Enchondromas are very common lesions and involve mostly the long bones. They are by definition cartilage containing lesions and can usually be observed. They happen in older patients but are likely to be developmental though probably not congenital in origin. Indices of poor prognosis make a diagnostic and therapeutic measure necessary in the form of curettage and cryotherapy if a chondrosarcoma grade I is suspected. Grade II and III chondrosarcomas are usually much more aggressive and do not pose diagnostic dilemmas.
The main criterion for malignancy or aggressive behaviour include
1. Size greater than 3cm
2. Bone expansion
3. Scalloping of walls
4. Myxoid appearance versus the benign icing sugar
5. Activity on bone scan
6. (Often) Pain
Figure. This 55 year-old lady had pain in the knee due to patello-femoral (knee cap) arthritis. The MRI and bone scan showed no activity and the lesion could be observed.However, because she also had a meniscal tear (the actual cause of her pain) she underwent an arthroscopic meniscectomy and biopsy at the same sitting confirming the diagnosis of an enchondroma.