Breast cancer stages

The stage of a cancer describes the size of the cancer and how far it has spread. 

Your breast cancer may be described as stage 1, stage 2, stage 3 or stage 4. 

An early form of breast cancer called DCIS is sometimes referred to as stage 0 breast cancer.

The stage takes into account:

• The size of the cancer
• Whether the lymph nodes are affected
• If the cancer has spread to other parts of the body

Your treatment team might not be sure of the stage of your cancer until after you have had surgery. 

Your treatment team will look at different information about your cancer to decide the best treatment for you, including:

• The cancer stage
• The size of the cancer
• The cancer grade
• The type of cancer
• If the cancer has hormone receptors or is HER2-positive

Stage 1 breast cancer

Stage 1 breast cancer is divided into 2 groups: stage 1A and stage 1B.

Stage 1A means the cancer is 2cm or smaller and has not spread outside the breast.

Stage 1B can mean one of the following:

• No cancer is seen in the breast, but a very tiny area of breast cancer (0.2mm–2mm) is found in the lymph nodes under the arm (known as micrometastasis)
• The cancer in the breast is 2cm or smaller and a very tiny area of breast cancer (0.2mm–2mm) is found in the lymph nodes under the arm (micrometastasis)

Stage 2 breast cancer

Stage 2 breast cancer is divided into 2 groups: stage 2A and stage 2B

Stage 2A can mean one of the following:

• No cancer is seen in the breast but cancer is found in 1 to 3 lymph nodes under the arm or near the breastbone
• The cancer in the breast is 2cm or smaller and cancer is found in 1 to 3 lymph nodes under the arm or near the breastbone.
• The cancer in the breast is larger than 2cm but smaller than 5cm and no cancer is found in the lymph nodes under the arm.

Stage 2B can mean one of the following:

• The cancer in the breast is larger than 2cm but smaller than 5cm. Cancer is found in 1 to 3 lymph nodes under the arm or near the breastbone
• The cancer in the breast is larger than 5cm and no cancer is found in the lymph nodes under the arm.

Stage 3 breast cancer (sometimes called locally advanced breast cancer)

Stage 3 breast cancer is divided into 3 groups: stage 3A, stage 3B and stage 3C

Stage 3A can mean one of the following:

• No cancer is seen in the breast, but cancer is found in 4 to 9 lymph nodes under the arm or near the breastbone
• The cancer in the breast measures up to 5cm and cancer is found in 4 to 9 lymph nodes under the arm or near the breastbone
• The cancer in the breast is larger than 5cm, and cancer is found in up to 3 lymph nodes under the arm or near the breastbone

Stage 3B means:

• The cancer in the breast can be any size, it has spread to the skin of the breast or the chest wall and cancer is found in up to 9 lymph nodes under the arm or near the breastbone

Stage 3C means:

• The cancer in the breast can be any size, it may have spread to the skin of the breast or the chest wall, cancer is found in 10 or more lymph nodes under the arm or near the breastbone, or to nodes above or below the collarbone

Stage 4 breast cancer

Stage 4 breast cancer is also known as secondary breast cancer.

Stage 4 breast cancer means:

• The tumour can be any size
• The lymph nodes may or may not contain cancer cells
• The cancer has spread (metastasised) to other parts of the body such as the bones, lungs, liver or brain

If your cancer is found in the lymph nodes under the arm but nowhere else in the body, you do not have stage 4 breast cancer.

Some doctors use the TNM staging system. This is a scoring system used to describe:

• The size of the cancer (T stands for tumour)
• The number of lymph nodes affected (N stands for nodes)
• Whether there’s any spread of the cancer to other parts of the body (M stands for metastases)

The individual scores are then grouped together to get an overall stage.