A Case Report of Metastatic Primary Thyroid Sarcoma Evaluated by 18F-FDG PET/CT.

Among the thyroid malignancies, primary thyroid sarcomas are very rare, comprising < 1% of all thyroid malignancies. Sarcoma, in particular spindle cell sarcomas of the thyroid gland, is very rare and aggressive which carries poor prognosis. Very little has been published regarding imaging findings and metastatic patterns of this rare entity. We report a case of metastatic spindle cell sarcoma of the thyroid presenting with hoarseness of voice and anterior neck swelling. Subsequent fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging demonstrated a fluorine-18-FDG avid mass lesion in the left lobe of the thyroid, along with FDG avid cervical lymph nodes and multiple FDG avid nodules of varying sizes in the bilateral lung fields. 18F-FDG PET/CT proved invaluable in accurately staging this rare case of metastatic high-grade sarcoma originating from the thyroid.