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Introduction: Myeloperoxidase (MPO) is considered a specific marker of myeloid/non‐monocytic lineage in the diagnosis of mixed phenotype acute leukemia (MPAL). However, the clinical significance of isolated dim MPO expression in otherwise typical B lymphoblastic leukemia (B‐ALL; referred to as B/myeloid MPALisoMPO) in adult patients is unknown. Methods: We compared flow cytometric immunophenotype and clinicopathological findings among cases of B/myeloid MPALisoMPO (n = 13), other MPAL subtypes (n = 10, B/myeloid and T/myeloid MPAL), B‐ALL (n = 64), and acute myeloid leukemia (AML, n = 58), using the 2016 WHO classification. For MPAL cases, MPO was reported as the percent of MPO positive blasts and its intensity (dim or moderate/strong). The pattern of heterogenous antigen expression (inversely coordinated expression between myeloid and lymphoid markers and cell size) was assessed. Results: Cases of B/myeloid MPALisoMPO showed a fairly homogenous single B‐lineage blast population with dim MPO expression whereas cases of other MPAL subtypes displayed heterogeneous antigen expression and moderate/strong MPO expression. The percent of MPO positive blasts in these two groups was similar. Expressions of CD15, CD117, and monocytic markers were more common in other MPAL than in B/myeloid MPALisoMPO. B/myeloid MPALisoMPO patients had similar overall and leukemia free survivals as B‐ALL patients and better than other MPAL patients. Conclusion: This is the first study to investigate the clinical significance of adult B/myeloid MPALisoMPO using the 2016 WHO classification. Our results suggest that B/myeloid MPALisoMPO clinically behaves more similarly to B‐ALL than to other MPAL subtypes, supporting the 2016 WHO classification to segregate this entity from other MPAL subtypes. [ABSTRACT FROM AUTHOR]

Objectives: CD25 expression is associated with t(9;22)(q34;q11)/Philadelphia chromosome translocation (Ph); BCR-ABL1 rearrangement in B lymphoblastic leukemia/lymphoma (B-LL). However, the significance of CD25 expression in Ph negative (Ph-) B-LL regarding residual disease (RD) and genetic abnormalities is largely unknown.Methods: CD25 expression by flow cytometry (FC) was correlated with Ph status in 95 newly diagnosed B-LL patients and with RD status in day 29 marrow measured by FC in the context of cytogenetic risk stratification in Ph- patients.Results: CD25 expression was greater in Ph positive (Ph+) patients (80%) than in Ph- patients (17%), predicting Ph+ with 80% sensitivity and 86% specificity. In Ph- patients, CD25 expression (in 14 patients, 16%) was associated with RD in the cytogenetic intermediate-risk group: detectable RD in 50% of CD25+ patients vs 14% of CD25- patients. Interestingly, one CD25+/Ph- patient had a Ph-like genotype ( ZC3HAV1-ABL2 rearrangement), and another had dual MYC-IGH and BCL2-IGH rearrangements.Conclusions: Our findings not only confirm the predictive power of CD25 expression for Ph+ but also demonstrate that CD25 expression is associated with RD (a biomarker correlated with prognosis) in Ph- patients. The latter finding is likely associated with underlying molecular abnormalities, including Ph-like genotype. [ABSTRACT FROM AUTHOR]

Objectives: CD25 expression is associated with t(9;22)(q34;q11)/Philadelphia chromosome translocation (Ph);BCR-ABL1 rearrangement in B lymphoblastic leukemia/ lymphoma (B-LL). However, the significance of CD25 expression in Ph negative (Ph-) B-LL regarding residual disease (RD) and genetic abnormalities is largely unknown. Methods: CD25 expression by flow cytometry (FC) was correlated with Ph status in 95 newly diagnosed B-LL patients and with RD status in day 29 marrow measured by FC in the context of cytogenetic risk stratification in Ph- patients. Results: CD25 expression was greater in Ph positive (Ph+) patients (80%) than in Ph- patients (17%), predicting Ph+ with 80% sensitivity and 86% specificity. In Ph- patients, CD25 expression (in 14 patients, 16%) was associated with RD in the cytogenetic intermediate-risk group: detectable RD in 50% of CD25+ patients vs 14% of CD25- patients. Interestingly, one CD25+/Ph- patient had a Ph-like genotype (ZC3HAV1-ABL2 rearrangement), and another had dual MYC-IGH and BCL2-IGH rearrangements. Conclusions: Our findings not only confirm the predictive power of CD25 expression for Ph+ but also demonstrate that CD25 expression is associated with RD (a biomarker correlated with prognosis) in Ph- patients. The latter finding is likely associated with underlying molecular abnormalities, including Ph-like genotype. [ABSTRACT FROM AUTHOR]