Table 3.

Different staging systems for thymoma.

TNM	Definition	Mazaoka/Koga	Moran
TX	Primary tumor cannot be assessed	NA	NA
T0	No evidence of primary tumor Encapsulated tumor	NA	Encapsulated thymoma
T1	Encapsulated tumor T1a- No mediastinal pleural involvement T1b- Direct invasion of mediastinal pleura	Stage I NA Stag II	Minimally invasive thymoma without involvement of any adjacent structure
T2	Direct invasion of pericardium	Stage III	Stage IIA (innominate vein, mediastinal pleura, lung) Stage IIB (pericardium)
T3	Invasion into lungs, brachiocephalic vein, superior vena cava, phrenic nerve, chest wall, extrapericardial pulmonary artery or veins	Stage III
T4	Invasion into aorta, arch vessels, pulmonary artery, myocardium, trachea, esophagus	Stage III	Stage IIC (great vessels and heart)
M1a, b	M1a: The tumor has spread to the lining of the lung, called the pleura, or the lining of the heart, called the pericardium M1b: The tumor may have spread to the lining of the lung or the heart	Stage IVa: pleural, pericardial dissemination Stage IVb: lymphogenous Hematogenous	Stage III—metastatic disease IIIA—intrathoracic structure Diaphragm (drop metastasis) Lymph nodes IIIB—extrathoracic

NA: not applicable.