When and where do pediatric primary tumors of bone occur?
Ewing sarcoma and osteosarcoma are the most common primary pediatric bone tumors and typically occur between ages 10 to 25 years. The most common sites are the pelvis, thigh, lower leg, upper arm, and ribs, but soft tissue may also be the primary site of involvement. Ewing sarcoma typically does not have a matrix and appears as a permeative aggressive lesion, often with associated periosteal reaction. Most osteosarcomas occur in the metaphysis, typically around the knee. Although the appearance of osteosarcomas is variable, they often produce a characteristic fluffy osteoid matrix.