[A case report of a pseudoaneurysm of the thoracic aorta (thrombotic closure type) showing like a mediastinal tumor--value of endoscopic ultrasonography in differential diagnosis].

A 65-year-old male patient was refered to our hospital for abnormal mediastinal shadow. CT and MRI study showed an inhomogeneous mediastinal tumor simulating neoplasm neighboring the aortic arch. Thoracic aortogram did not revealed the existence of thoracic aortic aneurysm. But the endoscopic ultrasonography (EUS) showed a pseudoaneurysm with a 2 cm entry site. The diagnosis of pseudoaneurysm was therefore proved, so the patient underwent the operation safely with preparation for extracorporeal circulation. Some patients with chronic thoracic pseudoaneurysm has no history of chest trauma and other causes. It is valuable to perform EUS for the differential diagnosis of abnormal mediastinal shadow which shows like a mediastinal tumor.