Staging and grading
Staging a cancer involves describing its size, where it is and whether it has spread. Knowing the stage of your cancer will help you and your doctor decide on the best treatment.
If you have surgery, your doctor will grade the cancer by looking at how normal or abnormal the cells look under a microscope. Grading the cancer can help to show how likely it is to spread and how quickly.
The most common staging system is the TNM system. You may also hear about the Dukes’ system which is explained below.
- T (tumour) - how far the tumour has grown through the bowel wall
- N (nodes) - whether the cancer has spread to nearby lymph nodes
- M (metastases) - whether the cancer has spread (metastasised) to other parts of the body
- T1 - the tumour is in the inner layer of the bowel
- T2 – the tumour has grown into the muscle layer of the bowel wall
- T3 – the tumour has grown into the outer lining of the bowel wall
- T4 – the tumour has grown through the outer lining of the bowel wall
- N0 – no lymph nodes contain cancer cells
- N1 – cancer cells in up to three nearby lymph nodes
- N2 – cancer cells in four or more nearby lymph nodes
- M0 – the cancer hasn’t spread to other parts of the body
- M1 – the cancer has spread to other parts of the body, like the liver or lungs
You will sometimes see the TNM staging report written with a lower case letter in front of it
- cTNM means the report is based on the clinical findings on scans and biopsies before the start of treatment
- pTNM means the report is based on the full findings of both the pre-treatment investigations and confirmed by a pathological assessment (of tissue under the microscope) following surgery
Doctors sometimes use this system to describe the stage of the cancer. The list below shows how the Dukes’ system compares to the TNM system.
- TNM stage 1
- T1, N0, M0 or T2, N0, M0
The cancer has grown into the inner layer or muscle layer of the bowel wall. It has not spread to the lymph nodes or other parts of the body.
- TNM stage 2
- T3, N0, M0 or T4, N0, M0
The cancer has grown through the muscle layer or outer layer. It may be growing into tissues near the bowel but has not spread to the lymph nodes or other parts of the body.
- TNM stage 3
- Any T, N1 or N2, M0
The cancer is any size and has spread to nearby lymph nodes. It has not spread to other parts of the body.
- TNM stage 4
- Any T, any N, M1
The cancer is any size. It may or may not have spread to nearby lymph nodes but it has spread to other parts of the body, like the liver or lungs.
Grading the cancer helps you and your doctor understand how quickly it may grow and spread. A low grade cancer may grow more slowly and is less likely to spread than a high grade cancer.
- Grade 1 (low grade) - the cancer cells look similar to normal cells (well differentiated)
- Grade 2 (moderate grade) – the cancer cells look more abnormal (moderately differentiated)
- Grade 3 (high grade) – the cancer cells look very abnormal (poorly differentiated)
Updated August 2018. Due for review March 2019