Masaoka Koga Staging System of Thymic Epithelial Tumors
- I—Macroscopically, completely encapsulated; microscopically, no capsular invasion
- II—Macroscopic invasion into surrounding fatty tissue or mediastinal pleura; or microscopic invasion into capsule
- III—Macroscopic invasion into neighboring organs (pericardium, lung, or great vessels)
- IVA—Pleural or pericardial dissemination
- IVB—Lymphogenous or hematogenous metastases
What is a thymoma?
A thymoma is an uncommon thymic epithelial tumor that is the most common primary tumor of the thymus and of the anterior mediastinum. It occurs in men and women equally and most often occurs after age 40. It is an epithelial neoplasm composed of a mixture of epithelial cells and mature lymphocytes. About 33% are invasive, and the remainder are encapsulated. Complete surgical resection is the major treatment for a thymoma. Radiation therapy or chemotherapy may be used for an invasive thymoma, an incompletely resected thymoma, or a disseminated thymoma. Most patients with an encapsulated thymoma are cured with surgical resection, and many with microscopically invasive thymoma are cured with surgery and adjunctive radiation therapy. Patients with macroscopic invasion often have a prolonged course with slowly growing metastatic disease. The Masaoka-Koga staging system is used in patients with thymoma