The t(8;21) involving RUNX1 and RUNXT1, the t(12;21) occurring in pediatric acute lymphoblastic leukemia and generating the ETV6–RUNX1 fusion, and the t(3;21) occurring in therapy-related AML and myelodysplastic syndrome and involving the MECOM oncogene are among those that are the most frequent. This evidence concerns the gene RUNX1 and myelodysplastic syndrome.