Clinical Staging System for Thymoma of Masaoka et al

Masaoka et al proposed a clinical staging system for thymoma in 1981 which is still widely used.

Extent of Tumor	Stage
macroscopically completely encapsulated and microscopically no capsular invasion	I
(1) macroscopic invasion into surrounding fatty tissue, mediastinal pleura, or both (2) microscopic invasion into capsule	II
macroscopic invasion into a neighboring organ (pericardium, great vessel, lung, etc.)	III
pleural and/or pericardial dissemination	IVA
lymphogenous and/or hematogenous metastasis	IVB

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