[Aneurysms of the azygos vein]

A case of aneurysm of the arch of the greater azygos vein is reported. This extremely rare congenital anomaly appears as a large rounded opacity in the anterosuperior mediastinum. Though diagnosis may be suspected by the variations in size according to the period of observation and the position of the patient, if can only be confirmed by angiography, to eliminate an aneurysm of the superior vena cava or one of azygos vein from obstruction of the inferior vena cava.