RUNX1 aberrations in ETV6/RUNX1-positive and ETV6/RUNX1-negative patients: its hemato-pathological and prognostic significance in a large cohort (619 cases) of ALL.

A large-cohort study (619) of acute lymphoblastic leukemia (ALL) revealed an ETV6/RUNX1 (previously known as TEL/AML1) incidence of 18% in pediatric B-cell precussor ALL, indicating no geographical heterogeinity. Association of CD34-negative phenotype, peak incidence in the 3- to 7-year age group, and a comparatively low frequency of ETV6 homologue loss in ETV6/RUNX1-positive cases were distinct findings in this series. Additional genetic changes, such as ETV6 loss, extra RUNX1, ETV6/RUNX1 duplication, and MLL aberrations in the ETV6/RUNX1-positive group, supported the hypothesis of the ETV6/RUNX1 leukemogenic model that these secondary changes are necessary for leukemogenesis rather than progression of disease.

Coexistence of ETV6/RUNX1 and MLL aberrations in B-cell precursor acute lymphoblastic leukemia discloses a small subclass of BCP-ALL.

Out of 76 pediatric cases of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) positive for ETV6/RUNX1 (previously TEL/AML1) resulting from t(12;21), 7 cases revealed coexistence of ETV6/RUNX1 and MLL aberrations. One case of der(21) duplication with ETV6/RUNX1 exhibited a novel MLL translocation variant t(6;11)(p21.1p23;q13q25), with translocation of 3' telomeric MLL and deletion of 5' centromeric MLL.