Lung Cancer Stages: TNM, Stage 0 to Stage 4

Lung cancer staging describes the size and location of a tumour, whether cancer has spread to nearby lymph nodes and whether it has spread to other parts of the body. The stage helps the healthcare team understand the extent of the cancer, discuss prognosis and plan appropriate care.

Non-small cell lung cancer (NSCLC) has five main stage groups: Stage 0, Stage I, Stage II, Stage III and Stage IV. Higher numbers generally indicate a more advanced stage of disease. Small cell lung cancer (SCLC) is commonly grouped as limited-stage or extensive-stage, although the TNM system may also be used.

The stage is different from the type of lung cancer. Type describes the cancer cells seen under a microscope. Stage describes where the cancer is in the body. Both are important when deciding on treatment. Understanding lung cancer stages can help people discuss their diagnosis and care.

What Does a Lung Cancer Stage Mean?

Lung cancer stages provide a shared way for respiratory physicians, thoracic surgeons, medical oncologists, radiation oncologists, radiologists and pathologists to describe the cancer.

The National Cancer Institute describes the staging process as determining how much cancer is present and whether the cancer has spread. Across lung cancer stages, the same terms help the team communicate clearly.

Staging helps the healthcare team:

• Identify whether the cancer is localised, regionally advanced or metastatic
• Assess whether the cancer can potentially be removed with surgery
• Select appropriate imaging and tissue tests
• Plan surgery, radiotherapy, systemic cancer treatment or a combination
• Discuss lung cancer prognosis and follow-up
• Compare findings before and after treatment

Earlier lung cancer stages often allow cancer treatment with curative intent. This means the treatment aims to remove or destroy all detectable cancer. Surgery commonly forms part of treatment for early-stage non-small cell lung cancer when the person is medically fit, and the tumour can be removed completely.

As the stage increases, treatment is more likely to involve a combination of therapies. However, the stage does not describe every feature of the disease. The cancer type, molecular biomarkers, lung function, overall health and response to treatment also influence the treatment plan and lung cancer prognosis.

The TNM Staging System for Lung Cancer

The TNM staging system distinguishes lung cancer stages by the anatomical extent of disease. It is used for NSCLC and can also provide detailed staging information for SCLC.

The ninth edition of the international TNM classification took effect in 2025. It provides additional detail about the pattern of lymph node involvement and distant spread.

The T, N and M findings are combined to give an overall stage number. For example, a small primary tumour with no nodal or distant spread may be Stage I. A similarly sized tumour involving particular nodes may have a higher stage.

Cancer in a lymph node does not automatically mean metastatic disease. Nodes within the regional drainage area are classified from N1 to N3. Metastatic disease generally requires distant spread or specific findings involving the other lung, pleura or pericardium.

Tumour Categories

The T category considers more than the primary tumour’s diameter. It also considers its location and whether it has reached nearby tissues.

In general:

• T1 tumours measure 3 centimetres or less.
• T2 tumours measure more than 3 centimetres but no more than 5 centimetres, or have particular features involving the main bronchus, visceral pleura or part of the lung.
• T3 tumours measure more than 5 centimetres but no more than 7 centimetres, or involve certain nearby structures such as the chest wall. A separate tumour nodule in the same lobe of the same lung is also classified as T3.
• T4 tumours measure more than 7 centimetres or involve particular central structures. These include the diaphragm, mediastinum, heart, great vessels, recurrent laryngeal nerve, carina, trachea, oesophagus or vertebra. The great vessels are the large blood vessels connected to the heart. A separate tumour nodule in another lobe of the same lung is classified as T4.

For a partly solid lung nodule, clinical staging measurements may focus on the solid component seen on CT. Pathological staging may use the size of the invasive component found when the tissue is examined.

Lymph Node Categories

Lymph nodes filter lymphatic fluid and help the immune system respond to infection and disease. Lung cancer can enter the lymphatic system and spread to lymph nodes within the lung or chest.

The nodal categories generally mean:

• N0: No cancer found in the nodes assessed.
• N1: The cancer has spread to nearby lymph nodes within the affected lung, or to hilar nodes near the same-side bronchus or lung hilum.
• N2: The cancer has spread to nearby lymph nodes in the same-side mediastinal or subcarinal area in the centre of the chest.
• N3: The cancer has spread to lymph nodes in the opposite-side mediastinal or hilar area, or to certain nodes above the collarbone.

The current TNM system divides N2 disease into N2a for a single involved mediastinal lymph node station and N2b for multiple involved mediastinal stations. This distinction can affect the overall stage and treatment planning.

Metastasis Categories

Metastasis means that lung cancer has spread beyond its original regional area or primary site.

• M0 means no distant spread has been identified.
• M1a means cancer has spread within the chest, such as to the other lung, pleural or pericardial tumour deposits, or a malignant pleural or pericardial effusion.
• M1b means cancer has spread to a single site outside the chest. This may be a distant lymph node or a site in one of the distant organs, such as an adrenal gland.
• M1c means cancer has spread to multiple sites outside the chest, including distant lymph nodes, distant organs or other tissues.

The current classification further divides M1c into multiple metastases within one organ system and distant metastasis involving multiple organs.

Non-Small Cell Lung Cancer Stages

The stages of lung cancer for NSCLC range from Stage 0 to Stage IV.

These descriptions provide a general overview. The exact stage depends on the individual combination of T, N and M categories. These lung cancer stages describe anatomical spread, not the cancer’s microscopic subtype.

Stage 0 Lung Cancer

Stage 0 is also called carcinoma in situ. Abnormal cells and cancer cells are present in the lining of an airway or lung structure but have not invaded deeper tissue.

Stage 0 may include adenocarcinoma in situ or squamous cell carcinoma in situ. Because the cells have not become invasive, local treatment with curative intent may be considered. The appropriate approach depends on the location, pathological diagnosis and the person’s ability to undergo a procedure.

Stage I Lung Cancer

Stage I lung cancer remains confined to one lung and has not spread to nearby lymph nodes or distant parts of the body. It is divided into Stage IA and Stage IB.

Stage IA includes smaller tumours and is further divided into Stage IA1, IA2 and IA3 according to tumour size and pathological features. Stage IB generally involves a somewhat larger single tumour or one with particular local features, but there is still no lymph node spread.

Early-stage lung cancer is often treated surgically when the tumour can be removed, and the person is medically fit. Depending on the tumour’s size and location, surgery may involve removing a small section of lung, an anatomical segment or a lobe. Focused radiotherapy may be considered when surgery is unsuitable.

Additional systemic treatment may be recommended for selected cancers based on tumour features, biomarker results and the risk of recurrence.

Stage II Lung Cancer

Stage II lung cancer has not spread to distant parts of the body. It is divided into Stage IIA and Stage IIB.

This stage may involve a larger tumour, growth into certain nearby structures such as the chest wall, or cancer that has spread to nearby lymph nodes. Under the current TNM classification, some small tumours involving a single same-side mediastinal lymph node station may also fall within Stage IIB.

Surgery may form part of cancer treatment for resectable disease. Chemotherapy and selected immunotherapy may be given before or after surgery, depending on the tumour, lymph node findings, molecular biomarkers and overall health. Selected targeted therapy may be used after surgery when molecular testing identifies an eligible alteration. Radiotherapy may also be used in selected circumstances.

Stage III Lung Cancer

Stage III lung cancer is usually described as locally advanced lung cancer. It has spread further within the chest but has not produced distant metastasis. This stage is divided into Stage IIIA, IIIB and IIIC. The group ranges from Stage IIIA to Stage IIIC. Stage IIIC generally reflects more extensive disease within the chest.

The cancer may involve mediastinal nodes, several nodal stations, nodes on the opposite side of the chest or nodes above the collarbone. The primary tumour also may have reached the chest wall, large blood vessels or other structures near the lung.

Locally advanced disease includes a wide range of patterns. Some Stage IIIA cancers may be treated with surgery as part of a combined plan involving chemotherapy, immunotherapy or radiotherapy. Other cancers in this group are generally managed without surgery, often using chemotherapy and radiotherapy followed by additional systemic treatment where appropriate.

Multidisciplinary review is important because the location and number of involved nodes can change the treatment plan.

Stage IV Lung Cancer

Stage IV lung cancer is also called metastatic lung cancer. It is divided into Stage IVA and Stage IVB.

Stage IVA may mean that cancer has:

• Formed a separate tumour in the opposite lung
• Reached the pleura or pericardium
• Caused a malignant pleural or pericardial effusion
• Spread to one site outside the chest

Stage IVB means the cancer has spread to multiple sites outside the chest, including distant lymph nodes. These distant metastases may occur within one organ system or across multiple organs.

Systemic treatment commonly forms the basis of care when cancer is at an advanced stage. Treatment options may include chemotherapy, immunotherapy, targeted therapy or combinations of these treatments. Targeted therapy is used when molecular testing identifies a gene alteration for which an appropriate medicine is available.

The choice also depends on the lung cancer type, PD-L1 results, previous treatment, symptoms and overall health. Surgery, radiotherapy or another local procedure may be used in selected situations to manage a specific site, relieve symptoms or treat a limited metastatic pattern.

More detailed information is available in the guide to metastatic lung cancer treatment.

Small Cell Lung Cancer Stages

Small cell lung cancer can be described using TNM staging, but doctors commonly use two broader groups because this cancer often grows and spreads early.

Limited-stage SCLC is commonly managed with chemotherapy and chest radiotherapy. Extensive-stage SCLC is generally treated with systemic therapy, which may include chemotherapy and immunotherapy.

Surgery has a limited role in SCLC. It may be considered only for uncommon, very early cases after imaging tests and invasive nodal staging confirm that the disease remains localised.

How Is the Lung Cancer Stage Determined?

To determine lung cancer stages, some imaging tests used to make a lung cancer diagnosis also provide staging information. Other tests are performed specifically to look for lymph node involvement or distant spread. Not every person needs every staging test.

Lung cancer is a common cancer worldwide, but risk factors for developing lung cancer and common symptoms such as a persistent cough or chest pain do not show how far the cancer has spread. Diagnosis and staging require appropriate tests.

CT Scan

A contrast-enhanced CT scan shows the primary tumour’s size and location. It also looks for enlarged nodes, additional lung nodules or masses and abnormalities in the chest wall, liver or adrenal gland.

A CT scan can suggest that cancer has spread, but imaging alone may not confirm whether an abnormal area contains cancer.

PET-CT Scan

A PET-CT scan shows areas with increased metabolic activity. It can help assess nodes and look for spread elsewhere in the body.

Infection and inflammation may also appear active on PET-CT. A suspicious PET-CT finding may therefore require tissue sampling or, when an abnormal fluid collection is present, fluid sampling before it changes the treatment plan.

Brain MRI

A brain MRI looks for cancer that has spread to the brain. It may be recommended for SCLC, suspected higher-stage NSCLC or when neurological symptoms are present.

EBUS and Lymph Node Sampling

Endobronchial ultrasound, also called EBUS, combines bronchoscopy with ultrasound. It allows a doctor to examine and take samples from lymph nodes in the centre of the chest.

Sampling can confirm whether an enlarged or PET-active node contains cancer. This distinction may change the N category, overall stage and suitability for surgery.

Mediastinoscopy

Mediastinoscopy is a surgical procedure used to sample mediastinal lymph nodes. It may be considered when less invasive tests have not provided enough information or when additional confirmation is needed before major lung surgery.

Biopsy of a Suspected Metastasis

When imaging shows a possible distant metastasis, the healthcare team may recommend taking a tissue sample from that site or, if the suspected site is an abnormal fluid collection, a fluid sample. Confirming distant spread can prevent treatment decisions based on an uncertain scan finding.

Lung function tests, cardiac assessment, and blood tests may also be performed. These tests help assess fitness for treatment but do not determine the cancer stage.

Clinical and Pathological Staging

A lung cancer diagnosis may have more than one staging description.

Clinical Stage

The clinical stage, written with a “c” before TNM, is based on information available before treatment. This may include CT, PET-CT, MRI, bronchoscopy, EBUS and biopsy results.

This stage guides initial treatment planning.

Pathological Stage

The pathological stage, also called the pathologic stage in some sources and written with a “p” before TNM, uses the tissue removed during surgery. Examination of the tumour and nodes may reveal findings that were not visible on scans.

The pathological stage may therefore differ from the pre-treatment stage. It helps determine whether further treatment should be considered after surgery.

Stage After Initial Treatment

When chemotherapy, immunotherapy or radiotherapy is given before surgery, the prefix “y” may be added to the staging description. This records the extent of the cancer after initial treatment.

If lung cancer returns, doctors describe it as recurrent cancer and record its current location and extent. The stage at the original diagnosis remains part of the medical record.

Why Can the Stage Change During Assessment?

An initial stage may be provisional. A scan might show a suspicious node, but a biopsy may find inflammation rather than cancer. Alternatively, nodal sampling or surgery may identify cancer that was not visible on imaging.

More than one lung nodule can also make staging complex. Multiple tumours in the same lobe, another lobe of the same lung or the other lung may affect the T or M category. However, some nodules are separate primary lung cancers rather than spread from one tumour.

The healthcare team may review imaging, pathology and, when needed, molecular findings together before confirming the stage.

How Lung Cancer Staging Guides Treatment

Lung cancer stages provide an anatomical framework, but they do not determine cancer treatment on their own.

In broad terms:

• Stage 0 and Stage I non-small cell lung cancers often receive local treatment with curative intent. Surgery is commonly considered, while focused radiotherapy may be used when surgery is unsuitable.
• Stage II and selected Stage IIIA cancers may be treated with surgery and systemic therapy. Radiotherapy may be added in selected circumstances.
• Unresectable locally advanced cancer is often managed with combined systemic treatment and radiotherapy.
• Metastatic cancer is usually treated primarily with systemic therapy. Treatment options may include chemotherapy, immunotherapy and targeted therapy when an actionable molecular alteration is present.
• Surgery or radiotherapy may still have a role in selected advanced cases or to relieve symptoms.

The healthcare team also considers:

• The lung cancer type and subtype
• Molecular biomarkers and PD-L1 expression
• Whether the tumour can be removed completely
• The number and location of involved lymph nodes
• Lung and heart function
• Other health conditions
• Previous treatment
• The person’s preferences and treatment goals

Resectability and operability are different. Resectability describes whether the cancer can be removed completely from a technical and cancer-control perspective. Operability describes whether the person is medically fit enough to undergo the proposed operation.

Detailed information about imaging, biopsy and systemic therapies belongs in the guide to lung cancer diagnosis and treatment. Information about surgical eligibility, pulmonary resections, risks and recovery is covered in the guide to lung cancer surgery.

Does the Lung Cancer Stage Predict Prognosis?

The stages of lung cancer are important factors in lung cancer prognosis. In general, prognosis decreases as the stage increases because advanced cancer has spread further and is less likely to be removed or treated with local therapy alone.

Population data from sources such as the National Cancer Institute and American Cancer Society show that five-year survival falls markedly between early-stage, localised lung cancer and metastatic disease. However, a survival rate describes what happened to a large group of people. It cannot predict exactly what will happen to one person.

Published survival databases may also use categories such as localised, regional, and distant disease rather than numbered cancer stages. Their percentages should not be treated as exact equivalents. Survival statistics are also based on people treated several years earlier and may not fully reflect newer targeted therapies and immunotherapies.

Prognosis may also be influenced by:

• The lung cancer type and subtype
• Whether the tumour can be removed completely
• The number and pattern of involved lymph nodes
• Molecular features, including certain gene alterations
• The availability of an appropriate targeted treatment
• Response to systemic treatment
• Lung function and overall health
• Whether the cancer returns after treatment

A healthcare professional who has reviewed the imaging, pathology and biomarker results can provide more relevant information about an individual’s prognosis.

Thoracic Surgical Assessment at Neumark

Neumark Lung & Chest Surgery Centre specialises in minimally invasive thoracic surgery with a multidisciplinary approach led by Dr Harish Mithiran, senior consultant thoracic surgeon at Gleneagles and Mount Alvernia hospitals.

A thoracic surgical assessment may be appropriate when staging suggests potentially resectable lung cancer, lymph node involvement needs further evaluation or the multidisciplinary team is considering surgery as one part of combined treatment.

Patients can contact Neumark to discuss whether a thoracic surgical assessment is appropriate.