Although CDKN2A/B deletions are detected in approximately 20–25% of pediatric B-cell precursor (BCP) ALL cases and 38.5–50% of T-ALL patients [19,20,21], with the percentage rising to more than 80% in cases of B-other and BCR/ABL1-like ALL [22,23], results on the prognostic impact of the biallelic or monoallelic deletion remain inconclusive [24,25,26,27,28,29,30,31,32,33,34]. The gene discussed is ABL1; the disease is acute lymphoblastic leukemia.