The most common sites of involvement are medullary cavity of long tubular bones (femur, tibia, humerus, fibula), flat bones of pelvis, vertebra, ribs, and clavicle. Radiographs show a destructive lesion with widening of medullary cavity. Reactive periosteal bone deposits perpendicular to the cortex (sun-ray appearance) are present mid-shaft in this image. When deposited in a concentric fashion, it creates an onion-skin appearance.
return to Ewing Sarcoma/PNET