Primary Extragnathic Osteosarcoma with Visual Loss in an Adolescent Female

The majority of primary osteosarcoma cases affect the metaphyseal plates of long bones, while approximately 5%–10% cases involve the craniofacial bones and are mainly located in the maxilla and mandible. Primary osteosarcoma of the cranial vault is uncommon, and it usually occurs as a metastatic focus from primary diseases elsewhere in older patients. An 18-year-old female presented to our hospital with a 6-month history of a left-sided skull mass involving the forehead and part of the left orbit and 3 months of left visual loss. Clinical examination revealed a 32 × 26 cm firm to soft mass involving the left frontal, parietal and temporal bones, and part of the left orbit. She had no other contributory complaints or significant medical history. A clinical diagnosis of orbital malignancy was made with differential of metastatic left-sided skull tumor. A computed tomography scan revealed a sclerotic lesion arising from the left parietal–temporal bones with sunburst appearances, while fine needle aspiration cytology of the mass showed loose clusters and singles of malignant spindle cells. Incisional biopsy of the mass was diagnosed as fibroblastic variant of osteosarcoma. Extragnathic primary osteosarcoma is uncommon and accounts for less than 1% of craniofacial osteosarcoma. In general, osteosarcoma has a bimodal age of occurrence in adolescents and adults >65 years, and the preferential sites of involvement are the femur, tibia, humerus, and gnathic bones in decreasing frequencies. Our patient is within the first age group; however, the site is unusual and is often associated with secondary osteosarcoma in adults >65 years.