Staging and grading

If you’ve been diagnosed with stomach cancer, you will 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 to 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 of a cancer describes how far the cancer has grown from where it started, and whether 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 stomach cancer after an operation to remove it. There are two staging systems.

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: 

  • T1 – the tumour has grown into the inner wall (mucosa or submucosa) of the stomach
  • T2 – the tumour has grown into the muscle layer of the stomach
  • T3 – the tumour has grown into the outer lining of the stomach
  • T4 – the tumour has grown through the outer lining of the stomach.

N refers to whether nearby lymph nodes have cancer cells in them:

  • N0 – no lymph nodes contain cancer cells
  • N1 – cancer cells are in 1 to 2 nearby lymph nodes
  • N2 – cancer cells are in 3 to 6 nearby lymph nodes
  • N3 – cancer cells are in 7 or more nearby lymph nodes.

M refers to whether the cancer has spread to other parts of the body (secondary or metastatic cancer): 

  • M0 – the cancer has not spread 
  • M1 – the cancer has spread to other parts of the body.

Number staging system

This is a different staging system that has just four stages. These can be described as follows:

Stage 1

The cancer is in the lining of the stomach (mucosa) and may have reached the muscle layer. Between 0 to 3 lymph nodes may be involved.

Stage 2

The cancer is contained within the stomach wall and up to 6 lymph nodes are involved, or the cancer has grown through the stomach wall but no lymph nodes or other organs are involved.

Doctors sometimes call stages 1 and 2 early stomach cancer.

Stage 3

The cancer is contained within the stomach wall and more than 6 lymph nodes are involved. Or the cancer has grown through the stomach wall and up to 6 lymph nodes are involved.

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, liver or the bones.

Doctors usually call stage 4 advanced or metastatic stomach cancer.


An overview of staging stomach cancer

Number/TNM stage

Stage 1

  • T1, N0, M0 The cancer is in the lining of the stomach.
  • T1, N1, M0 The cancer is in the lining of the stomach and has spread to 1 to 2 lymph nodes.

Stage 2

  • T1, N2, M0 The cancer is in the stomach lining (mucosa) and has spread to 3 or more lymph nodes.
  • T2, N1, M0 or T2, N2, M0 The cancer has grown into the muscle layer and spread into 1 to 6 lymph nodes.
  • T3, N1, M0 The cancer has reached the outer stomach layer and in 1 to 2 lymph nodes.
  • T4, N0, M0 The cancer has grown through the stomach wall but hasn’t grown into nearby tissues or spread to the lymph nodes.

Stage 3

  • T2, N3, M0 The cancer has grown into the muscle layer and has spread into 7 or more lymph nodes.
  • T3, N2, M0 or T3, N3, M0 The cancer has reached the outer stomach layer (serosa) and has spread into 3 or more lymph nodes.
  • T4, N1, M0 or T4, N2, M0 The cancer has grown through the stomach wall, spread into lymph nodes and/or into nearby tissues.

Stage 4

  • any T, any N, M1 The cancer has spread outside the stomach to other parts of the body.


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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