Metastatic undifferentiated spindle cell sarcoma of the thyroid gland evaluated by 18F-FDG PET/CT.

We describe a rare case of metastatic undifferentiated spindle cell sarcoma (USCS) of the thyroid gland evaluated by 18F-FDG PET/CT. A 63-year-old male patient with histological diagnosis of USCS of the thyroid gland underwent 18F-FDG PET/CT for staging. PET/CT revealed increased radiopharmaceutical uptake corresponding to a thyroid mass and mild 18F-FDG uptake in a 7-mm lung nodule, which was diagnosed as USCS metastasis. Based on these findings, the patient was referred to surgery and chemotherapy, but he died 6 months later for disease progression.