[Cystic tumors of mediastinum].

Nine of twenty-four mediastinal tumors showed cystic lesions were operated at Kinki University Hospital. These nine mediastinal cysts included 5 of thymic cysts, 3 teratomas and one pericardial cyst. By the preoperative imagings, thymic cysts showed a smooth wall and homogenous content with water density. Teratoma consisted of cystic and solid parts, and the irregular thickness of the wall was found. One of these teratomas was ruptured into the pleural cavity, it has been proposed that digestive enzyme derived from pancreatic tissue with Langerhans island caused autolysis and necrosis with result in rupture. Pericardial cyst located at cardiophrenic angle mostly and which is useful on diagnosis.