An aggressive metaphyseal lesion with osteoid matrix and sunburst periosteal reaction (osteosarcoma) or a permeative diaphyseal lesion with a large soft-tissue mass (Ewing): the radiograph suggests it, whole-bone MRI stages the marrow extent and skip lesions before biopsy.
Orient first
- Osteosarcoma: 10–25 years, around the knee, cloud-like osteoid matrix, Codman triangle.
- Ewing sarcoma: 5–20 years, diaphysis or flat bones, permeative lysis, onion-skin periosteal reaction, soft-tissue mass larger than the bone destruction.
- Biopsy is planned with the treating surgeon — the tract must be excised at surgery.
Acquire the study
- AP and lateral radiographs of the whole bone.
The manoeuvre
- Location on the radiograph: metaphysis vs diaphysis; zone of transition (wide = aggressive).
- Matrix: cloud-like osteoid vs none.
- Periosteal reaction: sunburst, Codman triangle, onion-skin.
- Soft-tissue mass size in cm on the radiograph.
What confirms it
- Histology.
What licenses you to exclude it
- A non-aggressive pattern (narrow zone of transition, solid periosteal reaction) makes a primary bone sarcoma unlikely.
The classic misread
- Osteomyelitis can look identical in a child — biopsy and culture.