Mesenchymal chondrosarcoma arising in fibrous dysplasia of the femur.

The occurrence of mesenchymal chondrosarcoma in an area of fibrous dysplasia in the upper femur of a 28 year old man is reported. It is believed that this is the first documented example of such an association. A further unusual feature is the presence of benign giant cells in the mesenchymal chondrosarcomatous component.