A 16-year-old male presents with progressive pain and swelling in his distal femur for 3 months. X-rays show a destructive lesion in the metaphysis with a 'sunburst' periosteal reaction and Codman's triangle. Which of the following is the most likely diagnosis?

Explanation

The clinical presentation of a rapidly growing painful mass in the metaphysis of a long bone in an adolescent, combined with classic radiographic features like a 'sunburst' periosteal reaction (due to spicules of new bone radiating outwards) and Codman's triangle (elevation of the periosteum by tumor), are highly characteristic of osteosarcoma. Osteochondroma is a benign exostosis. Ewing's sarcoma typically presents with an 'onion-skin' periosteal reaction and often affects the diaphysis. Giant cell tumor is usually epiphyseal and occurs in young adults.