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The letter published in Clinical Chemistry & Laboratory Medicine discusses a simple flow cytometry method using a myeloma panel to identify clonal proliferation of mature B-cells in patients initially diagnosed with plasma cell myeloma. Two cases of mature B-cell lymphoma with plasmacytic differentiation were presented, highlighting the importance of evaluating monoclonality of mature B-cells using anti-IgL-κ and IgL-λ antibodies. The study emphasizes the need to consider mature B-cell malignancy in cases of plasma cell proliferation, especially when CD19-positive/CD56-negative plasma cells are detected in flow cytometry analysis. [Extracted from the article]

Persistence of leukemic stem cells (LSCs) results in the recurrence of chronic myeloid leukemia (CML) after the administration of tyrosine kinase inhibitors (TKIs). Thus, the detection of minimal residual disease (MRD) with LSC potential can improve prognosis. Here, we analyzed 115 CML patients and found that CD25 was preferentially expressed on the phenotypic stem and progenitor cells (SPCs), and TKI therapy decreased the number of CD25-positive cells in the SPC fraction. To detect MRD harboring BCR-ABL1 fusion DNA, we developed a highly-sensitive method using patient-specific primers and next-generation sequencing. By using this method, we identified that in patients who achieved molecular remission, almost all residual CD25-positive SPCs were BCR-ABL1-negative. Moreover, in some patients BCR-ABL1 was detectable in peripheral B cells but not in SPCs. We conclude that CD25 marks LSCs at diagnosis but does not mark MRD following TKI treatment and that analysis of peripheral B cells can allow sensitive detection of MRD. [ABSTRACT FROM AUTHOR]