Lung Cancer


Lung cancer cells behave differently in every person. They may form one or more tumors in the lung or may metastasize (spread) through the wall of the lung, invading other tissues or forming tumors in other organs. Staging will determine the extent of cancer within your body and how far it may have progressed from where it began. Knowing this valuable information enables your doctor to understand more about your type of cancer and create a treatment plan that is most effective for you.

Many things are considered when determining the stage, including the results of the following:

  • Physical exam.
  • Laboratory tests of your blood, urine and body fluids.
  • Imaging studies. A positron emission tomography (PET), computed tomography (CT) of the chest and magnetic resonance imaging (MRI) of the brain are routine.
  • Tissue biopsy. Some biopsies are performed with a needle, although certain situations require that part or all of the tumor be removed surgically to determine a diagnosis.
  • Biomarker and molecular testing.

Because targeting a tumor’s genetic or molecular abnormalities is crucial to the diagnosis and treatment of lung cancer, your doctor may consult with a pathologist, a doctor trained in identifying diseases by studying cells and tissues under a microscope. Your pathology report will describe the results of tissue sample testing and may include results from biomarker testing, tumor molecular analysis or other tests. Ask your doctor to explain how the findings will affect your treatment options. You can request a copy of the report for your records.

Sometimes it is necessary to restage a cancer, such as when it recurs or if the effectiveness of treatment needs to be checked. In this case, some of the original tests used to stage your cancer may be repeated.

Lung Cancer Staging System

A staging system is a way of grouping lung cancers by the way they grow and spread.

The TNM (tumor, node, metastasis) system, developed by the American Joint Committee on Cancer (AJCC) and the International Association for the Study of Lung Cancer, is used to classify and stage lung cancer (see Table 1).

The T category identifies the primary tumor’s size and location. The N category indicates whether lymph nodes show evidence of cancer cells. If so, the location of these lymph nodes is important because it shows how far the disease has progressed. The M category describes distant metastasis (spread), if any. Cancer can spread by growing into nearby tissue, traveling through lymph vessels or blood vessels to other parts of the body. An M subcategory may be added based on the presence of tumor cells that can be detected only by using a microscope or molecular testing. For illustration purposes, the tumors in Figure 1 below are shown on one side of the lungs. They may, however, be present in any area of the lungs.

Staging non-small cell lung cancer (NSCLC) begins with combining the patient’s T, N and M status to determine the extent of the cancer. A number is assigned that can range from Stage 0 through Stage IV (see Table 2). Stage 0 is also known as in situ, and it is a precursor of an invasive cancer. Stages I and II are generally confined to the local area where the cancer is found with or without adjacent lymph node involvement. They are treated as early stage and are considered potentially curable; therefore, every effort should be made to render a cure for these diagnoses. Stage III NSCLC is considered locally advanced, still confined to the chest but having spread to regional lymph nodes outside the lung in the mediastinum. Stage IV is locally or regionally advanced disease that has spread to distant sites, such as the brain, liver or bone.

Doctors may use a combined staging approach to stage small cell lung cancer (SCLC), referring to the AJCC TNM classification as well as the Veterans Administration Lung Study Group (VALSG) staging system, which specifies SCLC as limited stage or extensive stage.

Limited-stage SCLC is confined to one part of the chest, in just one part of the lung and in nearby lymph nodes. Limited-stage cancers are Stages I to III.

Extensive-stage SCLC has spread to other parts of the body, such as the area between the lungs, bone, brain or other lung. It is Stage IV and has metastasized to too many areas for radiation therapy to be used with curative intent.

Table 1. Stages of Lung Cancer

Stage TNM classifications
Occult carcinoma TX, N0, M0
0 Tis, N0, M0
IA1 T1mi, N0, M0
T1a, N0, M0
IA2 T1b, N0, M0
IA3 T1c, N0, M0
IB T2a, N0, M0
T2b, N0, M0
T1a or T1b or T1c, N1, M0
T2a or T2b, N1, M0
T3, N0, M0
T1a or T1b or T1c, N2, M0
T2a or T2b, N2, M0
T3, N1, M0
T4, N0 or N1, M0
T1a or T1b or T1c, N3, M0
T2a or T2b, N3, M0
T3, N2, M0
T4, N2, M0
T3, N3, M0
T4, N3, M0
Any T, Any N, M1
Any T, Any N, M1a or M1b
Any T, Any N, M1c

Table 2. AJCC System for Classifying of Lung Cancer

Category Definition
Tumor (T)
TX Primary tumor cannot be assessed, or tumor proven by the presence of malignant (cancerous) cells in sputum (mucus that has been coughed up) or bronchial washings (cells collected from inside the airways) but not visualized by imaging or bronchoscopy.
T0 No evidence of primary tumor.
Tis Carcinoma in situ.
Squamous cell carcinoma in situ (SCIS).
Adenocarcinoma in situ (AIS): adenocarcinoma with pure lepidic pattern (on the alveolar lining), ≯ (not more than) 3cm in greatest dimension.
Tumor ≯ (not more than) 3 cm in greatest dimension, surrounded by lung or visceral pleura (membrane surrounding the lung), without bronchoscopic evidence of invasion more proximal than the lobar bronchus (i.e., not in the main bronchus).
Minimally invasive adenocarcinoma: adenocarcinoma (≯ [not more than] 3 cm in greatest dimension) with a predominantly lepidic pattern (on the alveolar lining) and ≯ (not more than) 5 mm invasion in greatest dimension.
Tumor ≯ (not more than) 1 cm in greatest dimension.
Tumor > (more than) 1 cm but ≯ (not more than) 2 cm in greatest dimension.
Tumor > (more than) 2 cm but ≯ (not more than) 3 cm in greatest dimension.
Tumor > (more than) 3 cm but ≯ (not more than) 5 cm or having any of the following features:
    • Involves the main bronchus regardless of distance to the carina (ridge at the base
      of the trachea), but without involvement of the carina.
    • Invades visceral pleura (membrane surrounding the lung).
    • Associated with atelectasis (collapse of part of the lung) or obstructive pneumonitis
      (inflammation of lung tissues) that extends to the hilar region, involving part or all
      of the lung.
Tumor > (more than) 3 cm but ≯ (not more than) 4 cm in greatest dimension.
Tumor > (more than) 4 cm but ≯ (not more than) 5 cm in greatest dimension.
T3 Tumor > (more than) 5 cm but ≯ (not more than) 7 cm in greatest dimension or directly invading any of the following: parietal pleura (outer lung membrane), chest wall (including superior sulcus tumors), phrenic nerve (nerve that helps control breathing), parietal pericardium; or separate tumor nodule(s) in the same lobe as the primary.
T4 Tumor > (more than) 7 cm or tumor of any size invading one or more of the following: diaphragm, mediastinum (area between the lungs), heart, great vessels, trachea (windpipe), recurrent laryngeal nerve (nerve that helps speech), esophagus, vertebral body, or carina (at base of the trachea); separate tumor nodule(s) in an ipsilateral lobe (lobe that is on the same side of the body) different from that of the primary.
Node (N)
NX Regional lymph nodes cannot be assessed.
N0 No regional lymph node metastasis.
N1 Metastasis in ipsilateral (on the same side) peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes, including involvement by direct extension.
N2 Metastasis in ipsilateral (on the same side) mediastinal and/or subcarinal lymph node(s).
N3 Metastasis in contralateral (on the opposite side) mediastinal, contralateral hilar, ipsilateral (on the same side) or contralateral scalene, or supraclavicular lymph node(s) (located above the collarbone).
Metastasis (M)
M0 No distant metastasis.
Distant metastasis.
Separate tumor nodule(s) in a contralateral (on the opposite side) lobe; tumor with pleural or pericardial nodules or malignant pleural or pericardial effusion.
Single extrathoracic (outside of the lung) metastasis in a single organ (including involvement of a single nonregional node).
Multiple extrathoracic (outside of the lung) metastases in a single organ or in multiple organs.

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.