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A 61-year-old Japanese man had dedifferentiated chondrosarcoma (DCS) arising in the right femur. Preoperative contrast-enhanced computed tomography (CT) revealed a contrast defect in the right femoral vein (Figure A ). We suspected that either a benign thrombus or a tumor thrombus had developed involving the inferior vena cava (IVC) and placed a temporary IVC filter (Neuhaus Protect, Toray Medical, Tokyo, Japan) in the perioperative period and he underwent femoral tumor removal. Twenty days after the operation, contrast-enhanced CT showed extension of the contrast defect from the right popliteal vein to IVC and new pulmonary embolic findings in the right pulmonary artery (Figure B, C ). We started him on anticoagulation therapy with rivaroxaban 15 mg/day, which did not reduce the contrast defect or the pulmonary embolism. We placed the IVC Filter (Denali, Bard Peripheral Vascular, Inc., Tempe, AZ) and observed the lesion with angioscope (Visible, Intertec Medical, Tokyo, Japan). We diagnosed the patient with a tumor thrombus by angioscopic observation of a smooth-surfaced, white, elevated lesion in the IVC that had invaded the vein wall (Figure D, Video ).
Previous reports have demonstrated that FDG-PET and T2-weighted MRI can distinguish benign and tumor thrombi 12. However, clinically, it is not always easy to distinguish between the two. Angioscopy facilitates these distinctions because it visually evaluates. Our report has the potential to serve as a new diagnostic method for tumor thrombus in the future.