[Mediastinal Hemangioma Mimicking a Mature Cystic Teratoma;Report of a Case].

A 16-year old young man was referred to our hospital due to abnormal mass of mediastinum on chest radiography. Chest computed tomography scan revealed 45 mm mass in diameter with low density areas and ring shaped calcification at right upper mediastinum. However, chest magnetic resonance imaging showed no existence of fat nor calcification. Although no typical findings was observed, surgical resection was performed because mature cystic teratoma was undeniable. At complete video-assisted thoracoscopic surgery, tumor was found to be in the upper mediastinum covered with mediastinal pleura and with dense fibrous structures around it, and was resected with surrounding fat tissue. Histological diagnosis was hemangioma associated with lymphangiogenesis and arteriovenous malformation-like region in the surrounding fat tissue.