BACKGROUND Flow cytometry is widely used for minimal residual disease (MRD) detection in plasma cell myeloma (PCM). Recently, an increasing number of studies have demonstrated that polytypic plasma cells (PPCs) display greater immunophenotypic variation than previously appreciated. Our aim was to further characterize the immunophenotype of PPC in this setting. METHODS PPC in 102 bone marrow specimens (93 MRD-negative post-treatment PCM and 9 negative initial evaluations for plasma cell neoplasm) were evaluated by 10-color flow cytometry. Frequency of CD19, CD27, CD28, CD56, CD117, and CD138 expression was assessed. RESULTS All cases showed CD27 and CD19 positivity. CD117 was uniformly negative. Percentage of CD138 expression was variable with one negative case (<20% expression). Percentage of CD28 and CD56 expression was variable and included 11 CD28+ cases as well as 38 CD56+ cases. Forty-two percent (43 of 102) cases showed atypical expression of at least one marker with 36 cases (35%) showing atypical expression of a single marker and 7 cases (7%) showing dual atypical marker expression (CD56+/CD28+). CONCLUSIONS Considerable immunophenotypic variation exists in PPC. The assessment of cytoplasmic light chain distribution, in conjunction with surface marker expression, is recommended to avoid diagnostic inaccuracy in MRD evaluation. © 2019 International Clinical Cytometry Society.

中文翻译：

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多参数浆细胞的免疫表型异质性和对多发性流式细胞术检测骨髓瘤最小残留疾病的影响。

背景技术流式细胞术被广泛用于浆细胞骨髓瘤（PCM）中的最小残留疾病（MRD）检测。最近，越来越多的研究表明，多型浆细胞（PPC）显示出比以前认可的更大的免疫表型变异。我们的目的是进一步表征这种情况下PPC的免疫表型。方法采用10色流式细胞仪评估102份骨髓标本中的PPC（93例MRD阴性的治疗后PCM和9例阴性的浆细胞瘤初始评估）。评估了CD19，CD27，CD28，CD56，CD117和CD138表达的频率。结果所有病例均显示CD27和CD19阳性。CD117一律为阴性。在一个阴性病例中，CD138表达的百分比是可变的（<20％表达）。CD28和CD56表达的百分比是可变的，包括11个CD28 +病例以及38个CD56 +病例。42％（102个样本中的43个）病例显示至少一种标记物的非典型表达，其中36个病例（35％）显示单个标记物的非典型表达，而7个病例（7％）显示双重标记物（CD56 + / CD28 +）。结论PPC中存在明显的免疫表型变异。建议结合表面标志物表达评估细胞质轻链分布，以避免MRD评估中的诊断准确性。©2019国际临床细胞计量学会。42％（102个样本中的43个）病例显示至少一种标记物的非典型表达，其中36个病例（35％）显示单个标记物的非典型表达，而7个病例（7％）显示双重标记物（CD56 + / CD28 +）。结论PPC中存在明显的免疫表型变异。建议结合表面标志物表达评估细胞质轻链分布，以避免MRD评估中的诊断准确性。©2019国际临床细胞计量学会。42％（102个样本中的43个）病例显示至少一种标记物的非典型表达，其中36个病例（35％）显示单个标记物的非典型表达，而7个病例（7％）显示双重标记物（CD56 + / CD28 +）。结论PPC中存在明显的免疫表型变异。建议结合表面标志物表达评估细胞质轻链分布，以避免MRD评估中的诊断准确性。©2019国际临床细胞计量学会。