When someone is first diagnosed with lung cancer, doctors will determine the stage of the cancer. According to the American Cancer Society, “Staging is the process of finding out how much cancer is in a person’s body and where it’s located.”

Lung cancer is the second most common cancer in both men and women in the United States. The two main types of lung cancer are non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Overall, NSCLC accounts for 84 percent of cases and SCLC for 13 percent.

NSCLC and SCLC are classified using different lung cancer staging systems. In both cases, the stage of cancer can help determine the appropriate treatment options.

How Is Non-Small Cell Lung Cancer Staged?

The American Joint Committee on Cancer (AJCC) TNM system is the standard staging system for NSCLC. TNM staging takes into consideration three important pieces of information:

• Tumor (T) — How large is the main tumor? What is the extent of its growth?
• Lymph nodes (N) — Has the cancer spread to any nearby lymph nodes?
• Metastasis (M) — Has the cancer spread to any other organs, like the brain, bones, liver, adrenal glands, or the other lung?

The TNM system also uses numbers and letters to provide a little more information about each of the factors. The higher the number, the more advanced the cancer. Within a stage, an earlier letter signifies a lower stage. For example, stage 1A1 is lower than stage 1A2.

After the T, N, and M categories have been determined, stage grouping is then performed to assign the cancer’s overall stage. This information is used to help predict the course of disease and develop lung cancer treatment plans.

The Stages of Non-Small Cell Lung Cancer

NSCLC staging begins at stage 0 (also called carcinoma in situ). The other stages range from stage 1 (stage I) through stage 4 (stage IV). Roman numerals are sometimes used for stage numbers. NSCLC staging can be complicated. Don’t be afraid to ask your doctor to explain it in an understandable way if you’re confused.

Occult (Hidden) Cancer

When cancer cells have been found in a sample of sputum (mucus) or in other lung fluids, but the primary tumor cannot be located, the cancer is said to be occult. This stage assumes the cancer has not spread to neighboring lymph nodes or distant organs in the body.

Stage 0 NSCLC

In stage 0, the tumor is present only in the top layers of cells that line the air passages and has not spread deeper into other lung tissues. There is no sign of cancer spread to neighboring lymph nodes or distant organs in the body.

Stage 1 NSCLC

Stage 1 NSCLC can be split into stage 1A and stage 1B, which can be further subdivided.

Stage 1A

In stage 1A, the tumor is classified as a minimally invasive adenocarcinoma. There are three substages: stage 1A1, 1A2, and 1A3. These are differentiated by the location of the tumor, its size, and its depth within the lung. There is no sign of cancer spread to neighboring lymph nodes or distant organs in the body.

Stage 1B

At stage 1B, the tumor exhibits one or more of the following features:

• It is larger than 3 centimeters but smaller than 4 centimeters across.
• It has grown into the membranes covering the lungs (visceral pleura), and it is not larger than 4 centimeters across.
• It has grown into the main airway (bronchus) and is more than 2 centimeters away from the point where the trachea splits (carina), and it is not larger than 4 centimeters across.
• It has partially clogged the airways, and it is not larger than 4 centimeters across.

There is no sign of cancer spread to neighboring lymph nodes or distant organs in the body.

Read more about stage 1 lung cancer.

Stage 2 NSCLC

Stage 2 NSCLC is also split into two categories. The main differentiating factor is tumor size.

Stage 2A

A stage 2A tumor exhibits one or more of the following features:

• It is larger than 4 centimeters across, but it is smaller than 5 centimeters across.
• It has grown into the visceral pleura. Its size is between 4 and 5 centimeters across.
• It has grown into the bronchus, and it is more than 2 centimeters away from the carina. Its size is between 4 and 5 centimeters across.
• It has partially clogged the airways, and it is between 4 and 5 centimeters across.

There is no sign of cancer spread to neighboring lymph nodes or distant organs in the body.

Stage 2B

Within stage 2B of NSCLC, there are many factors to consider, including:

• Tumor size
• The extent of spread to lymph nodes within the lung
• Invasion into other parts of the lung, chest wall, or surrounding organs

There is no sign of cancer spread to neighboring lymph nodes or distant organs in the body.

Read more about stage 2 lung cancer.

Stage 3 NSCLC

Within stage 3 of NSCLC, there are many different combinations of factors, such as:

• Tumor size
• If there is more than one tumor present
• The extent of spread to lymph nodes within the lung
• Invasion into other parts of the lung, chest wall, or surrounding organs

The cancer may have spread to lymph nodes within the lung or near the bronchus. There is no sign of cancer spread to distant organs in the body.

Read more about stage 3 lung cancer.

Stage 4 NSCLC

Stage 4 NSCLC indicates that cancer has spread beyond the lungs.

Stage 4A

This stage can be broken down into two different substages, defined by the extent of metastasis (M1a or M1b). The tumor can be any size and may or may not have spread to nearby structures or into neighboring lymph nodes.

In the case of M1a, any of the following must be true:

• The cancer has spread into the other lung.
• Cancer cells are found in the fluid surrounding the heart (known as a malignant pericardial effusion).
• Cancer cells are found in the fluid surrounding the lung (known as a malignant pleural effusion).

M1b is defined by a spread that forms a single tumor outside of the chest, in distant lymph nodes or organs (such as the brain, liver, or bones).

Stage 4B

A stage 4B tumor can be any size and may or may not have spread to nearby structures or into neighboring lymph nodes. It has metastasized to make more than one tumor outside the chest (in distant lymph nodes or other organs).

Read more about stage 4 lung cancer.

How Is Small Cell Lung Cancer Staged?

Unlike NSCLC, the most common method of staging SCLC uses only two stages: limited stage and extensive stage. While the TNM system can be applied to SCLC, it is not widely used or as important as the two-stage method.

Limited Stage

Limited stage SCLC means the cancer is present on only one side of the chest and can be treated using radiation. Generally, this includes cancers that are in only one lung (unless the tumors have spread throughout the lung). The cancer may also have spread to the lymph nodes on the same side of the chest.

Depending on the location of the lymph nodes, some cancers may still be considered limited stage. This includes lymph nodes above the collarbone (supraclavicular nodes) and in the center of the chest (mediastinal lymph nodes).

Limited stage SCLC is defined by the fact that the cancer is restricted to an area small enough to treat it with only one treatment area or “port.” About 1 in every 3 people diagnosed with SCLC have limited stage cancer when it is first discovered.

Extensive Stage

Extensive stage SCLC refers to cancer that is widespread throughout both lungs. It may have also moved into lymph nodes on the other side of the chest or to other parts of the body (such as the bone marrow). SCLC that has spread into the fluid surrounding the lungs may also be classified as extensive stage. Roughly 2 in every 3 people diagnosed with SCLC have extensive stage cancer when it is first discovered.

Lung Cancer Condition Guide

• Lung Cancer — An Overview
• Symptoms of Lung Cancer
• Treatments for Lung Cancer
• Types of Lung Cancer
• Conditions Related To Lung Cancer
• What Causes Lung Cancer?
• How Is Lung Cancer Diagnosed?