A second abnormality representing duplication of the reciprocal RUNX1-ETV6 fusion gene was a secondary event, which we hypothesize arose through mitotic recombination errors.     ///    Abnormalities of the der(12)t(12;21) in ETV6-RUNX1 acute lymphoblastic leukemia..     ///     ETV6-RUNX1 fusion [t(12;21)(p13;q22)] occurs in 25% of childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) and is associated with a favorable outcome.     ///    "In conclusion, this study has defined novel abnormalities in ETV6-RUNX1 BCP-ALL, which implicate new genes involved in leukemogenesis.. "    ///    Both abnormalities affect the reciprocal RUNX1-ETV6 fusion product which could either eliminate or amplify its expression and thus contribute to leukemogenesis. 