Example of downstaging by PET-CT. (Left) CT and (right) PET axial images show a case downstaged by PET-CT. (A) There was nodal disease in the mediastinum and a 22-mm lung nodule in the left lung (arrow), reported on CT as stage 4. The PET scan showed high uptake in lymph nodes but no FDG uptake in the lung nodule, suggesting the nodule was unlikely to be due to lymphoma interpreted as stage 2. (B) After treatment, there was resolution of uptake in lymph nodes but the lung nodule (arrow) was unchanged.