A 19-year-old, white, male patient presented with acute chest pain in the right hemithorax and moderate dyspnea. A chest X-ray showed that he was suffering from spontaneous pneumothorax. A tomography of the chest was conducted, which showed a large mass in the upper mediastinum. After angiotomography had been performed, this was identified as a large, saccular aneurysm of the brachiocephalic trunk with a maximum diameter of 7.2 cm (Figure 1).