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TNM and number stages of bowel cancer

Men and women discussing bowel cancer

This page tells you about bowel cancer staging using the TNM and number staging systems. You can find the following information

 

A quick guide to what's on this page

TNM and number stages of bowel cancer

The stage of a cancer means how big it is and whether it has spread. TNM stages or the number stages of bowel cancer are used across the world. TNM stands for Tumour, Node, Metastasis. It describes the size of the tumour (T), whether there are cancer cells in the lymph nodes (N) and if the cancer has spread anywhere else in the body (M). In the UK doctors use the 5th version of the TNM bowel cancer staging system. Some doctors use the Dukes' staging system which is described on the next page.

There are 5 main number stages, from stage 0 to stage 4. Stage 0 means the cancer cells are contained within the inner lining of the bowel. It is also called carcinoma in situ.

  • Stage 1 means the cancer has grown through the inner lining of the bowel and may have grown into the muscle wall.
  • Stage 2 means the cancer has grown into the outer covering of the bowel wall. Or the cancer may have grown through the bowel wall into tissues or organs nearby
  • Stage 3 means the cancer has spread into nearby lymph nodes
  • Stage 4 means the cancer has spread to another part of the body, such as the liver or lungs. This is also called advanced bowel cancer.

Doctors also consider the grade of a cancer when deciding on treatment. Grade means how normal or abnormal the cancer cells are when looked at under the microscope. It gives doctors an idea of how a cancer is likely to behave. Low grade cancers tend to be slower growing and are less likely to spread than high grade cancers.
 

CR PDF Icon You can view and print the quick guides for all the pages in the treating bowel cancer section.

 

 

What staging is

The stage of a cancer means how big it is and whether it has spread. The tests and scans you have when diagnosing your cancer give some information about the stage. It is important because treatment is often based on the stage of a cancer. 

It may not be possible to stage the cancer properly until after your operation. But the scans will give your doctor an idea of the stage, and sometimes a decision can be made about giving treatment before surgery.

Many doctors in the UK now use the 5th version of the TNM stages or the number stages of bowel cancer. These stages are used across the world. Some doctors use the Dukes' staging system, which is described on the next page.

 

TNM staging of bowel cancer

TNM stands for Tumour, Node, Metastases. This staging system describes the size of a primary tumour (T), whether any lymph nodes contain cancer cells (N), and whether the cancer has spread to another part of the body (M).

There are 4 stages of tumour size in bowel cancer

  • T1 means the tumour is only in the inner layer of the bowel
  • T2 means the tumour has grown into the muscle layer of the bowel wall
  • T3 means the tumour has grown into the outer lining of the bowel wall
  • T4 means the tumour has grown through the outer lining of the bowel wall. It may have grown into another part of the bowel, or other nearby organs or structures. Or it may have broken through the membrane covering the outside of the bowel (the peritoneum)

Diagram showing T stages of bowel cancer

There are 3 possible stages describing whether cancer cells are in the lymph nodes

  • N0 means there are no lymph nodes containing cancer cells
  • N1 means that 1 to 3 lymph nodes close to the bowel contain cancer cells
  • N2 means there are cancer cells in 4 or more nearby lymph nodes

There are 2 stages of cancer spread (metastasis)

  • M0 means the cancer has not spread to other organs
  • M1 means the cancer has spread to other parts of the body
 

Number stages of bowel cancer

The number system uses the TNM stages to group bowel cancers. There are 5 main stages in this system. They are

Stage 0 or carcinoma in situ (CIS)

If you are told you have CIS or stage 0 colorectal cancer, there are cancer cells in your inner bowel lining. But all the cancer cells are contained within this lining. So there is very little risk of any cancer cells having spread.

Stage 1

This means the cancer has grown through the inner lining of the bowel, or into the muscle wall, but no further. There is no cancer in the lymph nodes (T1, N0, M0 or T2, N0, M0).

Stage 2

This stage is divided into 2a and 2b

  • Stage 2a means that the cancer has grown into the outer covering of the bowel wall, but there are no cancer cells in the lymph nodes (T3, N0, M0)
  • Stage 2b means that the cancer has grown through the outer covering of the bowel wall and into tissues or organs next to the bowel (T4). But no lymph nodes are affected (N0) and the cancer has not spread to another area of the body (M0).

Stage 3

Stage 3 is divided into 3 stages

  • Stage 3a means that the cancer is still in the inner layer of the bowel wall or has grown into the muscle layer, and between 1 and 3 nearby lymph nodes contain cancer cells (T1, N1, M0 or T2, N1, M0)
  • Stage 3b means that the cancer has grown into the outer lining of the bowel wall or into surrounding body tissues or organs, and between 1 and 3 nearby lymph nodes contain cancer cells (T3, N1, M0 or T4, N1, M0)
  • Stage 3c means that the cancer can be any size, has spread to 4 or more nearby lymph nodes, but there is no cancer spread to any other part of the body (any T, N2, M0)

Stage 4

This means your cancer has spread to other parts of the body (such as the liver or lungs) through the lymphatic system or bloodstream (any T, any N, M1).

 

Grading bowel cancer

As well as the stage of bowel cancer, doctors also consider what the cancer cells look like under the microscope (the grade) when deciding on treatment. The grade tells you how normal or abnormal the cancer cells are.  As a normal cell grows and matures, it becomes more specialised for its role and place in the body. This is called differentiation. A pathologist grades bowel cancer as

  • Grade 1 (low grade) - the cancer cells are well differentiated, which means they look quite similar to normal cells
  • Grade 2 (moderate grade) - the cancer cells are moderately differentiated, which means the cells look more abnormal
  • Grade 3 (high grade) - the cancer cells are poorly differentiated, which means they look very abnormal

The grade gives doctors an idea of how the cancer is likely to behave. A low grade cancer is likely to be slower growing and less likely to spread than high grade cancers.

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Updated: 23 September 2013