Cancer staging and grading

Published by Bupa's Health Information Team, June 2010.

This factsheet is for people who would like information about the main ways of staging and grading cancer.

Cancer develops when the cells of the body change and grow in an uncontrolled way. Doctors and surgeons stage and grade cancer to describe the size of the tumour and how far and fast it's growing. It's important because it can help determine what the best course of treatment is.

How cancer develops

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About cancer

A cancerous (malignant) tumour is a lump of cells in your body that grows in an abnormal and uncontrolled way. Cancerous tumours can grow in one of your organs and spread to other parts of your body through your bloodstream or lymphatic system (part of your immune system). Cancers that spread (metastasise) in this way may form secondary tumours. Non-cancerous tumours that don't invade other tissues or spread to other parts of the body are known as benign.

What is cancer staging and grading?

If your doctor or surgeon suspects you have cancer, you will need to have tests to confirm a diagnosis. The tests will be specific for the type of cancer you may have. At this point, your doctor or surgeon will try to find out the size of your tumour, how far it has grown and the speed at which it may grow. This is called staging and grading and is used to describe solid, cancerous tumours.

Staging is important because it helps your specialist decide what the best treatment is for you, as well as determining the likely course of your cancer.

Staging

Staging is used by doctors and surgeons to describe the size of your tumour and how far it may have spread within your body.

The most commonly used method to describe cancers worldwide is called the TNM staging system.

TNM staging system

Your doctor or surgeon will use the TNM staging system to describe your cancer if you have a solid tumour in your breast, head, neck or lungs, for example. A different staging system may be used for specific types of cancers.

The TNM system describes the size of your original (primary) tumour (T), whether any cancer cells have spread from your primary tumour and have reached nearby lymph nodes (N), and whether the cancer cells have spread further around your body (M). Each stage has numbers that are used to categorise your cancer more specifically.

T in TNM staging
The T in the TNM system stands for tumour. This part of the staging system generally describes the size or growth of your tumour.

• T0 means your doctor or surgeon can't find any evidence of a primary tumour.
• Tis or Cis stand for tumour or cancer in situ. If your cancer is described in this way it means your tumour is in one small area and hasn't spread yet.
• T1 to 4 refers to increasingly advanced cancer stages, for example, T1 means your tumour may be early stage and small, and T4 means it may be advanced and large. Sometimes a and b are also used to define your cancer further - for example, T2a and T2b - and may refer to the tissues that the cancer has spread into, although this will be specific to the type of cancer you have.
• TX may be used if the stage of your cancer isn't clear.

N in TNM staging
The N in the TNM system stands for nodes (or lymph nodes). Your lymph nodes are small, bean-shaped organs that are part of your lymphatic system. This system contains fluid called lymph, which contains cells that fight infection.

Your doctor or surgeon will rate your cancer according to whether or not it has spread to any nearby lymph nodes.

• N0 means there are no cancer cells in nearby lymph nodes.
• N1, N2 and N3 generally refer to either how many lymph nodes your cancer has spread to or the position of the nodes in relation to your primary tumour. The higher the number, the more lymph nodes may be affected.
• NX may be used if the stage of your cancer isn't clear.

If your cancer has spread to your lymph nodes it may mean that it has spread to other areas of your body too. Your doctor or surgeon can't always tell if this has happened, but in this situation he or she will probably suggest you have adjuvant (preventative) treatment. This means you may have chemotherapy, radiation therapy, or hormone therapy alongside you primary treatment to try and kill any cancer cells that may have broken away from your primary tumour.

M in TNM staging
The M in the TNM staging system stands for metastases. If your cancer has metastasised, this means it has spread to other parts of your body. Your doctor or surgeon will rate your cancer according to whether it has spread or not.

• M0 means your cancer has not spread to any other parts of your body.
• M1 means your cancer has spread away from your primary tumour and into one or more other areas of your body.
• MX may be used if the stage of your cancer isn't clear.

If you need more information about the stage of your cancer or what it means, ask your doctor or surgeon.

Number staging system

Some cancers, including lymphomas and liver cancer, aren't described using the TNM system. If you have a tumour that isn't classified by TNM, your doctor or surgeon may describe it with a numbered stage - ranging from 1 to 4.

The higher the number, the more your cancer is likely to have spread in your body. For example, Stage 1 (or early stage) refers to a small tumour that hasn't spread to your lymph nodes and Stage 4 (or advanced stage) refers to tumours that have spread to other major organs in your body. Your doctor or surgeon may also use a letter with a stage number to define your cancer further - for example, stage 2a or 2b - to refer to the tissues that the cancer has spread into, but this will depend on the particular type of cancer you have.

Dukes staging system

If you have bowel cancer, your doctor or surgeon may describe it using the Dukes lettered (A-D) system. However, the TNM system is gradually replacing Dukes letters.

• Dukes A means your tumour is contained within the wall of your bowel.
• Dukes B means your tumour has grown into the muscle of your bowel wall, but has not spread to any nearby lymph nodes.
• Dukes C means one or more of your lymph nodes near your bowel are affected.
• Dukes D means your original tumour has spread to other parts of your body.

Grading

Grading is used to describe what your tumour looks like under a microscope to get an idea of how it may progress.

If your doctor or surgeon suspects you have cancer, he or she will take a sample of cells from your tumour (a biopsy) to send to a laboratory for testing. The cancerous cells will be looked at under a microscope to try and find out the speed at which your tumour may grow and how aggressive it is. There are three grades used to rate cancer.

• Low grade, or grade 1, refers to cancers that are slow growing. If your cancer is low grade, the cancerous cells may look much like other, healthy cells in your body. Low grade cells may be referred to as 'well differentiated'. They are less likely to spread.
• Moderate (intermediate) grade, or grade 2, refers to cancers that are growing slightly faster and are more likely to spread than low grade cancers. At this stage, the cancerous cells are known as 'moderately differentiated' and look different from healthy cells in your body.
• High grade, or grade 3 cancer cells look very different from healthy cells in your body. If you have a high grade cancer this means the cancerous cells are likely to grow faster and spread more easily than moderate grade cancer cells. They may also be called 'poorly differentiated' or sometimes 'undifferentiated', or 'anaplastic' cancerous cells.

If you are unsure about how your cancer may be graded or need more information, ask your doctor or surgeon.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.