Staging and grading of colon and rectal cancer

Staging Back to top

The stage of a cancer describes its size and whether it has spread beyond its original site. Knowing the stage of your cancer helps doctors decide on the best treatment for you. The most commonly used staging system used is the TNM system:

• T refers to the size of the tumour
• N refers to whether the cancer has spread to the lymph nodes (sometimes called glands)
• M is whether the cancer has spread to other parts of the body (secondary or metastatic cancer).

Information from the TNM system is grouped together into an overall number stage (stages 1-4).

Stage 1

The cancer has not spread beyond the original tumour.

Stage 2

Tumours may have grown through the bowel wall and into nearby tissues, but have not spread to new parts of the body.

Stage 3

Tumour cells can be found in nearby lymph nodes.

Stage 4

The tumour has spread to other parts of the body.

There are other staging systems used to stage colon and rectal cancer. The first system, called the Dukes staging system, is being replaced by the TNM staging system. Some doctors might still talk about the Dukes system. However, the TNM staging system is now widely accepted and gives more detailed information.  

Grading Back to top

Doctors will look at a sample of the cancer cells under a microscope to find the grade of your cancer. It may be graded as:

Grade 1 (low-grade)

The cancer cells tend to grow slowly, look quite similar to normal cells (are ‘well differentiated’) and are less likely to spread than higher grades.

Grade 2 (moderate-grade) 

The cells look more abnormal and are growing slightly quicker.

Grade 3 (high-grade)

The cancer cells tend to be growing more quickly, look very abnormal (are ‘poorly differentiated’) and are more likely to spread than low-grade cancers.