Advances in Diagnosis and Classification of B-ALL: Comparative Insights from Updated Guidelines

Accurate molecular classification is essential for diagnosis, risk stratification, and treatment selection in B-cell lymphoblastic leukemia (B-ALL). In this study, we performed a comprehensive real-world reclassification of 1,015 consecutively diagnosed B-ALL cases using the 5th edition of the WHO classification (WHO-HAEM5) and the International Consensus Classification (ICC). An integrative genomic strategy-combining whole transcriptome sequencing (WTS), fusion detection, mutational analysis, and cytogenetics-enabled reclassification according to both WHO-HAEM5 and ICC frameworks, substantially reducing the proportion of unclassifiable B-ALL from 41.9% (WHO-HAEM4R) to 15.9% (WHO-HAEM5) and 11.9% (ICC). Distinct clinical and prognostic features were identified across newly defined subtypes. Multivariable analysis confirmed this genomic classification as a robust independent predictor of survival, after adjusting for age, minimal residual disease status, and transplant intervention. Specifically, HLF-rearranged and MEF2D-rearranged B-ALL conferred a persistently poor prognosis across all age groups despite allogeneic hematopoietic stem cell transplantation, highlighting an urgent need for novel therapeutic strategies. Gene expression profiling resolved cryptic subtypes including ETV6::RUNX1-like, ZNF384-rearranged-like, and BCR::ABL1-like B-ALL, and uncovered diagnostic ambiguity in cases with concurrent lesions. Additionally, we report emerging high-risk groups-including IDH1/2- and ZEB2 Q1072-mutated B-ALL-that may warrant recognition as distinct molecular entities. Our findings demonstrate the clinical utility of integrative transcriptomic profiling in refining B-ALL taxonomy, guiding risk-adapted therapies, and informing future revisions of diagnostic standards. This study supports the incorporation of high-throughput molecular diagnostics into routine leukemia classification and precision treatment planning.