Bone tumour made easy Part I

Differentiating different bone tumours is a dauting task. But fortunately we only need to know which is aggressive (which needs to be biopsied) and which is non-aggressive (dont touch lesion).

I’ve divided this into 2 sections. This is part I

This is the mnemonic that I come out with when evaluating a bone tumour: CAP

  • Cortical destruction
  • Area of transition
  • Periosteal reaction


Area of transition simplified:


Periosteal reaction simplified

Non-aggressive periosteal reaction:

  • The lesion grows slowly so there is time for the bone to re-ossify itself.
  • Non aggressive periosteal reaction looks like a healing callus.

Smooth and continuous periosteal reaction in osteoid osteoma

Aggressive periosteal reaction: The lesion grows so fast until

  • Ossification could not happen (unossified periosteum is radiolucent)
  • Ossification happens irregularly (spiculated, sunburst appearance)
  • Ossification only partially (Codman’s triangle)
  • Multiple layers of ossification (following the multiple layers of periosteal reactions) (lamellated appearance)

download  sunburst-ewings
Spiculated periosteal reaction (left: hair on end; right: sunburst)

Codman’s triangle

Lamellated (“onion skin”) periosteal reaction in Ewing’s sarcoma

Next step: is to know the type of bone matrix



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