A 15-year-old boy presents with pain and a firm swelling around the knee for 3 months. X-ray shows a dense sunburst pattern of periosteal new bone with soft tissue extension and lifting of the periosteum forming a Codman's triangle. The most likely diagnosis is:
- A Ewing's sarcoma
- B Giant cell tumor of bone
- C Osteosarcoma ✓
- D Chondrosarcoma
Correct answer: C. Osteosarcoma
Explanation
Osteosarcoma (osteogenic sarcoma) is the most common primary malignant bone tumour in adolescents, with a peak incidence in the second decade. It characteristically involves the metaphysis of long bones around the knee — distal femur most often, then proximal tibia. The sunburst pattern reflects tumour bone radiating outward; Codman's triangle is formed by periosteum lifted at the tumour margin. Serum alkaline phosphatase is elevated. Treatment is neoadjuvant chemotherapy followed by limb-salvage surgery.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.