Synchronous multifocal osteosarcoma: report of one case.

Synchronous multifocal osteosarcoma (SMOS), defined as more than one bone lesion at presentation, is a rare variant form of osteosarcoma. The onset is usually in childhood or early adolescence without pulmonary metastasis. The prognosis has been dismal. Whether SMOS represents a true multicentic origin or merely bone-to-bone metastases remains controversial. Here, we report a case of SMOS in a 10-year-old girl, with the dominant primary sclerotic tumor arising from the right distal femur. Despite aggressive chemotherapy and limb salvage surgery, she died of progressive multiple axial skeletal and symmetrical metaphyseal long bone diseases within one year after diagnosis. No pulmonary metastasis was found before she died.