Immunophenotyping Of Plasma Cells

Immunophenotyping is a valuable technique for differentiating myeloma and normal plasma cells, and the distinction is based on the presence of phenotypic aberrations in myeloma plasma cells (MPCs) that are absent in normal plasma cells.

Normal plasma cells meet the following criteria on phenotyping: high-intensity CD38 positive, CD138 positive, CD 56 negative, CD19 positive, CD20 negative, CD28 negative, CD33 negative, and CD117 negative. Plasma cells in patients with myeloma may demonstrate other abnormalities; for example, positive CD20, CD40, and CD56, and negative CD19.8-11

Thus, although plasma cells are usually defined by high-intensity florescent CD38 and are CD45 negative, CD45+ populations of plasma cells have also been studied, and these correlate with plasma cell matrixity

Immunophenotype Plasma Cell
Figure 81.3 Bone marrow aspirate of a patient with IgA myeloma. "Flame" cells are typically associated with IgA myeloma. They are plasma cells which stain eosinophilic pink in the periphery of the cytoplasm due to the accumulation of Ig

and proliferative capacity. Immature plasma cells are CD38++, CD45 ++, have high labeling indices, and correlate with the clinical behavior of the disease.12 Mature malignant plasma cells are CD45 negative, have lower labeling indices, a lower incidence of P-glycopro-tein expression, and oncoprotein abnormalities.13

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