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, according to the American Cancer Society. The two main types of lung cancer are non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Overall, NSCLC accounts for 80 percent to 85 percent of cases and SCLC for 10 percent to 15 percent.

NSCLC and SCLC are classified using different lung cancer staging systems. In both cases, the stage of cancer can help determine the best treatment options. Your doctor may need to biopsy your tumor to determine its type and stage. This involves taking a tissue sample to be examined under a microscope.

How Is Non-Small Cell Lung Cancer Staged?

The American Joint Committee on Cancer (AJCC) TNM system is the standard staging system for NSCLC. The TNM staging system considers 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 factor. 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, doctors go through a process called stage grouping. This information is used to help predict the course of disease and develop lung cancer treatment plans.

Non-Small Cell Lung Cancer Stages

NSCLC staging begins at stage 0 (also called carcinoma in situ). The other stages, which are sometimes written using Roman numerals, range from stage 1 (stage I) through stage 4 (stage IV). NSCLC staging can be complicated. Don’t be afraid to ask your oncology team to explain it if you’re confused.

Occult (Hidden) Cancer

When cancer cells have been found in a sample of mucus or in other lung fluids, but the primary tumor can’t 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’s no sign of cancer spread to neighboring lymph nodes or distant organs.

Stage 1 NSCLC

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

Stage 1A

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

Stage 1B

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

• It’s more than 3 centimeters but less than 4 centimeters across.
• It has grown into the membranes covering the lungs and is no more than 4 centimeters across.
• It has grown into the main airway and is more than 2 centimeters away from the point where the trachea (windpipe) splits, and it’s no more than 4 centimeters across.
• It has partially clogged the airways, and it’s no more than 4 centimeters across.

There’s no sign of cancer spread to neighboring lymph nodes or distant organs.

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’s more than 4 centimeters but less than 5 centimeters across.
• It has grown into the membranes covering the lungs.
• It has grown into the main airway, and it’s more than 2 centimeters away from where the trachea splits.
• It has partially clogged the airways.

There’s no sign of cancer spread to neighboring lymph nodes or distant organs.

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’s no sign of cancer spread to neighboring lymph nodes or distant organs.

Stage 3 NSCLC

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

• Tumor size
• Presence of more than one tumor
• 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 main airway. There’s no sign of cancer spread to other areas of the body.

Stage 4 NSCLC

Stage 4 NSCLC indicates that cancer has spread beyond the lungs, so there’s more extensive disease.

Stage 4A

This stage can be broken down into two substages, defined by how much the cancer has spread (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 (malignant pleural effusion).

M1b is defined by a spread that forms a single tumor outside 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).

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. Although the TNM system can be applied to SCLC, it’s not widely used or as important as the two-stage method.

Limited Stage

Limited-stage SCLC means the cancer is present on just one side of the chest and can be treated using radiation. Generally, this includes cancers that are in just 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 and in the center of the chest.

Limited-stage SCLC is defined by the fact that the cancer is restricted to an area small enough to get radiation in only one treatment area (also called the treatment “port” or “field”). About 1 in 3 people diagnosed with SCLC have limited-stage cancer when it’s 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 3 people diagnosed with SCLC have extensive-stage cancer when it’s first discovered.

Talk With Others Who Understand

MyLungCancerTeam is the social network for people with lung cancer and their loved ones. On MyLungCancerTeam, more than 13,000 members come together to ask questions, give advice, and share their stories with others who understand life with lung cancer.

Are you wondering how staging works with lung cancer? Do you have questions about others’ experiences with staging? Share your thoughts in the comments below, or start a conversation by posting on your Activities page.