Low-grade central osteosarcoma, a rare subtype of osteosarcoma, is less aggressive than conventional osteosarcoma. We report ac case of low-grade central osteosarcoma of the mandible. A 52-year-old woman presented to our department for treatment of a swelling in the right side of the mandible. Computed tomography revealed ground glass radiopaque lesions associated with an expansive growth pattern in the mandibular bone. Because a suspicion of low-grade central osteosarcoma was diagnosed In the biopsy sample provided from the previous hospital, the lesion was surgically resected. Histopathologically, the tumor consisted of a dense proliferation of spindle cells with mild atypia. At the periphery of the lesion, the normal cortical bone was invaded by tumor nests. Low-grade central osteosarcoma was diagnosed in the surgical specimen. Tumor recurrence has not been observed for more than 6 years after surgery. Low-grade central osteosarcoma is hard to differentiate from osteogenic benign neoplasm or bone malformation. Therefore, when radiographic findings reveal an expansive ground glass appearance, a bone biopsy including the normal cortical bone and the central part of the lesion is essential.
