• Applicable to thymoma, thymic carcinoma, thymic neuroendocrine tumors, combined thymic carcinoma
• First introduced in AJCC 8th edition (Amin: AJCC Cancer Staging Manual, 8th Edition, 2017)
• AJCC/TNM staging is used for predicting outcomes of thymic tumors, such as recurrence (in the lower stages) and disease specific survival (in the higher stages); reference numbers are available (J Thorac Oncol 2014;9:S65)
• Pre operative clinical staging is based on physical examination and imaging; post operative clinical staging may be supplemented by pathological findings
• Stage is determined primarily by levels of local invasion of a thymic malignancy into surrounding mediastinal structures (T classification) while nodal involvement and metastatic spread are much rarer events
• There is no recommended histologic grading system for thymic tumors
• Other staging systems also exist (Lung Cancer 2014;83:126)

• T, N and M categories are the mainstay for predicting recurrence and survival in patients with thymic tumors
• Local invasion (T category) is the primary determinant of staging

• TX: primary tumor cannot be assessed

• T0: no evidence of primary tumor

• T1: tumor encapsulated or extending into the mediastinal fat, may involve the mediastinal pleura

• T1a: tumor with no mediastinal pleura involvement

• T1b: tumor with direct invasion of mediastinal pleura

• T2: tumor with direct invasion of the pericardium (either partial or full thickness)

• T3: tumor with direct invasion into any of the following: lung, brachiocephalic vein, superior vena cava, phrenic nerve, chest wall or extrapericardial pulmonary artery or veins

• T4: tumor with invasion into any of the following: aorta (ascending, arch or descending), arch vessels, intrapericardial pulmonary artery, myocardium, trachea, esophagus

• Involvement must be microscopically confirmed in pathological staging, if possible
• T categories are defined by levels of invasion; they reflect the highest degree of invasion regardless of how many other (lower level) structures are invaded

• T1, level 1 structures: thymus, anterior mediastinal fat, mediastinal pleura

• T2, level 2 structures: pericardium

• T3, level 3 structures: lung, brachiocephalic vein, superior vena cava, phrenic nerve, chest wall, hilar pulmonary vessels

• T4, level 4 structures: aorta (ascending, arch or descending), arch vessels, intrapericardial pulmonary artery, myocardium, trachea, esophagus

• NX: regional lymph nodes cannot be assessed

• N0: no regional lymph nodes metastasis

• N1: metastasis in anterior (perithymic) lymph nodes

• N2: metastasis in deep intrathoracic or cervical lymph nodes

• Involvement must be microscopically confirmed in pathological staging, if possible

• M0: no pleural, pericardial or distant metastasis

• M1: pleural, pericardial or distant metastasis

• M1a: separate pleural or pericardial nodule(s)

• M1b: pulmonary intraparenchymal nodule or distant organ metastasis

1. pT1a
2. pT1b
3. pT2
4. pT3
5. pT4

1. Distant metastasis
2. Extent of local invasion
3. Histological type
4. Nodal metastasis
5. Size of tumor