• Ewing sarcoma family tumors are small, round cell tumors that arise either in bone or soft tissues (extraosseous). These tumors are often referred to as "Ewing sarcoma's" or "pPNET" (peripheral primitive neuroectodermal tumor). In the past, chest wall pPNET’s were called Askin tumor. The cell of origin for this family of tumors is unknown. 
• Ewing sarcoma family tumors can occur at any site, but most commonly develop in the arms or legs, pelvis or chest wall. These tumors can spread to the lungs, bone and bone marrow. Pain and swelling at the sites of disease are the most common presenting symptoms. Sometimes patients may also have fever. Because these symptoms are suggestive of an infection, a delay in the diagnosis of a malignancy may occur.
• More than 85 percent of Ewing sarcoma family tumors are characterized by a specific translocation between chromosomes 11 and 22. This translocation puts together pieces of two chromosomes (genetic material) that would normally not be together, and fuses two genes, FLI  and EWS, creating what is called a fusion transcript. This translocation is felt to be important in why these tumors develop. In addition, the detection of this translocation in tumor samples has improved our ability to accurately diagnose these tumors.

Incidence

• Ewing sarcoma family tumors are the second most common type of bone cancer in children and adolescence.
• Approximately 200 new cases of this type of tumor are diagnosed in the United States per year.
• Almost 50 percent of patients with Ewing family of tumors are between 10 and 20 years of age.

Influencing Factors

• These tumors are very uncommon in people of African American and Asian descent. 
• Ewing sarcoma family of tumors are not commonly associated with other congenital diseases and there is no convincing evidence that this type of tumor is inherited.
• Although a rare occurrence, Ewing sarcoma family of tumors can occur as a second malignancy, especially in patients who have received radiotherapy.