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Table 1 Classification of thymomas according to Masaoka-Koga stage [14]

From: A single-center experience: management of patients with thymic epithelial tumors

Stage Masaoka-Koga staging system
I Grossly and microscopically completely encapsulated tumor
II a Microscopic transcapsular invasion
II b Macroscopic invasion into thymic or surrounding fatty tissue, or grossly adherent to but not breaking through mediastinal pleura or pericardium
III Macroscopic invasion into a neighboring organ (i.e., pericardium, great vessel, or lung)
IV a Pleural or pericardial metastases
IV b Lymphogenous or hematogenous metastasis