The two most common *malignant* bone tumors in children are
1. Osteosarcoma--Mostly found in the long bones around the knee joint (distal femur>proximal tibia). Presents with pain and swelling. Makes Codman's triangle on x-ray as it lifts up the periosteum. Periosteal osteosarcomas are associated with the "sunburst" finding on xray. Treat with chemo to shrink the tumor and any (micro)metastases, then perform wide, excisional, limb-sparing surgery, followed by more chemo. [Image: Case courtesy of Dr Aditya Shetty, https://radiopaedia.org/cases/27260] and 2. Ewing's sarcoma--Arises in large bones (femur, humerus, pelvis) with pain and swelling. The lesions are lytic, with reactive subperiosteal bone underneath, creating an "onion-skin" effect on xray. MRI is actually better for characterizing any associated soft-tissue changes. Treat with a multi-modal approach of chemo, surgery, and radiation. [Image: Case courtesy of Assoc Prof Frank Gaillard, https://radiopaedia.org/cases/7844]
