Pulmonary Arterial Tumor Embolism From Recurrent Metastatic Renal Cell Carcinoma on FDG PET/CT

A 55-year-old man with renal cell carcinoma extending into the renal vein/inferior vena cava (status post nephrectomy and inferior vena cava thrombectomy, pT3bN0M0), and perioperative pulmonary bland thromboembolism (resolved with 3-month of anticoagulation), followed by 3.5 years of complete remission, developed new incidental pulmonary arterial filling defects on a surveillance CT examination (asymptomatic, normal d-dimer, no deep vein thrombosis). Despite anticoagulation, the filling defects not only persisted but also demonstrated intense FDG activity on a restaging PET/CT performed 4 months later for new pulmonary oligometastasis. The FDG activity resolved after systemic immunotherapy, which suggested the retrospective diagnosis of pulmonary arterial tumor emboli, a rare finding.