Primary Thyroid Osteosarcoma Staging and Evaluation of Response to Therapy With F-18 FDG PET-CT

Extraosseous osteosarcomas account for less than 5% of all osteosarcomas. Primary osteosarcoma of the thyroid is a very rare tumor, with only 28 cases described in the published data. This is a case of a 40-year-old woman, 3 months postpartum, who presented with a rapidly growing mass in the neck, causing airway obstruction. An F-18 FDG PET-CT showed a large intensely FDG-avid mass in the thyroid gland, which was histopathologically confirmed to be a primary thyroid osteosarcoma. The patient was treated with tracheostomy, radiation therapy, and 2 cycles of chemotherapy. A posttherapy F-18 FDG PET-CT scan showed that the thyroid osteosarcoma was responding to therapy; however, the patient had developed new lung metastases.