The following is a technical discussion of staging for malignant mesothelioma written for health professionals.
The American Joint Committee on Cancer (AJCC) staging system for mesothelioma was adopted from that proposed by the IMIG in 1995 and has been validated in a number of surgically based trials. The system evolved from a greater understanding of the relationships between the tumor (T) status and nodal (N) status and overall survival. There was a redefinition of the T categories, and the T1 lesions were divided into T1a (involvement of the parietal pleura only) and T1b (involvement of the visceral pleura), which led to a split of stage I into state IA and IB. T3 is defined as a locally advanced but potentially resectable tumor, and T4 is defined as a locally advanced, technically unresectable tumor. The Brigham and Woman’s Staging System has also been proposed for pleural mesothelioma and differs from the AJCC by defining intrapleural adenopathy (lymph node involvement near the pleura) as stage II disease and extrapleural adenopathy as stage III disease. The AJCC system classifies any nodal involvement, either intrapleural or extrapleural as stage III disease.
International Staging System for Diffuse Malignant Pleural Mesothelioma
T-TUMOR STATUS
T1
T1a
Tumor limited to the ipsilateral parietal ± mediastinal ± diaphragmatic pleura
No involvement of the visceral pleura
T1b
Tumor involving the ipsilateral parietal ± mediastinal ± diaphragmatic pleura
Tumor also involving the visceral pleura
T2
Tumor 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
Extension of tumor from visceral pleura into the underlying pulmonary parenchyma
T3
Describes locally advanced but potentially respectable 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 endothoracic 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 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 mediastinal organs
Direct extension of tumor into the spine
Tumor extending through to the internal surface of the 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 noes, 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 metastases cannot be assessed
M0: No distant metastasis
M1: Distant metastasis present
STAGE
STAGE I
Ia: T1aN0 M0
Ib: T1bN0 M0
STAGE II
T2 N0 M0
STAGE III
Any T3 M0
Any N1 M0
Any N2 M0
STAGE IV
Any T4
Any N3
Any M1