A 12-year-old boy presents with shoulder pain. X-ray shows a well-defined lytic lesion in the epiphysis of the proximal humerus with a thin sclerotic rim and punctate calcifications. There is surrounding oedema on MRI. Which is the MOST likely diagnosis?

• A Giant cell tumor
• B Osteoid osteoma
• C Osteosarcoma
• D Chondroblastoma ✓

Explanation

Chondroblastoma is a benign tumor occurring almost exclusively in the epiphysis of skeletally immature patients (second decade), commonly proximal humerus, distal femur, or proximal tibia. Characteristic punctate 'chicken-wire' calcifications on X-ray are typical. GCT occurs after skeletal maturity. Osteosarcoma is metaphyseal and aggressive, not epiphyseal with calcifications. Osteoid osteoma is intracortical, not epiphyseal.

Reference: Campbell's Operative Orthopaedics, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.