EWSR1 and Ewing sarcoma: Decades after the discovery of BCR-ABL1 t(9;22)(q34;q11) in chronic myeloid leukemia [1, 2] and EWSR1-FLI1 t(22;11)(q24;12) in Ewing sarcoma (EwS) [3], more than 20,000 fusion genes have been identified in human malignancies [4].