Staging and grading

After being diagnosed with stomach cancer, you have further tests to see whether the cancer has spread. Your doctors can use these tests to help work out the stage of the cancer. The exact stage is only known after surgery to remove the cancer. Knowing the stage helps you and your doctors decide on the most appropriate treatment for you.

The stage of a cancer describes its size and whether it has spread. Doctors usually stage cancer of the stomach using the TNM system or the number system.

T refers to the size and spread of the tumour, N to whether or not nearby lymph nodes have cancer cells in them, and M to whether the cancer has spread to other parts of the body.

The number system uses stages 1–4. Stage 1 is early stomach cancer and stage 4 is advanced stomach cancer.

The grade is how the cancer cells look under a microscope. It gives an idea of how quickly the cancer may develop. For example, stomach cancer can be slow growing (low-grade) or fast growing (high-grade).

Staging

The stage describes how far the cancer has grown from where it started and if it has spread anywhere else.

Knowing the stage is important. It affects the decisions you and your doctors make about the treatment you have.

It’s only possible to tell the exact stage of the cancer after an operation to remove it.

There are two main ways that stomach cancer is staged: the TNM system and the number system.

TNM staging system

The most commonly used staging system for stomach cancer is the TNM staging system:

T refers to the size and spread of the tumour. This will be a number between 0 and 4 depending on the size and spread of the tumour.

N refers to whether nearby lymph nodes have cancer cells in them. This will be a number between 0 and 3 depending on how many lymph nodes contain cancer cells.

M refers to whether the cancer has spread to other parts of the body (secondary or metastatic cancer). The M stage will be 0 if it hasn’t spread and 1 if it has.

As an example, a cancer may be described as T3 N2 M0.

Number staging system

This describes the stage of stomach cancer with a number ranging from 1–4.

Stage 1

The cancer is only in the lining of the stomach (mucosa) and may have spread to 1–2 lymph nodes.

OR

The cancer has grown into the muscle layer of the stomach but there is no cancer in the lymph nodes.

Stage 2

The cancer is in the stomach lining (mucosa) and has spread to 3 or more lymph nodes.

OR

The cancer has grown into the muscle layer and has spread into 1–6 lymph nodes.

OR

The cancer has reached the outer stomach layer (serosa) but is only in 1–2 lymph nodes.

OR

The cancer has grown through the stomach wall but hasn’t grown into nearby tissues or spread to the lymph nodes.

Doctors sometimes call stages 1 and 2 early stomach cancer.

Stage 3

The cancer has grown into the muscle layer and has spread into 7 or more lymph nodes.

OR

The cancer has reached the outer stomach layer (serosa) and has spread into 3 or more lymph nodes.

OR

The cancer has grown through the stomach wall. It has also spread into lymph nodes and/or into nearby tissues such as the liver or gullet or abdominal wall

Doctors call stage 3 locally advanced stomach cancer.

Stage 4

The cancer has spread outside the stomach to other parts of the body, such as the lungs or bones.

Doctors usually call stage 4 advanced or metastatic stomach cancer.


Grading

Grading is about how the cancer cells look under the microscope compared with normal cells. The grade helps your doctor to decide if you need further treatment after surgery.

  • Grade 1 or low-grade or well differentiated - The cancer cells look similar to normal cells and usually grow slowly and are less likely to spread.
  • Grade 2 or moderate-or intermediate-grade - The cancer cells look more abnormal and are slightly faster growing.
  • Grade 3 or high-grade or poorly differentiated - The cancer cells look very different from normal cells and may grow more quickly.

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