[Lung metastasis of thymic carcinoma twelve years after complete resection of primary disease].

We report a 67-year-old woman who developed lung metastasis 12 years after resection of the mediastinal tumor which was diagnosed as B3-thymoma. Combined resection of bilateral lungs and left innominate vein was performed due to tumorimvasion. 12 years later, she was diagnosed as having primary lung adenocarcinoma with bronchoscopic examination and cytology. Postoperative histological and immunohistochemical examination showed that the lung nodule was a lymphoepithelioma-like carcinoma of the thymus with strong immunoreactivity for CD5 and bcl-2. Reexamination by immunohistochemical staining for CD5 and bcl-2 revealed that the disease diagnosed as thymoma 12 years ago was also thymic carcinoma Accurate differential diagnosis between B3-thymoma and thymic carcinoma is essential for choosing appropriate postoperative treatment.