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Sunburst (sunray) sign

MSKRadiograph / CT

Fine spiculated new bone radiates outward perpendicular to the cortex like rays of the sun.

What it means

An aggressive periosteal reaction typical of osteosarcoma.

Mechanism

Tumour extending through the cortex stimulates bone formation along Sharpey fibres and perpendicular vessels, producing radiating spicules.

Associated conditions

  • Osteosarcoma
  • Ewing sarcoma
  • Metastases (e.g. prostate)
  • Aggressive haemangioma

Pearls

  • A sunburst pattern is one of the classic aggressive periosteal reactions.
  • It commonly accompanies a Codman triangle in high-grade osteosarcoma.

References

  • Radiopaedia: Sunburst appearance

For educational use only. This dictionary is a study aid and reference, not a diagnostic tool, and must not be used to guide clinical decisions or patient care. Imaging appearances vary; always correlate with the full clinical picture and confirm with a qualified radiologist.