A 13-year-old boy presents with progressively worsening pain at the knee. Radiograph shows a dense sclerotic lesion in the distal femoral metaphysis with an aggressive periosteal reaction forming a triangular elevation of the periosteum at the tumor margin and radiating spicules perpendicular to the cortex. What is this periosteal reaction called?
- A Onion-skin periosteal reaction with Codman triangle
- B Lamellar periosteal reaction without cortical breach
- C Sunburst periosteal reaction with Codman triangle ✓
- D Eggshell periosteal thinning
Correct answer: C. Sunburst periosteal reaction with Codman triangle
Explanation
Osteosarcoma characteristically produces a sunburst or hair-on-end periosteal reaction with radiating spicules of new bone perpendicular to the cortex, combined with a Codman triangle formed by lifting of the periosteum at the tumor periphery. The Codman triangle alone is not specific to osteosarcoma but the combination with sunburst reaction in a metaphyseal lesion in an adolescent is pathognomonic. The onion-skin pattern is more characteristic of Ewing sarcoma. Eggshell thinning is seen in giant cell tumors and aneurysmal bone cysts.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.