U2AF1 and myeloproliferative neoplasm: ASXL1, TET2, U2AF1, SRSF2 and SF3B1 mutations are frequently detected in MDS/MPN-unclassifiable, further supporting the development of myelodysplastic features in the MF phenotype (with the ensuing cytopenias) when ≥3 non-driver mutations are acquired [58].