FLT3 Gene Involvement in B-cell Acute Lymphoblastic Leukemia (B-ALL).

Objectives: A recent landmark study reported the value of next-generation sequencing (NGS) to uncover pathogenic abnormalities of clinical significance in patients with pediatric B-ALL enrolled in the UKALL2003 clinical trial (Schwab et al., 2023). NGS, as whole genome sequencing (WGS) or targeted NGS (t-NGS), was combined with previous data (cytogenetics, FISH and MLPA) from 351 pediatric patients with precursor B-ALL who lacked a defining genetic abnormality (B-other ALL). This integration of tests classified patients into 15 distinct subtypes, each one characterized by a specific abnormality. The most frequent subtypes were defined by abnormalities of PAX5, DUX4, ZNF384, an ABL class, and an ETV6::RUNX1-like with a gene expression profile similar to the typical ETV6::RUNX1 but without the specific abnormality. Quite conspicuously, WGS detected some classical abnormalities that remained undetected by standard cytogenomic methods. This application of NGS integrated into standard cytogenomic assays is a decisive advance in classifying patients with B-other ALL into distinct subtypes characterized by unique genomic changes. The addition of NGS improved the identification of pathogenic abnormalities and refined the classification as well as the risk stratification to determine clinical prognosis.