PAX5 and acute lymphoblastic leukemia: This is especially striking as this is the only ETV6::RUNX1 sample (ER4) where the “second hit” driving leukemogenesis is a partial loss of PAX5 rather than loss of ETV6, supportive of a distinct molecular mechanism that has been observed in this recently described subtype of ETV6::RUNX1 B-ALL (Z. Li et al., 2025).