EWSR1 and Ewing sarcoma: Virtually all Ewing sarcoma tumors harbor a somatic translocation, fusing the EWSR1 gene (encoding the EWS protein) on chromosome 22 with a member of the ETS family of transcription factors, most commonly FLI1 (encoding the FLI protein), located on chromosome 11 [t(11;22)(q24;q12)].