Immunophenotypic Profile of Multiple Myeloma: A Tertiary Care Centre Experience

Background  Immunophenotyping and enumeration of plasma cells (PCs) by flow cytometry are deemed to be prognostically significant. However, PCs enumeration by flow cytometry is challenging owing to discrepancy with morphology and PCs loss during sample processing. Enumeration and differentiation of abnormal plasma cells (APCs) and normal plasma cells (NPCs) is difficult because abnormal antigen expression can be seen in subsets of NPCs. This is particularly true when a limited panel of antibodies are relied upon. Aims and purpose  To study the immunophenotypic profile of newly diagnosed multiple myeloma (MM) cases by flow cytometry and evaluate the sensitivities and specificities of individual antigens and combinations. Methods  We studied immunophenotype of PCs in newly diagnosed MM cases ( n  = 48) and control cases ( n  = 10) by a 6-color, 3-tube flow cytometry panel. The sensitivities and specificities of antigens in MM were evaluated and compared with control cases. Results  Majority of MM cases ( n  = 43) had < 3% NPCs. CD19 was the most sensitive (100%) and CD81 was the most specific marker (100%) for differentiating APCs from NPCs. CD38 MFI came out as a useful marker for APCs identification. In combination, CD19 and CD81 had a higher sensitivity and specificity to detect APCs. Conclusion  NPCs may show aberrant antigen expression. A combination of multiple markers including CD81 and CD38 MFI should be used for accurate APC detection.