Uterine leiomyosarcoma metastatic to thyroid shown by 18 F-FDG PET/CT imaging.

About one third of focal thyroid uptakes in a fluorodeoxyglucose (FDG) positron emission tomography/computerized tomography (PET/CT) study are malignant, the most frequent histological type being papillary carcinoma. Metastases to the thyroid account for approximately 7.5% of thyroid malignancies and come mainly from kidney, lung, head and neck, and breast cancers. We report the case of a 64-year-old woman presenting a fast growing thyroid nodule whose primitive or metastatic origin was not obvious, for which 18 F-FDG PET/CT helped in the diagnostic process and in the later management of the patient. Histopathologic findings finally revealed a metastasis of uterine leiomyosarcoma.