The incidence of thrombus is high in patients with underlying malignancy. This thrombus is mostly venous thromboembolism (VTE), but it may rarely be a tumor thrombus (TT). VTE is common in oncologic patients and is treated with anticoagulant treatment agents whereas aggressive treatment approaches are needed in TT. TT may occur in any cancer and has been reported in many different malignancies (ie, solid carcinomas, sarcomas, and hematologic malignancies) with RCC and HCC being considered the most common underlying malignancies1. In literature, there is only retrospective few articles and some case reports on the role of FDG PET-CT imaging 23456. The FDG uptake pattern in TT is not yet as conclusively established, but generally, a linear FDG uptake pattern or more focal FDG accumulation has been reported in literature 23456. In a recent interesting image report from Sonavane SN et al, the authors reported the imaging findings of a patient with RCC where PET/CT not only ruled out locoregional adenopathy and distant metastases, but also distinguished tumor thrombi from benign thrombi in the same patient 7. Incidental detection of secondary malignancies or occult metastases from primary malignant disease on 18F-FDG PET/CT has been reported previously 8910. In this case report, FDG PET-CT imaging was very useful for diagnosis of tumor thrombus in a patient that diagnostic CT scan could not distinguish tumor thrombus & venous thrombus (Figure 1 A-F).