Bone Tumors — Osteosarcoma

Which chromosomal abnormality is most commonly associated with osteosarcoma?

Which of the following is the most common site of origin for osteosarcoma in the long bones?

A 16-year-old boy presents with a 3-month history of progressive pain and swelling over the distal femur. He reports the pain is worse at night and does not respond well to NSAIDs. On examination, there is a firm, fixed mass over the distal femoral metaphysis with warmth and overlying skin erythema. Plain radiographs show a mixed lytic and sclerotic lesion with cortical destruction and a sunburst pattern of new bone formation. The lesion extends into the soft tissues with a Codman triangle visible. What is the most likely diagnosis?

A 14-year-old girl with osteosarcoma of the proximal tibia has completed neoadjuvant MAP chemotherapy. Surgical resection shows only 5% viable tumor (>90% necrosis). What is the preferred adjuvant chemotherapy regimen?

A 16-year-old boy presents with progressive pain and swelling around the knee for 3 months. Radiographs show a mixed lytic and sclerotic lesion with cortical destruction and periosteal new bone formation. Histology confirms osteosarcoma. Which is the most common site of origin within the femur in osteosarcoma?