DUX4 and Ewing sarcoma: ELS/URCS refers to a kind of “small round cell” sarcoma, with many features of Ewing sarcoma, but lacks rearrangements in the EWSR1 gene, a salient characteristic of Ewing sarcoma.[2,3] ELS/URCS is usually more aggressive than Ewing sarcoma.[4] and has recently been associated with two recurrent oncogenic fusion rearrangements, BCOR-CCNB3 and CIC-DUX4 in the literature.[4–10]