RUNX1 and myelodysplastic syndrome: Approximately 30% of MDS/MPN patients harbor somatic loss-of-function mutations in a transcription factor gene, including RUNX1, GATA2, CUX1, ETV6 and, less frequently (<3%), NPM1, CEBPA and WT1. As a somatic event, they can be present either in the ancestral clone or in subclonal populations and probably constitute driver events that occur after founder mutations in epigenetic regulators and splicing factors [4].