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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