​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

Reference: 

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 for larger image