On plain radiograph, an aggressive bone lesion in the proximal tibia metaphysis of a 16-year-old shows the 'Codman's triangle' and sunburst pattern. On MRI, the mass shows heterogeneous signal with an intact cortex in some areas but cortical breakthrough elsewhere. The MOST likely diagnosis is:

• A Osteosarcoma ✓
• B Ewing's sarcoma
• C Giant cell tumour
• D Chondrosarcoma

Explanation

Osteosarcoma classically presents in adolescents at the metaphysis of long bones (distal femur, proximal tibia most common). Radiographic features include Codman's triangle (periosteal reaction) and sunburst/hair-on-end periosteal pattern indicating aggressive behaviour. MRI demonstrates cortical destruction and soft-tissue extension. Ewing's sarcoma shows onion-skin periosteal reaction and is diaphyseal. GCT occurs at the epiphysis in skeletally mature patients. Chondrosarcoma is a tumour of adults.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.