Thoracic duct cyst of the mediastinum.

Thoracic duct cysts of the mediastinum are extremely rare. The etiology may be related to a congenital or degenerative weakness in the wall of the thoracic duct. They are generally asymptomatic but may sometimes cause pressure effects on adjacent structures. Imaging studies are supportive but not diagnostic. Excision of these cysts is required for diagnosis and to prevent complications. We describe a 49-year old man who presented to us with hoarseness and a fixed right vocal cord. Computed tomography (CT) showed a cystic posterior mediastinal mass in the right paratracheal region. We performed a posterolateral thoracotomy and found the cyst arising from the thoracic duct and contained chylous fluid with a high lipid concentration. We dissected the cyst from the surrounding structures and excised it. Histopathology revealed a cyst lined by a single layer of endothelial cells. He is asymptomatic now one year after surgery.