Abstract
In this paper, a rare case of osteosarcoma arising in polyostotic fibrous dysplasia (p. f. d.) is reported. The patient was 30 year-old woman who had been diagnosed to be a p. f. d. at 10 years old. The fibrous dysplasia of the left mandible became malignant, resulting in an osteosarcoma. The patient was operated surgically and, moreover, administered a highdose Methotrexate with citrovorum factor rescue in combination of other chemotherapeutics. There has been no recurrence more than two years and five months after the treatment.
1) In the histology, osteosarcoma is the most frequent neoplasm (58.1%), followed by fibrosarcoma (25.6%), chondrosarcoma (12.8%) and others (3.5%).
2) From the standpoint of the clinical classification of fibrous dysplasia, p. f. d. tends to become malignant more frequently than that monostotic fibrous dysplasia (m. f. d.) does. There are some differences between m. f. d. and p. f. d., in consideration of the histology after malignant transformation, age, sex, anamnesis of radiation therapy, change of Al-Pase value and prognosis.
3) The jaws seem particularly to be frequent sites of malignant change.
