Confirmation of light-chain restriction in samples with an excess of phenotypically neoplastic plasma cells.

This figure shows representative plots from 3 patients. (A) A patient with myeloma at presentation, with only neoplastic phenotype (CD19⁻CD56⁺) plasma cells detectable. (B) A MGUS patient with more than 80% of CD45⁻ plasma cells having a neoplastic phenotype (CD19⁻CD56⁺). (C) A MGUS patient with a small population of phenotypically neoplastic plasma cells (in this case, approximately 20% of total plasma cells). For both patients (A) and (B), there is clear cytoplasmic light-chain restriction in the CD45⁻ plasma cell population. For patient B, the CD45⁺ plasma cell population is polyclonal. For patient (C), the neoplastic clone is at a low level, and both CD45⁺ and CD45⁻ are polyclonal, although there is a slight lambda preponderance within the CD45⁻population. MGUS patients were considered suitable for comparison of neoplastic and normal plasma cell CD126 expression if their phenotypic profile was similar to that of patient (B), whereas MGUS patients with a phenotypic profile similar to that of patient (C) were excluded from further analysis.