International Mesothelioma Interest Group (IMIG) Staging System for Diffuse Malignant Pleural Mesothelioma

T = tumour

T1a Tumour limited to the ipsilateral pleura including mediastinal and diaphragmatic pleura. No involvement of the visceral pleura.     

T1b Tumour involving the ipsilateral parietal pleura, including mediastinal  and diaphragmatic pleura. Scattered foci of tumour also involving the visceral pleura.

T2 Tumour involving each of the ipsilateral pleural surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following features:

·         involvement of diaphragmatic muscle

·         confluent visceral pleural tumour (including the fissures) or

·         extension of tumour from visceral pleura into underlying pulmonary parenchyma

T3 Describes locally advanced but potentially resectable tumour. Tumour involving all of the ipsilateral pleural surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following features:

·         involvement of the endothoracic fascia

·         extension into the mediastinal fat

·         soltary, completely resectable focus of tumour extending into the soft tissues of the chest wall

·         non-transmural involvement of the pericardium

 T4 Describes locally advanced technically unresectable tumour. Tumour involving all of the ipsilateral pleural surfaces surfaces (parietal, mediastinal, diaphragmatic, and visceral pleura) with at least one of the following features:

·         diffuse extension or multifocal masses of tumour in the chest wall, with or without associated rib destruction

·         direct transdiaphragmatic extension of tumour to the peritoneum

·         direct extension of tumour to the contralateral pleura

·         direct extension of tumour to one of more mediastinal organs

·         direct extension of tumour into the spine

·         tumour extending through to the internal surface of the pericardium with or without a pericardial effusion, or tumour involving the myocardium

N = Lymph nodes

Nx Regional lymph nodes cannot be assessed

N0 No regional node metastases

N1 Metastases in the ipsilateral bronchopulmonary or hilar lymph nodes

N2 Metastases in the subcarinal or ipsilateral mediastinal lymph nodes, including the ipsilateral mammary nodes

N3 Metastases in the contralateral mediastinal, contralateral internal mammary, ipsilateral or contralateral supraclavicular lymph nodes

M = Metastases

MX Presence of distant metastases cannot be assessed

M0 No distant metastasis

M1 Distant metastasis present 

Stage summary

Stage                                 Description

Stage Ia                             T1a N0 M0

Stage Ib                             T1b N0 M0

Stage II                              T2 N0 M0

Stage III                             Any T3 M0

                                          Any N1 M0

                                          Any N2 M0

Stage IV                             AnyT4

                                          Any N3

                                          Any M1

 From Rusch VW. A proposed new international TNM staging system for malignant pleural mesothelioma. Chest 108(4): 1122-1128, 1995

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