Well-differentiated intra-osseous osteosarcoma in the mandible of a six-year-old child.

The case of an osteosarcoma arising in the mandible of a six-year-old child is presented. It was originally misdiagnosed as a desmoplastic fibroma, and after initial curettage continued to grow for twelve years. The differential diagnosis is presented and details of the surgical access and difficulties encountered in the surgical removal of this very large tumour are described. The relationship between pre-existing disease and osteosarcoma of the mandible is discussed, and the difficulties experienced in distinguishing between the fibro-osseous lesions and osteosarcoma of the mandible are highlighted. The case is presented as a well-differentiated, intra-osseous osteosarcoma with subsequent transformation into a high-grade, conventional osteosarcoma.