Table 1 The International Mesothelioma Interest Group (IMIG) staging system

T1

T1a

Tumor limited to the ipsilateral parietal pleura, including mediastinal and diaphragmatic pleura

No involvement of the visceral pleura

T1b

Tumor involving the ipsilateral parietal pleura, including mediastinal and diaphragmatic pleura

Scattered foci of tumor also involving the visceral pleura

T2

Tumor involving each of the ipsilateral pleura surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following features:

 Involvement of diaphragmatic muscle

 Confluent visceral pleural tumor (including the fissures) or extension of tumor from visceral pleura into the underlying pulmonary parenchyma

T3

Describes locally advanced but potentially resectable tumor

Tumor involving all of the ipsilateral pleural surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following features:

 Involvement of the endotharacic fascia

 Extension into the mediastinal fat

 Solitary, completely resectable focus of tumor extending into the soft tissues of the chest wall

 Nontransmural involvement of the pericardium

T4

Describes locally advanced technically unresectable tumor

Tumor involving all of the ipsilateral pleural surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following features:

 Diffuse extension or multifocal masses of tumor in the chest wall, with or without associated rib destruction

 Direct transdiaphragmatic extension of tumor to the peritoneum

 Direct extension of tumor to the contralateral pleura

 Direct extension of tumor to one or more mediastinal organs

 Direct extension of tumor into the spine

 Tumor extending through to the internal surface of pericardium, with or without a pericardial effusion; or tumor involving the myocardium

N-lymph nodes

 Nx

Regional lymph nodes cannot be assessed

 N0

No regional lymph node metastases

 N1

Metastases in the ipsilateral bronchopulmonary or hilar lymph nodes

 N2

Metastases in the subcarinal or the ipsilateral mediastinal lymph nodes, including the ipsilateral internal mammary nodes

 N3

Metastases in the contralateral mediastinal, contralateral internal mammary, ipsilateral, or contralateral supraclavicular lymph nodes

M-metastases

 Mx

Presence of distant metastasis cannot be assessed

 M0

No distant metastasis

 M1

Distant metastasis present

Ia

T_1aN₀M₀

Ib

T_1bN₀M₀

II

T₂N₀M₀

III

AnyT₃M₀

AnyN₁M₀

AnyN₂M₀

IV

AnyT₄

AnyN₃

AnyM₁