Figure 1

History : 23-year-old male with a large mediastinal mass seen on outside chest X-ray (Figure 1) and CT (Figure 2). Biopsy indicated Hodgkins Lymphoma. Patient was referred to Main Street Radiology for whole body PET scan.

Figure 2

Findings : Coronal whole body image (Figure 3) demonstrates multiple hypermetabolic areas (dark) in the mediastimum and neck (small arrows), compatible with lymphadenopathy. Normal physiological activity within the urinary bladder is seen.

Figure 3

On the axial image of the chest (Figure 4), extensive mediastinal lymphadenopathy is seen corresponding to the CT finding. A photopenic (light) area is seen in the mediastinum (arrow on Figure 4) corresponding to necrosis seen on CT (arrow on Figure 2). Abnormal right internal mammary lymph node is also seen on PET (Figure 5), which was not appreciated on CT.

Figure 5
Figure 4

Discussion: Numerous clinical studies have shown that PET is the best imaging modality for lymphoma, superior to CT, MR, and gallium scan. In the management of lymphoma, PET is indicated for initial staging as well as to monitor response to treatment and to exclude recurrence. PET is especially useful in distinguishing tumor from necrosis and fibrosis.