A case of mediastinal mature teratoma complicated by empyema due to rupture into the pleural cavity

A 16-year-old female visited our hospital, complaining of cough, fever, and left precordial pain. Chest computed tomography showed a heterogeneous anterior mediastinal tumor measuring 7 cm in diameter and complete atelectasis in the lingula and lower lobe of the left lung. Magnetic resonance imaging also showed an area of intensity identical to that of adipose tissue in the anterior mediastinal tumor. Thus, empyema due to rupture of a mature teratoma was diagnosed. The empyema was treated with intra-pleural fibrinolytic therapy, drainage, and antibiotics. After confirming resolution of the empyema, we resected the anterior mediastinal tumor and pathologically diagnosed it as cystic mature teratoma. Histopathological examination showed glandular tissue resembling the pancreas, suggesting that the rupture had been caused by pancreatic enzymes in the tumor. Mediastinal mature teratoma carries a risk of serious complications developing due to rupture and the possibility of malignant transformation during the disease course. Thus, early surgical treatment is important.