EWSR1 and leukemia: Fusion oncogenes consisting of FET family genes FUS, EWSR1, TAF15 (Fused in sarcoma, Ewing sarcoma breakpoint region 1, TATA‐box binding protein associated factor 15) as 5’‐partners and alternative transcription factor‐coding genes as 3’‐partners are characteristic of more than 20 types of sarcoma and leukaemia [1], including myxoid liposarcoma (MLS) and Ewing sarcoma (EWS) (hereby also called FET sarcoma; Fig 1A).