A 59-year-old man admitted to the hospital complained of left arm and neck pain. Magnetic resonance imaging was performed for possible cervical discopathy. It revealed that in the C7 vertebral body, lesions with surrounding bone marrow edema were observed, which were compatible with metastasis that caused cervical stenosis. Cervical stenosis surgery was performed, and the lesion was pathologically diagnosed as a metastasis of thyroid carcinoma. ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) scan was ordered for further evaluation. The PET/CT images showed an increased ¹⁸F-FDG uptake from the left internal jugular vein to the right atrium. It was considered a malignant thrombus.