What does the stage of a cancer mean?

The stage of a cancer is how much and how far it has spread in your body. Your healthcare provider uses exams and tests to find out the size of the cancer and where it is.

Some tests such as CT scans can also show if the cancer has spread to nearby areas, and if it has spread to other parts of your body. The stage of a cancer is one of the most important things to know when deciding on treatment.

The place where cancer starts is called the primary site. Stomach cancer can spread from the primary site (in the stomach) to other parts of your body. Cancer that has spread is called metastatic cancer. When a cancer spreads, it’s said to have metastasized.

To better understand staging, it helps to know the names of the layers that make up the stomach wall. From the inside to the outside, the layers are:

• Mucosa (the innermost lining)

• Submucosa (layer has connective tissue, blood vessels, and nerve cells)

• Muscularis propria (the muscle layer)

• Subserosa

• Serosa (the lining that covers the outside of the stomach)

Stomach cancer starts in the inner lining, or mucosa, of the stomach. As it grows, it can grow through (invade) the layers of the wall of the stomach. Then it can spread (metastasize) to other parts of the body.

The TNM system for stomach cancer

The most commonly used system to stage stomach cancer is the TNM system from the American Joint Committee on Cancer (AJCC). Staging is very complex. Be sure to ask your healthcare provider to explain the stage of your cancer to you in a way you can understand.

The first step is to find the value for each part of the TNM system. Here's what the letters stand for in the TNM system:

• T tells how far the primary tumor has spread through the layers of the stomach wall and into nearby structures (tissues).

• N tells if the lymph nodes near the primary tumor have cancer in them.

• M tells if the cancer has spread ( metastasized) to distant organs, lymph nodes, and structures in the body, like the liver, lungs, diaphragm, or lining of your belly or abdomen (called the peritoneum).

Numbers or letters after T, N, and M provide more details about each of these factors. There are also two other values that can be assigned:

• X means the healthcare provider does not have enough information to tell the extent of the primary tumor, or if the lymph nodes have cancer cells in them.

• 0 means no sign, such as no sign of cancer in lymph nodes (N0).

What are the stage groupings of stomach cancer?

The T, N, and M values from the TNM system are used to put these cancers into stage groupings. These groupings give an overall description of your cancer. A stage grouping can have a value of 0 or Roman numerals I (1), II (2), III (3), or IV (4). The higher the number, the more advanced your cancer is. Staging can be done at different times. Clinical staging is the stage based on the results of physical exams, imaging tests, procedures, and biopsies. The clinical stage is before treatment. Pathological staging is the stage based on the results of exams or tests and results from stomach surgery. It can be different than the clinical stage. It's important for your healthcare provider to explain your stage to you in a way you can understand.

These are the pathological stage groupings of stomach cancer and what they mean:

Stage 0 (also called carcinoma in situ). Very abnormal-looking cells (called high-grade dysplasia) that will likely become cancer or cancer are found, but only in the first layer of the mucosa (epithelium). The stage grouping is Tis, N0, M0.

Stage I. The cancer has not spread to distant organs or structures (tissues). But it has grown in one of these ways:

• Stage IA. The cancer has grown from the top layer of mucosa (epithelium) deeper into the stomach wall to the next layers of mucosa or into the submucosa layer under the mucosa. But it's not in the lymph nodes. The stage grouping is T1, N0, M0.

• Stage IB. This stage can be either of these:

  • The cancer has grown from the top layer of mucosa (epithelium) into the next layers of the mucosa or into the submucosa layer. It has spread to 1 or 2 nearby lymph nodes. The stage grouping is T1, N1, M0.

  • The cancer has grown into the muscle layer of the stomach (the muscularis propria). But it has not spread to lymph nodes. The stage grouping is T2, N0, M0.

Stage II. The cancer has not spread to distant organs or structures. But it has grown in one of these ways:

• Stage IIA. This stage can be any of these:

  • The cancer has grown from the top layer of mucosa (epithelium) into the next layers of mucosa or into the submucosa layer. It has spread to 3 to 6 nearby lymph nodes. The stage grouping is T1, N2, M0.

  • The cancer has spread to the muscle layer of the stomach (muscularis propria) and has spread to 1 or 2 nearby lymph nodes. The stage grouping is T2, N1, M0.

  • The cancer has spread through all the layers of the stomach but not through the lining outside the stomach (the serosa). It has not spread to lymph nodes. The stage grouping is T3, N0, M0.

• Stage IIB. This stage can be any of these:

  • The cancer has grown into the submucosa and has spread to 7 to 15 nearby lymph nodes. The stage grouping is T1, N3a, M0.

  • The cancer has grown into the muscle layer of the stomach (the muscularis propria) and has spread to 3 to 6 nearby lymph nodes. The stage grouping is T2, N2, M0.

  • The cancer has gone through all the layers of the stomach, but not through the lining outside the stomach (the serosa). It has spread to 1 or 2 nearby lymph nodes. The stage grouping is T3, N1, M0.

  • The cancer has grown through all the layers of the stomach, including the outer layer (the serosa). But it’s not in nearby lymph nodes or other organs or tissues. The stage grouping is T4a, N0, M0.

Stage III. The cancer is not in distant organs and has grown in one of these ways:

• Stage IIIA. This stage can be any of these:

  • The cancer has grown into the muscle layer of the stomach (the muscularis propria) and has spread to 7 to 15 nearby lymph nodes. The stage grouping is T2, N3a, M0.

  • The cancer has grown through the layers of the stomach but not through the lining outside the stomach (the serosa). It has spread to 3 to 6 nearby lymph nodes. The stage grouping is T3, N2, M0.

  • The cancer has grown through all the layers of the stomach and is in the serosa or the lining of your belly (called the peritoneum). It's in 1 to 6 nearby lymph nodes, but it’s not in any other nearby organs or tissues. The stage grouping is T4a, N1 or N2, M0.

  • The cancer has gone through all the layers of the stomach, including the serosa, and into nearby organs and tissues (like the intestines, spleen, liver, or kidney). It has not spread to nearby lymph nodes. The stage grouping is T4b, N1, M0.

• Stage IIIB. This stage can be any of these:

  • The cancer has grown through the inside layers as far as the muscle layer (muscularis propria) of the stomach and has spread to 16 or more nearby lymph nodes. The stage grouping is T1 or T2 N3b M0.

  • The cancer has grown into the subserosa layer of the stomach but not the serosa. It has spread to 7 to 15 nearby lymph nodes. The stage grouping is T3, N3a, M0.

  • The cancer has gone through all the layers of the stomach and is in the outer layer (the serosa). It's in 7 to 15 nearby lymph nodes, but it’s not in any other nearby organs or tissues. The stage grouping is T4a, N3a, M0.

  • The cancer has gone through all the layers of the stomach and into nearby organs and tissues (like the intestines, spleen, liver, diaphragm, or kidney). It has spread to 1 to 6 nearby lymph nodes. The stage grouping is T4b, N1 or N2, M0.

• Stage IIIC. This stage can be any of these:

  • The cancer has grown into the subserosa layer but not as far as the serosa layer of the stomach. It has spread to 16 or more nearby lymph nodes, but it’s not in any other nearby organs or tissues. The stage grouping is T3, N3b, M0.

  • The cancer has gone through all the layers of the stomach and is in the outer layer (the serosa). It has spread to 16 or more nearby lymph nodes, but it's not in any other nearby organs or tissues. The stage grouping is T4a, N3b, M0.

  • The cancer has gone through all the layers of the stomach, including the serosa, and into nearby organs and tissues (like the intestines, spleen, liver, diaphragm, or kidney). It has spread to 7 or more nearby lymph nodes. The stage grouping is T4b, N3a or N3b, M0.

Stage IV. The cancer has grown into any layers of the stomach and might have spread to nearby tissues. It may or may not have spread to lymph nodes. It has spread beyond the stomach to distant parts of the body, such as the lungs, liver, or brain. The stage grouping is Any T, Any N, M1.

Talking with your healthcare provider

Once your cancer is staged, talk with your healthcare provider about what the stage means for you. Ask any questions and talk about your concerns.