TNM Staging System

TNM stands for tumor, nodes, metastasis. The original TNM system was developed by French physician Pierre Denoix in the 1940s, and since then it has evolved and developed into a standard basis for staging many different types of cancer.

Several TNM systems have been designed specifically for mesothelioma over the years. One of the first mesothelioma-specific TNM staging systems was developed by A. P. Chahinian in the early 1980s.

The first attempt to create an internationally used TNM staging system for mesothelioma took place in 1990 with a system proposed by the International Union Against Cancer (UICC). In 1994, the International Mesothelioma Interest Group (IMIG) came together to develop a newer, more comprehensive TNM staging system for mesothelioma, which was eventually published in October 1995.

Current TNM Stages for Mesothelioma

The TNM system used today was approved by both the UICC and the American Joint Committee on Cancer (AJCC). The most recent version of the TNM staging guidelines were published in the 7th edition of the AJCC Cancer Staging Manual (2009) – a new (8th) edition of the manual is projected for publication in 2016 with an effective year of 2017.

The AJCC-UICC Staging System involves two steps: determining the status of the primary tumor, the lymph nodes, and any metastasis, and then identifying the appropriate stage based on the status of those factors. In any case where an assessment cannot be made, the number is substituted with an X for each factor.

TNM Staging System for Mesothelioma (AJCC-UICC)

Primary tumor

T0 No evidence of primary tumor
T1 Tumor involves ipsilateral parietal pleura
T1a Tumor involves ipsilateral parietal (mediastinal, diaphragmatic) pleura with no involvement of the visceral pleura
T1b Tumor involves ipsilateral parietal (mediastinal, diaphragmatic) pleura with focal involvement of visceral pleura
T2Tumor involves any of the ipsilateral pleural surfaces with at least one of the following:
invasion of diaphragmatic muscle
extension into the lung parenchyma

T3
Describes locally advanced but potentially resectable tumor (i.e., it might be possible to remove it)
Tumor involves any of the ipsilateral pleural surfaces with at least one of the following:
invasion of the endothoracic fascia
invasion into mediastinal fat
solitary, completely resectable focus of tumor invading the soft tissues of the chest wall
non-transmural involvement of the pericardium

T4
Describes locally advanced technically unresectable tumor (i.e., it cannot be removed)
Tumor involves any of the ipsilateral pleural surfaces with at least one of the following:
diffuse or multifocal masses in the chest wall (with or without rib destruction)
invasion through the diaphragm to the peritoneum
direct extension to the contralateral pleura
extension to mediastinal organs
invasion into the spine
extension through the internal surface of the pericardium (with or without a pericardial effusion or involvement of the myocardium)

Regional lymph nodes (N)

N0 No regional lymph node metastasis
N1 Metastasis in the ipsilateral bronchopulmonary and/or hilar lymph nodes
N2 Metastasis in the subcarinal lymph nodes, ipsilateral internal mammary, mediastinal lymph nodes, or the peridiaphragmatic lymph nodes
N3 Metastases in the contralateral mediastinal, contralateral internal mammary, or hilar lymph nodes and/or the ipsilateral supraclavicular or scalene lymph nodes

Distant metastases (M)
M0 No distant metastases
M1 Distant metastases present

Overall Stage
IA T1a, N0
IB T1b, N0
II T2, N0
III T1-2, N1-2, T3, N0-2
IV T4, N3, or M1

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