM patients were divided into CTPC positive group（CTPC+）and CTPC negative group （CTPC-）. Results There was a positive correlation between CTPC and the proportion of mono-clone plasma cells in BM（γ=0.536 8,P<0.000 1）,but there was no significant difference between CTPC+ group and CTPC- group（P=0.08）.Compared with CTPC- group,the expression of CD19 in mono-clone plasma cells in CTPC+ group was significantly decreased（P=0.029）,the expression of CD81 was significantly increased（P=0.006）,and the expression of Kappa,Lambda,CD56 and CD117 was not significantly different（P>0.05）. There was no significant difference between CTPC and BM mono-clone plasma cells in the expression of Kappa,Lambda,CD19,CD56,CD81 and CD117（P>0.05）. The serum level of β2-MG and the number of genetic high risk groups in CTPC-group were significantly lower than those in CTPC+ group,but there was no significant difference in CR between the two groups. Conclusion CTPC could reflect the load of intramedullary tumor cell. The low expression of CD19 and high expression of CD81 in BM clonal plasma cells are correlated with BM infiltration into peripheral system.

Key words: Multiple myeloma, Circulating tumor plasma cell, Immunophenotype, Multi-parameter flow cytometry