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The types of metastatic breast cancer

It is important that you find an oncologist and care team whom you trust and feel comfortable with, to ensure that you are getting the best care possible every step of the way.

What is MBC?

Metastatic breast cancer (MBC) is cancer that has spread from the breast to different parts of your body. A tumour (also known as a carcinoma or an adenocarcinoma) in these areas is called a metastasis.

What are the different types of MBC?

Once you have received a diagnosis of MBC, your doctor will need to find out which type of cancer it is. This will help your doctor know which treatments may be best for you.

Breast cancer can have the genetic markers of HER2 and hormone receptors (HR) on your breast cancer cells. These markers can help guide effective cancer treatment. Chemotherapy (or chemo), anti-hormonal therapy, targeted therapy, radiotherapy and surgery are all treatment options.

  • Chemo-
  • Anti-
  • Targeted
  • Radiation
  • Surgery

There are four main types of MBC

Hormone receptor-positive, HER2-negative

This is the most common form of breast cancer found in approximately two-thirds of people. 

Hormone receptor-negative, HER2-positive

When breast cancer cells make too much HER2 protein, they grow faster than normal cells – and faster than other cancer cells. This is called HER2-positive breast cancer. Between 15–20% of breast cancers are HER2-positive. 

Hormone receptor-positive, HER2-positive

This is cancer that has both HER2 and hormone receptors. It has “tested positive” for both types. 

Hormone receptor-negative, HER2-negative, also called triple-negative

This cancer does not have HER2 or the hormone receptors oestrogen and progesterone. Between 10–20% of breast cancers are triple-negative

If your breast cancer recurs, your cancer cells should be retested for HER2 and hormone receptor status, since these can often change from the original cancer.

Why is my cancer referred to as ‘stage iv’ breast cancer?

There are four diferent breast cancer stages from 0 to IV based on how large the tumour is and whether it has spread to the surrounding lymph nodes and other parts of the body. MBC is stage IV (or stage 4 breast cancer). This means that the cancer has spread (metastasised) to other organs in the body.

Some doctors may also use another staging system known as the TNM classification (T for tumour, N for nodes, M for metastases) to assess the stage of your breast cancer. However, the TNM staging system is less common than the numerical staging system (stages 0–IV).

How is MBC different from early breast cancer?

Early breast cancer includes stages 0, stage 1 or stage 2 breast cancer. It refers to cancer that is still in the breast or which has only spread to lymph nodes near the breast. Treatment for early breast cancer usually happens for a limited period of time.

Metastatic breast cancer, otherwise known as stage IV (or stage 4 breast cancer), is when the cancer has spread (metastasised) from the breast to other organs in the body. This is the most advanced stage of breast cancer.

Advanced breast cancer usually refers to metastatic breast cancer, also called Stage IV breast cancer. Breast cancer that has spread locally in the area of the breast, but not to distant organs and tissues, is often referred to as "locally advanced breast cancer," or Stage III breast cancer.