[Preliminary study of immunophenotype of multiple myeloma cells]

Using the alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique, plasma cells from multiple myeloma (MM, 23 cases), plasma cell leukemia (PCL, 2 cases) and reactive plasmacytosis (RP, 13 cases) were immunophenotyped with a panel of monoclonal antibodies (McAb). The results showed that McAbCD38 was strongly positive in high percentage of MM and RP cases and the CD9 was the next. 9/23 MM expressed CD10. Our results might indirectly support that CD10 is a malignant marker of MM with poor prognosis, a concept proposed by Durie. The results were (1) all RP but 1 acute monocytic leukemia related to RP were CD10 negative. (2) In our series 2 cases of plasma cell leukemia (PCL) expressed CD10; (3) 4 MM cases survived more than 2 years were CD10 negative. A few MM cases also expressed other surface markers of pre-B and B lymphocyte, such as CD19, CD20, CD22, HLA-DR, cytoplasmic mu chain. CD20 was positive in 4/21 MM and negative in all RP cases. 7/22 MM expressed HLA-DR, and 1/13 RP did so, among them there was a significant difference. HLA-DR seems to be another malignant marker of plasma cells. 1 MM expressed CD8, and 1 PCL highly expressed CD4 indicating PCL might be heterogeneous. Lymphoid stem cells may be involved in MM and PLC. We conclude that multiple myeloma cells have different immunophenotypes and CD10, CD20 and HLA-DR may help to differentiate MM from RP.