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:
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.
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)
Lamellated (“onion skin”) periosteal reaction in Ewing’s sarcoma
Next step: is to know the type of bone matrix