CD25 expression in B lymphoblastic leukemia/lymphoma predicts t(9;22)(q34;q11)/Philadelphia chromosome translocation (Ph) and is associated with residual disease in Ph-negative patients

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.