Ewing Sarcoma

Basics

Description

  • Family of cancers with common biology and treatment:
    • Ewing sarcoma of bone
    • Extraskeletal Ewing sarcoma (arises in soft tissue adjacent to bone)
    • Peripheral neuroectodermal tumor (PNET) of bone or soft tissue
    • Askin tumor (Ewing sarcoma of the chest wall)
  • Most common primary tumor sites are as follows:
    • Pelvic bones (26%)
    • Femur (20%)
    • Chest wall (16%)

Epidemiology

  • Second most common primary bone cancer of children and young adults after osteosarcoma
  • Median age of diagnosis is 15 years, although can occur in any age group
  • Slight male predominance

Incidence

  • ~200 to 250 new cases are diagnosed in the United States each year.
  • Annual incidence in the United States of 2.7 cases per million children <15 years of age
  • Most (~65%) occur in the 2nd decade of life.
  • Striking racial difference in incidence: much lower incidence in African American and Asian populations compared to Caucasian population

Risk Factors

  • Most cases occur sporadically.
  • Not associated with familial cancer syndromes
  • Only rarely reported as a second malignancy
  • One genome-wide association study identified several single nucleotide polymorphisms (SNPs) associated with higher risk.
  • Epidemiologic studies suggest higher risk in patients with history of inguinal or umbilical hernia.

General Prevention

There are no known preventive measures.

Pathophysiology

  • Rearrangement of the EWSR1 gene on chromosome 22 is detected in >95% of cases.
    • 85% of cases have a t(11;22) translocation resulting in a fusion EWS-FLI1 protein.
    • 10% of cases have a t(21;22) translocation between EWSR1 and ERG.
    • Other translocation partners occur in <1% of cases and include other members of the ETS transcription factor family, such as ETV1.
  • Fusion proteins thought to play a role as aberrant transcription factor

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