RUNX1 rearrangements are well-known driver events, which were first identified in core-binding factor leukaemia (RUNX1-RUNX1T1) and are present in a variety of myeloid and lymphoid malignancies, which are represented by RUNX1-MECOM in CML-BC, ETV6-RUNX1 in B-precursor acute lymphoblastic leukaemia, and other fusions with unknown partners42. Here, MECOM is linked to breast cancer.