Ewing sarcoma is the second most common malignant bone tumor occurring in children and young adults, and accounts for 10-15% of all primary bone tumors. The annual incidence is approximately 0.6/million total population, and it usually occurs between the ages of 10 and 20 years. Ewing's sarcoma is in 85% of cases associated with the translocation t(11;22)(q24;q12), which leads to the formation of the EWSR1-FLI1 fusion gene. In another 10-15% of cases the translocation t(21;22)(q22;q12) generates the EWSR1-ERG fusion, whereas the remaining 1-5% of cases may harbor one of several possible translocations, each resulting in a fusion gene containing a portion of the EWSR1 gene and a member of the ETS family of transcription factors.
