Figure 12c. Lymphoma in a 36-year-old man with a history of Hodgkin disease who was referred for posttherapy evaluation for possible residual disease. Axial CT (a), PET (b), and PET-CT fusion (c) images demonstrate a convex right mediastinal hypermetabolic focus (arrow) that is suspicious for residual disease. Although the unilateral manifestation and midmediastinal location of this focus and the presence of associated other abnormal foci of mediastinal uptake do not support thymic rebound, the pattern of uptake resembles thymic uptake. This pattern may be confusing in certain clinical settings, particularly when the pathologic uptake is located more anteriorly in the mediastinum.