術前悪性縦隔胚細胞腫瘍を疑った胸腺原発成熟奇形腫とⅠ期胸腺腫の合併例

Concurrent Thymoma and Mature Teratoma in the Mediastinum

胸腺腫の多発発生例はまれに報告されるが，胸腺腫とそれ以外の胸腺原発腫瘍の同時発症例はきわめてまれであり，画像診断が困難である．われわれは術前に正確な診断が行えなかった，胸腺原発成熟奇形腫とⅠ期胸腺腫の合併例を経験したので報告する．

A 41-year-old asymptomatic male with no significant medical history had a heterogenous cystic tumor with a diameter of 5.1 cm containing fatty density in the anterior mediastinum and a nearby homogeneous enhancing nodule with a diameter of 2.0 cm were observed on chest computed tomography （CT）. A malignant teratoma with mediastinal lymph node metastasis was suspected preoperatively. The tumor was completely removed via median sternotomy, with concomitant resection of the lung, pericardium, and right phrenic nerve. Postoperative pathological examination revealed a large mature cystic teratoma, 6.0 cm in diameter, and a small nodule, 3.7 cm in diameter, diagnosed as stageⅠ, type B2 thymoma. The postoperative course was uneventful, with no recurrence 30 months later. The simultaneous occurrence of mature teratoma and stageⅠthymoma is extremely rare. When suspecting a teratoma with small satellite nodules preoperatively, consideration of concurrent small thymoma is suggested.