Cytogenomic Abnormalities in Children With Acute Lymphoblastic Leukemia From Western Mexico: A Single‐Center Fluorescence In Situ Hybridization‐Based Study

ABSTRACT Introduction In Mexico, the 5‐year overall survival (OS) rate for pediatric acute lymphoblastic leukemia (ALL) ranges from 45% to 85%, markedly lower than the ∼90% reported in high‐income countries, where cytogenomic testing is essential for accurate risk stratification and therapeutic decision‐making. The few available data for Mexican cohorts derive from studies conducted in Mexico City using conventional karyotyping, DNA index analysis, and RT‐PCR targeting only four gene fusions. Broader cytogenomic characterization is needed to identify additional prognostic alterations. Methods We analyzed 170 pediatric ALL cases (150 B‐Cell lineage, 10 T‐Cell lineage, and 10 mixed phenotype) using fluorescence in situ hybridization (FISH) with a panel of 11 probe sets targeting recurrent cytogenomic abnormalities. All patients were treated according to the Total XV protocol. Results Among 150 B‐Cell ALL cases, recurrent cytogenomic abnormalities included ETV6 ::RUNX1 ( n = 19), TCF3::PBX1 ( n = 7), BCR::ABL1 ( n = 5), KMT2A ::V ( n = 10), IGH ::V ( n = 7), V:: CRLF2 ( n = 11), iAMP21 ( n = 8), and deletions involving CDKN2A/B ( n = 38), TP53 ( n = 7), RB1 (8), ATM ( n = 1), and ETV6 ( n = 15). Hypodiploidy ( n = 2), high‐hyperdiploidy ( n = 38), low‐hyperdiploidy ( n = 16), and 1q gain ( n = 14) were also identified. Conclusions Our findings reveal a cytogenomic landscape characterized by a predominance of high‐risk abnormalities such as iAMP21 and KMT2A ::V, together with a lower frequency of low‐risk alterations like ETV6::RUNX1 . The frequent coexistence of secondary abnormalities further supports the relevance of comprehensive cytogenomic profiling for accurate risk assessment. The high diagnostic coverage and rapid turnaround of the FISH‐based approach underscore its value as a reliable and efficient diagnostic tool in newly diagnosed ALL. Trial Registration The authors have confirmed clinical trial registration is not needed for this submission