Genetically, ES are defined by EWS–ETS translocations encoding aberrant transcription factors presumed to induce the highly malignant phenotype of this disease (Delattre et al., 1994; Lessnick and Ladanyi, 2012; Mackintosh et al., 2010; Sorensen et al., 1994). The gene discussed is EWSR1; the disease is Ewing sarcoma.