EWSR1 and Ewing sarcoma: ES, the second most common pediatric bone cancer, is characterized by a chromosomal translocation that mostly results in the fusion between the EWS breakpoint region 1/EWS RNA binding protein 1 (EWSR1) gene on chromosome 22 and an E26 transformation-specific (ETS) family transcription factor gene, either FLI1 at chromosome 11q24 or ERG at 21q11 [1,2].