[1475] Immunophenotypic Heterogeneity of Normal Plasma Cells

Dingsheng Liu, Pei Lin, Ying Hu, Linda Powers, Jeffrey L Jorgensen, Sa A Wang. MD Anderson Cancer Center, Houston, TX

Background: Plasma cell neoplasms exhibit various immunophenotypical aberrancies that can be used for minimal residual disease detection. We questioned whether normal plasma cells, especially in the bone marrow post various treatments, would show immunophenotypical variations overlapping with neoplastic plasma cells.
Design: Using multicolor flow cytometry, we studied the immunophenotype of plasma cells from 12 negative pre-treatment lymphoma staging bone marrows and 38 bone marrows from patients with other non-plasmacytic hematological malignancies undergoing various therapies. Cases with incidental clonal plasma cell proliferations as demonstrated by cytoplasmic light chain expression were excluded.
Results: The non-neoplastic plasma cells were consistently positive for CD45 [78% (40.7-100)] and CD19 [78.9% (51.9-97.1)] but the expression levels were heterogeneous within the plasma cell population. CD20 [3.9% (0-21.1)] and CD117 [0.5% (0-10.9)] were reliably negative in the majority of the cases. CD56 expression was observed in a small subset of plasma cells [5.8% (0-23.7)]; whereas CD28 was positive in a larger subset [15% (1.5-59.2)]. Interestingly, these aberrancies were rarely observed in the same subset of benign plasma cells within a single specimen. We compared the 38 post-treatment bone marrows to 12 bone marrows without treatment. CD19, CD20, CD45 and CD56 expression levels were comparable; however, CD28 expression was significantly increased (p=0.01).
Conclusions: Normal plasma cells are more immunophenotypically heterogeneous than we previously understood; however, these immunophenotypic variations differ from a true plasma cell neoplasm which often exhibits 2 or more abnormalities in the same cells. Some therapeutic agents appeared to up-regulate CD28 expression whereas other markers were not affected. These findings provide an important reference for minimal residual disease detection by flow cytometry.
Category: Hematopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 232, Wednesday Afternoon


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