Diagnosis: Chromosome Changes in Ewing Sarcoma
• Ewing sarcomas, also known as primitive neuroectodermal tumors (PNET), are highly aggressive tumors of neural crest derivation. The cytogenetic hallmark of Ewing sarcoma is t(11;22)(q24;q12), which is seen in approximately 90% of all histologic subtypes. This translocation is diagnostic of this entity.
• The t(11;22)(q24;q12) translocation results in rearrangement of the EWS gene at 11q24 and the FLI1 gene at 22q12. The translocation results in the formation of the ESW-FLI1 chimeric protein.
• Approximately 5% of Ewing sarcomas result from variant translocations involving the EWS gene at 11q24, resulting in t(21;22)(q12;q12)[EWS-ERG] and t(7;22)(p22;q12) [EWS-ETV1].