Fibrous dysplasia is a benign condition consisting in replacement of normal bone with fibrous tissue and unorganized bone woven (1). The malignant change to osteosarcoma can appear in less than 1% of cases (2). Osteosarcoma is found most often, but other lesions as fibrosarcoma, chondrosarcoma, and malignant fibrohistiocytoma are reported (3,4).
Fibrous dysplasia appears due to somatic activation of mutation in the G protein encoded by the gene GNAS. GNAS gene mutations cause McCune-Albright syndrome defined by the triad of PFD, café-au-lait skin macules and endocrinopathies, including amongothers, precocious puberty (5). It is caused by a random mutation in the GNAS gene that occurs very early in development.