Osteosarcoma of the Mandible Arising in Fibrous Dysplasia-A Case Report.

Fibrous dysplasia (FD) is a benign fibro-osseous lesion that typically behaves as a painless, slowly expanding tumor. On rare occasion, FD will undergo malignant transformation. When sarcomatous change occurs, osteosarcoma is the typical variant, followed by chondrosarcoma and fibrosarcoma. The incidence of malignant change varies from 1 to 4% depending on whether the disease is mono-ostotic or polyostotic and syndromic (McCune-Albright or Jaffe-Lichtenstein syndrome). Despite the low incidence of malignant change, the potential lethality of this disease behooves treating surgeons to be keenly aware of the signs and symptoms indicative of malignancy. This report documents a case of spontaneous transformation of FD into osteosarcoma in the setting of longstanding craniomaxillofacial FD in a 39-year-old woman.