A 13-year-old boy presents with a large mixed lytic and sclerotic lesion located in the metaphysis of the distal femur. What is the most probable diagnosis?

Explanation

Osteosarcoma is the most common primary malignant bone tumor in adolescents, typically presenting as a mixed lytic and blastic lesion in the metaphyseal region of long bones such as the distal femur. Ewing sarcoma usually affects the diaphysis, chondrosarcoma is more common in adults, and giant cell tumors typically occur in adults and are purely lytic.