A superior vena cava aneurysm discovered by chance at regular physical examination.

A superior vena cava (SVC) aneurysm is a rare disease that can be confused with upper mediastinal tumor. A 57-year-old female visited our hospital regarding an abnormal shadow in her mediastinum on a chest X-ray. Upon closer examinations, which included three-dimensional computed tomography, we diagnosed it as a SVC aneurysm. Since her SVC aneurysm was regarded as fusiform type at low risk of rupture and thrombosis, she has been managed conservatively and is free from any complications to date. Thus, it is important to keep SVC aneurysms in mind during routine examinations.