Extensive Intravenous Tumor Thrombus and Right Atrial Bland Thrombus From Poorly Differentiated Thyroid Cancer: 18 F-FDG PET/CT Imaging Findings.

Based on anatomic imaging, 18 F-FDG PET/CT may provide complementary information for distinguishing tumor thrombus from bland thrombus. Although a few cases of 18 F-FDG uptake along the superior vena cava (SVC) in SVC syndrome have been reported, PET/CT findings of 18 F-FDG uptake extending from the SVC into the right brachiocephalic vein, right subclavian vein, and up to the right internal jugular vein, accompanied by right atrial thrombus, to our knowledge, appear rarely documented. Herein, we report a 67-year-old woman with extensive malignant thrombus extending from the right internal jugular vein into the superior vena cava and right atrial thrombus due to poorly differentiated thyroid carcinoma (PDTC) on 18 F-FDG PET/CT.