Minimally invasive thymoma with extensive intravascular growth.

A 70-year-old male with grossly non-invasive thymic tumor associated with myasthenia gravis was subjected to thymothymectomy. Microscopic examination showed extensive intravascular tumor extensions into veins of thymic tissue and surrounding muscles and a minute direct invasion of the thymic tissue. Histologically, the tumor showed mixed-type thymoma with polygonal epithelial cells. These pathological findings indicated that the tumor cells extended mainly into vessels beyond the tumor capsule via tumor drainage veins rather than invading neighboring structures. After chemotherapy and mediastinal irradiation, the patient is now in complete remission of myasthenia gravis and is recurrence-free 15 months after surgery.