Ewing sarcoma is a type of pediatric cancer that forms in bone or soft tissue. Symptoms may include swelling and pain at the site of the tumor, fever, and a bone fracture. The most common areas where it begins are the legs, pelvis, and chest wall. In about 25% of cases, the cancer has already spread to other parts of the body at the time of diagnosis. Complications may include a pleural effusion or paraplegia. It is a type of small round cell sarcoma. The cause of Ewing sarcoma is unknown, most cases appearing to occur randomly. Though not strongly associated with known hereditary cancer syndromes, accumulating evidence suggests a strong inherited risk factor, identifying a genetic component having multiple chromosome loci associated with Ewing sarcoma susceptibility. Sometimes Ewing sarcoma is associated with a germline mutation. The underlying mechanism often involves a genetic change known as a reciprocal translocation. Diagnosis is based on biopsy of the tumor. Treatment often includes chemotherapy, radiation therapy, surgery, and stem cell transplant. Targeted therapy and immunotherapy are being studied. Five-year survival is about 70%. A number of factors, however, affect this estimate. In 1920, James Ewing discerned that these tumors are a distinct type of cancer. It affects approximately one in a million people per year in the United States. Ewing sarcoma occurs most often in teenagers and young adults and represents 2% of childhood cancers. Caucasians are affected more often than African Americans or Asians, while males are affected more often than females.

Reference
Wiki: Ewing sarcoma