Figure 1. Enhanced CT scan in a 37-year-old woman with lymphoma demonstrating enlarged pre-vascular (arrowheads) and left upper paratracheal (arrow) nodes, encasing the patent left carotid (C) and left subclavian (S) arteries. Lack of vessel invasion or constriction is a feature that may be helpful for distinguishing lymphoma from metastatic carcinoma. (From Glazer HS, Semenkovich JW, Gutierrez FR. Mediastinum. In: Lee JKT, Sagel SS, Stanley RJ, Heiken JP, editors. Computed body tomography with MRI correlation, 3rd edn. Philadelphia, PA: Lippincott-Raven Publishers, 1998:261–349 [13]. Reprinted with permission).