EWSR1 and Ewing sarcoma: A specific chromosomal translocation t(11;22) (q24;q12) occurs in ES (Delattre et al., 1992), and this chromosomal translocation results in the generation of a chimeric EWS-FLI1 fusion protein, created by the fusion of the amino-terminal portion of the FET family gene EWSR1 with the carboxyl-terminal DNA-binding domain of the ETS family gene, FLI1. Approximately 80–90% of patients with ES harbor the EWS-FLI1 fusion protein.