Figure 3. Transaxial (left), coronal (middle), and sagittal (right) 18F-FDG PET scans obtained in a 17-year-old girl who was being treated for lymphoma demonstrate linear uptake in the anterior mediastinum with a maximum SUV of 3.8. Differentiation of lymphoma from thymic hyperplasia is difficult in such cases. A repeat study performed 5 months later showed continued absence of lymphoma with persistent anterior mediastinal uptake in the same triangular configuration. This finding was believed to represent thymic hyperplasia.