Unusual pattern: Diffuse pulmonary FDG uptake on PET/CT

A 75-year-old nonsmoker and nonalcoholic female, known to have squamous cell carcinoma of the head and neck metastasized to the lungs, was found to have a mass at the right hilar/infra-hilar region and an unusual pattern of increased mild diffuse 18-fluorodeoxyglucose (18-FDG) uptake at the right mid-lower lobe location without any lung parenchymal abnormalities (confirmed by low dose CT scan of PET-CT). It was suspected to be the lymphangitic spread of the neoplasm; however, spectral detector CT (SDCT) imaging performed later not only confirmed the presence of a mass invading the right inferior pulmonary vein but showed a large area of significantly decreased perfusion in the right middle and lower lung lobes, leading to a change in the diagnosis to right pulmonary venous occlusion.