Plasma Cell Leukemia - Laboratory Findings

Laboratory Findings

Although there is overlap, the markers of plasma cells from patients with primary PCL is different from those of myeloma patients. PCL plasma cells more frequently express the CD20 antigen than those of multiple myeloma (50% vs. 17%), and they often lack CD56 antigen which is present on the majority of myeloma cells. CD56 is considered important in anchoring plasma cells to bone marrow stroma, and its expression is associated with a poor prognosis. CD28 is more frequently expressed on malignant plasma cells in secondary than in primary PCL, which is consistent with an observation made in myeloma, that is, that acquisition of the CD28 antigen on plasma cells appears to correlate with an increased proliferative rate and disease progression.

The chromosome characteristics or karyotypes of PCL plasma cells is complex. Using fluorescence in situ hybridization ( fish ) techniques, losses in the long arm of chromosome 13 (13q) and deletion of one the homologous chromosomes 13 (monosmy 13) exist in more than 80% of PCL patients. Losses on chromosome 16 also occur in approximately 80% of cases. Gains in long arm of chromosome 1 (1q) are present in approximately one-half of the patients determined by FISH, but in all patients by comparative genomic hybridization. Overexpression of the protein PRAD1/cyclin D1, which plays an important role in control of the cell cycle, has also been observed in PCL. Plasma cell leukemia is more frequent in light-chain (Bence Jones protein) or IgD myeloma. It is seen less frequently in IgA or IgG myeloma (see: multiple myeloma).