A case of atypical type A thymoma with vascular invasion and lung metastasis.

We present a case of type A thymoma with invasion of the left brachiocephalic vein and lung metastases. An 84-year-old man underwent extended thymectomy combined with left brachiocephalic vein reconstruction and resection of a lung metastasis. Histological examination showed vascular invasion by the tumor. The lung metastasis had high mitotic activity and slight nuclear enlargement, the so-called "atypical" features, but the main part of the primary tumor did not. However, the intravascular portion of the tumor had "atypical" histological features like the lung metastasis. It seems that "atypical" histological features are related to clinically malignant behavior.