Ewing Sarcoma

Descriptive text is not available for this imageBASICS

DESCRIPTION

  • Cancer of the bone and soft tissue characterized by FET-ETS family translocations:
    • Ewing sarcoma of bone
    • Extraskeletal Ewing sarcoma (arises in soft tissue adjacent to bone)
    • 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 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 European American population

RISK FACTORS

  • Most cases occur sporadically.
  • Not associated with familial cancer syndromes
  • Only rarely reported as a second malignancy
  • Epidemiologic studies suggest higher risk in patients with history of inguinal or umbilical hernia.

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.
    • Translocations that involve FUS rather than EWSR1 also considered molecular evidence of Ewing sarcoma if partnered with a member of the ETS transcription factor family
  • Fusion proteins thought to play a role as an aberrant transcription factor

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