Ewing sarcoma is a malignant tumor from undifferentiated mesenchymal bone cells. It is the second most common primary bone malignancy in children. It generally occurs in the second decade of life (mean age is 11 years). Males are affected twice as often as females. Patients will present with symptoms including pain, swelling, elevated WBC, elevated ESR, and occasionally fever.

Most common bone distribution: femur > pelvis > tibia > humerus > ribs

Radiographic findings include:

• "moth-eaten" appearance
• distribution in the long and flat bones
• lytic lesions with poorly defined margins and permeative pattern (these tumors can appear predominantly sclerotic in 15% of cases)
• "onion skin" periosteum (non-specific)
• large soft-tissue component

Most Ewing tumors are very radiosensitive; radiation therapy is the treatment of choice.

At the time of presentation, approximately one-third of patients will already have metastases to the lung, other bones, or lymph nodes. 5-year survival is 70% for localized disease and 30% for metastatic disease.

Ewing Sarcoma in a 15-year old male with recent onset of pain in the left leg. AP radiograph of the left distal femur demonstrates widening with sclerosis. Note the elevation of the periosteum with laying down of calcification forming an "onion skin" appearance.