Mediastinum
Thymoma and related entities
AJCC / TNM staging

Author: Andrey Bychkov, M.D., Ph.D.
Editor-in-Chief: Debra Zynger, M.D.

Revised: 11 October 2018, last major update September 2018

Copyright: (c) 2002-2018, PathologyOutlines.com, Inc.

PubMed Search: Thymoma staging[TI]

Cite this page: Bychkov, A. AJCC / TNM staging. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mediastinumthymomastaging.html. Accessed October 16th, 2018.

Pathologic TNM staging of thymoma and related entities, AJCC 8th edition
Definition / general
  • 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)
Essential features
  • 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
Primary tumor (T)
  • 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

Notes:
  • 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
Regional lymph node (N)
  • 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

Note:
  • Involvement must be microscopically confirmed in pathological staging, if possible
Distant metastasis (M)
  • 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
AJCC prognostic stage grouping
Stage I: T1a, T1b N0 M0
Stage II: T2 N0 M0
Stage IIIA: T3 N0 M0
Stage IIIB: T4 N0 M0
Stage IVA: any T N1 M0
any T N0, N1 M1a
Stage IVB: any T N2 M0, M1a
any T any N M1b
Board review question #1
A 62 year old man presented with a large thymic carcinoma directly invading pericardium and no metastatic spread. What is the pT category per the AJCC/TNM 8th edition?

  1. pT1a
  2. pT1b
  3. pT2
  4. pT3
  5. pT4
Board review answer #1
C. pT2
Board review question #2
What is the major predictor of thymic carcinoma recurrence?

  1. Distant metastasis
  2. Extent of local invasion
  3. Histological type
  4. Nodal metastasis
  5. Size of tumor
Board review answer #2
B. Extent of local invasion. T category (local invasion) is a major predictor of recurrence while N and M categories significantly influence survival.

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