[A case report of invasive thymoma presenting as a solitary metastatic lesion of the lung].

A 66-year-old woman visited our hospital for further investigation of a coin-shaped lesion in the right lower lung field. After admission, CT-scan revealed an anterior mediastinal tumor. Thymoma and lung metastasis from thymoma were suspected. At thoracotomy, an invasive thymoma involving the left phrenic nerve, the left upper lobe, and the pericardium was found, and the diagnosis of lung metastasis was made. Postoperative pathological findings showed a predominantly lymphocytic thymoma with round and oval-shaped epithelial cells, and the metastatic lung lesion revealed the same findings. Postoperative radiotherapy (4000 rads) and chemotherapy with a combination of CDDP, VDS, and CPA were administered. The metastasis of thymoma is not rare, but most often it is found after operation. In this case the diagnosis of metastatic thymoma was made pre-operatively from a solitary lung lesion.