Immunophenotypic Profile of Plasma Cells as Assessed by Multi-Color Flow Cytometry: A Comparison between Lymphoplasmacytic Lymphoma and CD45 Positive Myeloma
Sergej Konoplev, Sa A Wang, Jeffrey L Jorgensen, Tian Tian, David P Ng, Pei Lin. The University of Texas MD Anderson Cancer Center, Houston, TX
Background: The distinction between plasma cell myeloma (PCM) and lymphoplasmacytic lymphoma (LPL) may sometimes be challenging, particularly in post-therapy settings when the plasma cells (PCs) are the predominant or only residual component in LPL. Comparative studies of the immunophenotypic profiles of PCs in LPL versus PCM are rare. We compared the immunophenotypic profiles of PCs in LPL and CD45 positive PCM patients as assessed by multi-color flow cytometry (FC) to identify features that may facilitate their distinction.
Design: We included 13 cases of consecutively diagnosed LPL and 15 cases of CD45 positive PCM analyzed between June 2011 and October 2011. A 7-color FC assay was performed on bone marrow aspirate material using a panel of monoclonal antibodies against CD45, CD38, CD138, CD19, CD20, CD28, CD56, CD117, cytoplasmic immunoglobulin κ and λ. Marker expression was assessed using a 20% cutoff above the internal control. The intensity of CD45 expression was scored as weak, moderate and bright using expression level on lymphocytes as a control (bright). The monotypic PCs in all PCM cases included in the study had at least a moderate level of CD45 expression.
Results: Serum M protein was of IgM type in all LPL cases and non-IgM type in PCM cases. Each LPL case had an identical light chain expression pattern between the monotypic PCs and monotypic B-cells. Among the LPL group, CD45 expression on the monotypic PCs was negative in 1 case and moderate in 12 cases. Ten cases (77%) showed weak to moderate CD19 expression while 9 cases (69%) showed partial CD20 expression. CD28, CD56, and CD117 were negative in all 13 cases of LPL. Among the myeloma group, moderate CD45 expression was detected in 13 cases (77%) and bright expression of CD45 in 2 cases (13%). CD19 expression was also identified in 2 cases, one weak and the other moderate. Expression was seen for CD20 (partial) in 3 cases (20%), CD28 in 7 (47%), CD56 in 8 (53%), and CD117 in 8 (53%).
Conclusions: The expression intensity of CD45 on monotypic PCs overlaps between LPL versus PCM in this study group. However, other features of IgM-type LPL, including the absence of CD28, CD56, and CD117 expression, and frequent coexpression of CD19 and CD45, are useful findings in delineating LPL from PCM.
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 228, Wednesday Afternoon