The superior vena cava (SVC) syndrome is a unique clinical entity first described by William Hunter in 1757. The syndrome develops as a consequence of a pathologic process within the mediastinum and is considered an oncologic emergency because of the acute cerebral syndrome that results from venous obstruction and increased intracerebral pressure. If left untreated, venous obstruction in the upper thoracic cavity can progress to stasis of blood flow and eventually to intravascular clotting with major secondary sequelae.