Abstract
e19506
Background: The European Myeloma Network has reported that plasma cell (PC) enumeration by flow cytometry (FC) varies depending on quality of aspirate pull and field biopsied. We conducted a prospective study to evaluate PC site variation content in the core biopsy (CB), PC viability (V) and proportion of monoclonal PCs based on immunophenotypic characteristics, anticoagulant use, and aspirate (A) pull sequence in SMM and MM treatment-naïve patients. Methods: Untreated SMM (n=5) and MM (n=5) patients underwent bilateral bone marrow (BM) A and CB. Bilateral first-pull A were anticoagulated with ethylenediaminetetraacetic acid (EDTA). The second-pull A were anticoagulated with heparin. CB were performed after obtaining all A. The first pull A was sent for morphology and FC evaluation, and the second-pull for FC. CB infiltration by PC was assessed by CD138 immunohistochemistry (IHC). Analysis of PC by FC used CD markers: 19, 45, 20, 38, 138, 27, 28, 19, 81, 126, 200 and 117. V was measured by FC using 7-amino-actinomycin D exclusion. We used the two-tailed Wilcoxon signed rank test to determine the significance of the difference between paired values. Results: The mean difference in estimated percentage of PC infiltration between the right and left CB was 0.033 +/- 0.017 (p=0.25). Phenotypic analysis of PCs by FC showed similar expression of CD markers. PC V was significantly lower in samples anticoagulated with EDTA when compared to heparin (p<0.005), suggesting that the latter is superior for PC analysis. Of importance, the fraction of abnormal PCs determined by FC did not differ significantly between the two sides, use of EDTA/heparin or order of A pull (p>0.05). Conclusions: Based on IHC and FC, our results suggest that in untreated patients with SMM or MM there are no major differences in the estimated number or immunophenotypic characteristics and distribution of PC in marrow samples obtained from two distant bone sites. These observations have implications for current diagnostic and treatment of MM and its precursor disease. More advanced molecular profiling may find biological variation in bone marrow tumor PC extracted from different locations.