The immunophenotypic stability of plasma cell myeloma by flow cytometry

• Published in: International journal of laboratory hematology 2011-10, Vol.33 (5), p.483-491
• Main Authors: SPEARS, M. D., OLTEANU, H., KROFT, S. H., HARRINGTON, A. M.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Bone Marrow Cells - metabolism; Bone Marrow Cells - pathology; CD19 antigen; CD20 antigen; CD38 antigen; CD45 antigen; CD56 antigen; Female; Flow Cytometry; Follow-Up Studies; Humans; immunophenotype; Immunophenotyping; Light chains; Male; Middle Aged; minimal residual disease; Multiple Myeloma - diagnosis; Multiple Myeloma - metabolism; Myeloma; Plasma cell myeloma; Plasma cells; Plasma Cells - metabolism; Plasma Cells - pathology; stability
• ISSN: 1751-5521; 1751-553X
• DOI: 10.1111/j.1751-553X.2011.01317.x

Summary Introduction:  Flow cytometry (FC) has become increasingly utilized in the diagnosis and monitoring of plasma cell myeloma (PCM), though few studies have evaluated the longitudinal stability of antigen expression. Methods:  We studied 45 PCM patients by four‐color FC for shifts in CD19, CD20, CD38, CD45, CD56, and cytoplasmic light chain expression, between diagnostic/first encounter and positive follow‐up analyses. An immunophenotypic (IP) change was defined as gain, loss, or ½ log shift of antigen expression. Results:  An IP change was observed in 14/45 (31%) patients, with single IP changes in 9/14, two changes in 2/14, and three changes in 3/14. 3/14 reverted from an aberrant to a normal plasma cell IP, while remaining light chain‐restricted. Changes in expression of CD45 occurred in 9/45 (20%), CD19 in 5/45 (11.1%), CD20 in 2/45 (4.4%), and CD56 in 5/45 (11.1%). Conclusion:  Approximately 1/3 of PCM cases show IP changes over time, with CD45 the least stable antigen. Recognition of this relative instability is important to avoid narrow targeting of follow‐up FC analyses, especially for minimal residual disease monitoring.