Mesothelioma Staging: TNM System Guide

Mesothelioma staging describes how far the cancer has spread at the time of diagnosis. Stage plays a critical role in determining treatment options, eligibility for surgery, and expected survival. Understanding your stage helps you make informed decisions about your care.

The TNM Staging System

Pleural mesothelioma is staged using the TNM system developed by the American Joint Committee on Cancer (AJCC). The current 8th edition staging criteria, implemented in 2018, classify tumors based on three factors:

T (Tumor): How far the primary tumor has grown into surrounding tissues.

N (Nodes): Whether cancer has spread to nearby lymph nodes.

M (Metastasis): Whether cancer has spread to distant organs.

Combining these factors determines the overall stage, from Stage 1 (most localized) to Stage 4 (most advanced).

Stage-by-Stage Breakdown

Stage 1: Localized Disease

Stage 1 mesothelioma is confined to one side of the chest. The tumor involves the pleural lining but has not spread to lymph nodes or distant sites.

Stage 1A (T1, N0, M0): The tumor is limited to the parietal pleura (chest wall lining) on one side. It may have minimal involvement of the visceral pleura (lung lining) but has not grown into deeper structures.

Stage 1B (T2-T3, N0, M0): The tumor has grown more extensively into the pleura or has begun to involve nearby structures such as the diaphragm or lung tissue, but lymph nodes remain negative.

Stage 1 statistics:

• Approximately 9% of cases diagnosed at this stage
• Median survival: 21-24 months with standard treatment
• Median survival with multimodal treatment: 32+ months
• 5-year survival rate: 15-20%

Most Stage 1 patients are candidates for surgical resection, which significantly improves outcomes.

Stage 2: Limited Regional Spread

Stage 2 indicates the tumor has grown more extensively on one side of the chest and may involve ipsilateral (same-side) lymph nodes.

Stage 2 (T1-T2, N1, M0): The tumor remains localized to the pleura but has spread to nearby lymph nodes on the same side of the chest.

Stage 2 statistics:

• Approximately 15% of cases diagnosed at this stage
• Median survival: 14-19 months with standard treatment
• Median survival with multimodal treatment: 24+ months
• 5-year survival rate: 10-15%

Many Stage 2 patients remain surgical candidates, particularly those with good overall health.

Stage 3: Advanced Regional Disease

Stage 3 mesothelioma has spread more extensively within the chest but has not reached distant organs.

Stage 3A (T3, N1, M0): The tumor has grown into deeper structures (diaphragm, pericardium, or chest wall muscles) and involves ipsilateral lymph nodes.

Stage 3B (T1-T3, N2, M0): Lymph node involvement has extended to contralateral (opposite side) or more distant chest lymph nodes.

Stage 3 statistics:

• Approximately 35% of cases diagnosed at this stage
• Median survival: 12-16 months with standard treatment
• 5-year survival rate: 5-10%

Surgical options become more limited at Stage 3. Some patients may still be candidates for surgery as part of multimodal treatment, but many receive chemotherapy and immunotherapy as primary treatment.

Stage 4: Metastatic Disease

Stage 4 mesothelioma has either invaded structures that make surgical removal impossible (T4) or has spread to distant organs (M1).

Stage 4 characteristics may include:

• Tumor extending through the diaphragm into the abdomen
• Involvement of the spine, heart, or major blood vessels
• Tumor on both sides of the chest
• Metastasis to distant organs (liver, bone, brain, distant lymph nodes)

Stage 4 statistics:

• Approximately 40% of cases diagnosed at this stage
• Median survival: 8-12 months with standard treatment
• 5-year survival rate: Less than 5%

Treatment focuses on controlling symptoms, maintaining quality of life, and extending survival through systemic therapies.

Survival Rates by Stage

Overall survival statistics vary based on treatment approach:

Stage	Standard Treatment	Multimodal Treatment	5-Year Rate
Stage 1	21-24 months	32+ months	15-20%
Stage 2	14-19 months	24+ months	10-15%
Stage 3	12-16 months	Variable	5-10%
Stage 4	8-12 months	N/A (non-surgical)	Less than 5%

These statistics reflect population averages. Individual outcomes vary based on cell type, overall health, treatment response, and other factors.

How Staging Is Determined

Staging requires comprehensive evaluation using multiple diagnostic methods:

Imaging studies:

• CT scans: Primary tool for evaluating tumor extent and lymph node involvement
• PET scans: Help identify metabolically active tumor and distant metastases
• MRI: Provides detailed evaluation of chest wall and diaphragm involvement

Tissue sampling:

• Biopsy: Confirms diagnosis and determines cell type (epithelioid, sarcomatoid, or biphasic)
• Lymph node sampling: May be performed during biopsy or staging surgery

Surgical staging:

• Video-assisted thoracoscopic surgery (VATS): Allows direct visualization and sampling
• Mediastinoscopy: Evaluates lymph nodes in the center of the chest
• Endobronchial ultrasound (EBUS): Less invasive lymph node evaluation

Accurate staging requires experienced radiologists and surgeons familiar with mesothelioma patterns. Misdiagnosis of stage can lead to inappropriate treatment recommendations.

Why Stage Matters for Treatment

Staging directly influences treatment recommendations:

Stages 1-2 (potentially resectable):

• May be candidates for extrapleural pneumonectomy (EPP) or pleurectomy/decortication (P/D)
• Multimodal treatment combining surgery with chemotherapy and/or immunotherapy offers best outcomes
• Surgery typically preceded or followed by systemic therapy

Stage 3 (borderline resectable):

• Surgical options evaluated case by case based on specific tumor characteristics
• Many patients receive systemic therapy as primary treatment
• Clinical trials may offer access to newer approaches

Stage 4 (unresectable):

• Focus on systemic therapy (chemotherapy, immunotherapy)
• Palliative treatments address symptoms
• Clinical trials may provide access to experimental therapies
• Quality of life optimization becomes primary goal

Peritoneal Mesothelioma Staging

Peritoneal mesothelioma (affecting the abdominal lining) uses a different staging system: the Peritoneal Cancer Index (PCI).

The PCI divides the abdomen into 13 regions and scores tumor involvement in each region from 0 to 3. Total scores range from 0 to 39:

PCI Score	Description	Surgery Consideration
0-10	Limited disease	Good candidate for cytoreduction
11-20	Moderate disease	Case-by-case evaluation
21-39	Extensive disease	Surgery often not beneficial

Patients with limited disease who undergo cytoreductive surgery with heated intraperitoneal chemotherapy (HIPEC) can achieve median survival exceeding 5 years in some studies.

Factors That Affect Prognosis Beyond Stage

While stage is important, other factors significantly influence outcomes:

Cell type:

• Epithelioid: Best prognosis (60-70% of cases)
• Sarcomatoid: Poorest prognosis (10-20% of cases)
• Biphasic: Intermediate (depends on proportion of each type)

Performance status:

• Patients who are more active and functional at diagnosis typically have better outcomes regardless of stage

Age:

• Younger patients generally tolerate aggressive treatment better

Biomarkers:

• BAP1 mutations may indicate better prognosis
• PD-L1 expression may predict response to immunotherapy

Treatment center:

• Patients treated at specialized mesothelioma centers tend to have better outcomes than those treated at general oncology practices

Getting an Accurate Diagnosis

Given the importance of accurate staging, patients should:

• Request comprehensive imaging: Staging requires CT and often PET scans. MRI may be needed for specific questions about local invasion.
• Ensure adequate tissue sampling: Accurate cell typing requires sufficient biopsy material evaluated by an experienced pathologist.
• Ask about staging surgery: If surgery might be an option, staging laparoscopy or thoracoscopy can provide more accurate information than imaging alone.

Related Articles

• Mesothelioma Diagnosis Explained
• Mesothelioma Treatment Options
• Multimodal Treatment
• Mesothelioma Surgery Options
• Mesothelioma Prognosis
• Mesothelioma Clinical Trials