Chondrosarcomas are usually located outside the medullary canal of the bony component. When an osteosarcoma is diagnosed, it is usually a dedifferentiation of a preexisting peripheral chondrosarcoma1.
This patient had a previous history of femoral fractures and exostosis. He developed new symptomatic bony pain, raising the possibility of osteosarcoma once seen on x-ray findings. Changes in the marrow of the exostosis and medullary canal of the bone on CT and MR imaging was seen. Associated destruction of the cortex and soft-tissue involvement gave a differential diagnosis of chondrosarcoma 1.
A study found that cases of degeneration of osteochondromas to chondrosarcomas occurred in patients with previous or existing multiple exostoses, and their average age was 34.9 year 2.
Specialist oncology review is needed in this case to determine management and treatment plan.