About breast cancer staging and grades

The TNM staging system

In the UK, the most common staging system for breast cancer is the TNM system. The TNM staging system stands for Tumour, Node, Metastasis.

• T describes the size of the tumour (cancer)

• N describes whether the cancer has spread to the ​lymph nodes​

• M describes whether the cancer has spread beyond the lymph nodes to a different part of the body  

Find out more about the TNM staging for breast cancer

The number staging system

The number staging system divides cancers into stages. There are 4 stages for breast cancer, numbered from 1 to 4:

• Stage 1

• Stage 2

• Stage 3

• Stage 4

You may also hear about stage 0 breast cancer. Stage 0 is used to describe ductal carcinoma in situ (DCIS). It is a pre invasive breast cancer. This means that the cancer cells are in the breast ducts and have not started to spread into the surrounding breast tissue.

Read about ductal carcinoma in situ

Early, locally advanced and secondary breast cancer

Your doctor may describe the cancer as early, locally advanced or secondary breast cancer.

Early breast cancer means the cancer hasn't spread beyond the breast or the lymph nodes in the armpit on the same side of the body. 

Locally advanced breast cancer means the cancer has spread into the surrounding area, such as the lymph nodes, the skin or the chest muscle. But it has not spread to other distant parts of the body.

Secondary breast cancer is also called metastatic breast cancer, advanced breast cancer, or stage 4 breast cancer. It means that the cancer has spread to other distant parts of the body, such as the liver or bones.

Grades of breast cancer

The grade describes how cancer cells and tissue look under a microscope and whether they are similar or very different to normal cells and tissue. It gives your doctor some idea of how the cancer might behave.

A specialist doctor called a ​pathologist​ checks the cancer cells for certain features. These include:

• the arrangement of the cells in relation to each other

• whether they form tubules

• how similar they look to normal breast cells

• how many of the cells are dividing (the mitotic count)

These features taken together tell the grade for the cancer. Low grade cancers tend to grow more slowly than high grade. High grade cancers are more likely to come back after they have first been treated. But the grade can only give a guide to how any individual cancer will behave and individual cancers may behave differently.

For breast cancer, there are 3 grades - from grade 1 to grade 3. 

Grade 1 

The cancer cells look similar to normal breast cells. These cancers tend to grow and spread slowly and have a good prognosis. This is also called low grade or well differentiated breast cancer.

Grade 2 

The cells look quite different to normal breast cells. This means the features and prognosis are somewhere between well and poorly differentiated. This is also called intermediate grade or moderately differentiated breast cancer. 

Grade 3

The cells look very different to normal breast cells. They tend to grow and spread more quickly and have a worse prognosis. These are also called high grade or poorly differentiated breast cancers.

Deciding on treatment for breast cancer

Your doctor looks at the stage and grade of the cancer and suggests the best treatment for you. They also consider other things when recommending treatment:

• the type of cell the cancer started in

• your age and general health

• how you feel about what the treatments involve and the side effects

Treatments you might have include surgery, chemotherapy and hormone therapy. 

Find out about treatment options for breast cancer