Abstract
A 70-year-old woman was admitted to a local hospital with a five-day history of back pain. She had been referred to our hospital after an abnormal chest shadow was identified on chest X-ray. Chest computed tomography (CT) revealed an anterior mediastinal mass in the upper lobe of the left lung. Her general condition was good. She was diagnosed with lung cancer, and examination was planned. However, respiratory failure rapidly worsened on hospital day 2, and a ruptured pseudoaneurysm of the thoracic aorta (PTA) was diagnosed from contrast-enhanced CT. Emergency thoracic endovascular aortic repair was successfully performed, and her postoperative course was uneventful. The hemodynamics of the PTA were stable in the case of this patient, but the risk of rupture is extremely high and frequently fatal. PTA should therefore be included among the differential diagnoses of mediastinal tumor. KEY POINTS: SIGNIFICANT FINDINGS OF THE STUDY: Pseudoaneurysm of the thoracic aorta (PTA) may present on imaging findings that resemble lung cancer. WHAT THIS STUDY ADDS: PTA should be included among the differential diagnoses of mediastinal tumor. Clinicians therefore need to be familiar with the imaging findings of PTA.