Significance Of Immunophenotype And Chromosome In Multiple Myeloma

Background and Objective: Multiple myeloma (MM), a malignant tumor of plasma cells, is characterized by the abnormal proliferation of monoclonal plasma cells, inhibition of hematopoieses and production of monoclonal immunoglobulin (Ig) or light chains. The clinical manif- estations are various and easy to be misdiagnosed or missed. The diagnosis mainly depends on marrow aspiration and biopsy. Sometimes it is difficult to obtain adequate marrow samples that contain enough myeloma cells to make the diagnosis and myeloma cells are difficult to distinguish with normal plasma cells by means of morphology. Therefore immunophenotype is necessary for helping to identify the lineage of myeloma cells, carrying on the supplement to the morphology inspection. CD45/Side scatter (SSC) flow cytometry is usually used to identify neoplastic plasma cells. By this way we can understand the biological behavior in a deeper way and suggest antibody-based targeted therapies. Cytogenetics is an independent factor for the prognosis of hematologic tumors. But up to now, there is no large sample report of MM chromosome karyotype analysis. Surface antigens and cytogenetic test provide evidences for early diagnosis, treatment and prognosis of MM.Methods: Samples of recently hospitalized 28 MM patients were collected. 18 samples were tested by flow cytometry. According to Durie- Salmon staging system there were 5 cases in stageⅠ, 3 cases in stageⅡ, 10 cases in stageⅢ. Among those 18 patients, 12 were de nova, 6 were relapsed. Fresh bone marrow samples were obtained. Heparin was added as anti-coagulation agent. CD45/Side scatter gating tri-coler immunofluorescence flow cytometry was used to test immunophenotype. Surface antigens CD138, CD38, CD56, CD117, HLA-DR, CD3, CD7, CD13, CD33, CD19, CD20, CD22 and CD34 were detected. Chromosome karyotypes were detected in 26 patients by R-banding method. There were 5 cases in stageⅠ, 6 cases in stageⅡ, 15 cases in stageⅢaccording to Durie-Salmon staging system.Results: The immunophenotype finding showed that the percentage of target cells in flow cytometry using CD45/side scatter gating (12.09%- 65.54%) was according with morphology finding of bone marrow (14%- 68%). The antigen expression of MM cells was regarded as positive if it was more than 20%. The positive rate of CD138 was 60.12%, CD38 was 100%, CD56 was 46.67%, CD13 was 70.59%, CD33 was 58.82%, HLA-DR was 70.59% and other antigens were negative. Chromosome analysis showed that 8 of 26 patients had abnormal karyotypes, rate of abnormality was 30.8%, and 6 patients had complex chromosomal aberrations. 2 of the patients with chromosomal abnormalities were in stageⅡ, 6 were in stageⅢ. The 8 patients with chromosomal abnormalities had obvious ostealgia, theirβ2-microglobulin level was 10.15±3.70mg/L (Reference value was 1.28-1.96 mg/L).β2-microglobulin level of the 18 normal karyotype patients was 5.03±3.84mg/L, the difference between two groups was significant.Conclusions:1. Phenotype using CD45/side scatter gating can clearly identify and characterize myeloma cells. The percentage of myeloma cells detected by this method is similar to the outcome of morphology findings.2. MM cells express some antigens, such as CD138 and CD38. CD138 is specific to MM. Antigens of B-lineage and T-lineage are not expressed on MM cells.3. In our study, rate of chromosomal abnormality in MM cells is 30.8%, complex chromosomal aberrations always occurs in stageⅢpatients.β2-microglobulin level of these patients increases obviously. Conventional cytogenetics is an independent prognostic factor.