A 14-year-old boy presents with severe knee pain and fever. Radiograph shows aggressive periosteal reaction in the proximal tibia described as an 'onion-skin' laminated pattern with a large soft-tissue mass. The metaphysis and diaphysis are involved. Which diagnosis is most consistent?
- A Ewing sarcoma ✓
- B Osteosarcoma
- C Osteomyelitis
- D Chondrosarcoma
Explanation
Ewing sarcoma classically affects the diaphysis and metadiaphysis of long bones in children and adolescents, producing a permeative lytic lesion with a layered 'onion-skin' periosteal reaction and a large soft-tissue mass that is often disproportionately large relative to the bony destruction. Osteosarcoma produces sunburst periosteal reaction with Codman triangle and predominantly involves the metaphysis. Osteomyelitis can mimic this appearance but usually lacks the soft-tissue mass of this magnitude. Chondrosarcoma is rare in this age group and shows chondroid matrix calcification.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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