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​5.1 Classific​ation Criteria

Although there is no standardised UICC staging system, the system cited by Masaoka, 1981 is commonly employed.

Stage I
Intact capsule or growth within the capsule

Stage II​
Invasion into surrounding fatty tissue or mediastinal pleura

Stage II A:
microscopic invasion through capsule

Stage II B:
macroscopic and microscopic invasion through capsule

Stage III
Macroscopic invasion into neighbouring organs (pericardium, great vessels, lung)

Stage IVA
Pleural or pericardial dissemination

Stage IVB
Lymphogenous or hematogenous metastasis


  1. 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.

5.2 Staging ​Diagram

Click to enlarge - Thymoma Staging Diagram 

Click for larger image

SOURCE: Staging ( )
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