On MRI, a bone tumor in the distal femur metaphysis shows low T1 signal, high T2 signal, and marked surrounding soft tissue edema. On T1 post-gadolinium sequence, the tumor shows peripheral nodular enhancement and central non-enhancement. Which diagnosis is MOST likely?

• A Osteosarcoma
• B Giant cell tumor of bone
• C Chondrosarcoma
• D Aneurysmal bone cyst ✓

Explanation

Aneurysmal bone cyst (ABC) classically shows fluid-fluid levels on T2-weighted or gradient-echo MRI — the dependent hemosiderin (low signal) layering beneath the supernatant serum/fluid (high signal). It enhances peripherally at the cyst walls with central non-enhancement. ABCs are expansile lytic lesions of the metaphysis in young patients. Osteosarcoma has aggressive features with Codman triangle and periosteal reaction. Giant cell tumor occurs at the epiphysis after physeal closure. Chondrosarcoma shows lobulated low T1 / high T2 signal with septal/ring enhancement reflecting its cartilaginous matrix.

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

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Written and medically reviewed by the StethoPrep medical team.