Although there is no standardised UICC staging system, the system cited by Masaoka, 1981 is commonly employed.
Intact capsule or growth within the capsule
Invasion into surrounding fatty tissue or mediastinal pleura
Stage II A:
microscopic invasion through capsule
Stage II B:
macroscopic and microscopic invasion through capsule
Macroscopic invasion into neighbouring organs (pericardium, great vessels, lung)
Pleural or pericardial dissemination
Lymphogenous or hematogenous metastasis
Masaoka A, Monden Y, Nakahara K, et al: Follow-up study of thymomas with special reference to their clinical stages. Cancer 1981;48:2485-2492.
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