have established that, at the molecular level, fusion of the EWSR1 gene on chromosome 22 with a member of the erythroblast transformation-specific (ETS) family of transcription factors—most commonly FLI1 on chromosome 11(q24) or ERG on chromosome 21(q22), results in the development of an oncogenic transcription factor that gives rise to Ewing sarcoma in its various forms (10, 11). The gene discussed is ERG; the disease is Ewing sarcoma.