Well-differentiated adenocarcinoma arising from mature cystic teratoma of the mediastinum (teratoma with malignant transformation). Report of a surgical case.

A surgical case of teratoma with malignant transformation (TMT) of the mediastinum in a 66-year-old man is reported. The unilocular, cystic, mediastinal mass, which had been seen in a chest radiograph 7 years earlier, was extirpated. The mass was histologically revealed to be a mature cystic teratoma containing skin and respiratory epithelial tissues, with some areas of well-differentiated adenocarcinoma. Surgical cases of TMT in the mediastinum, which have not received any preoperative chemotherapy or radiation therapy, are rare. By reviewing the previous literature on TMT in various organs, the authors distinguished two types of TMT, chemotherapy- or radiotherapy-induced TMT and naturally occurring TMT. The pathogenesis of these two types are discussed.