ES is defined by a chromosomal translocation involving the EWS gene on chromosome 22 with a gene of the ETS family located on different chromosomes [2], leading in 85% of cases to the EWS-FLI1 translocation t(11;22)(q24;q12), whereas the EWS-ERG gene occurs in the majority of the remaining 15% of EFTs. This evidence concerns the gene EWSR1 and Ewing sarcoma.