Osteosarcoma arising in fibrous dysplasia, confirmed by mutational analysis of GNAS gene

In this case, point mutations of GNAS were found in the FD and osteosarcoma but not in the adjacent normal tissues, suggesting that osteosarcoma was derived from the spindle cells of FD. This is the first report to clearly show that osteosarcoma is derived from the spindle cells in fibrous dysplasia (FD).