Hormones, proteins and breast cancer

Breast cancer can be described by the type of receptors or proteins on the surface of the breast cancer cells. Substances like hormones or proteins can attach to these receptors and help the breast cancer to grow. 

• Hormone-receptors: In breast cancer, some receptors mean that hormones will encourage the cancer cells to grow. For example, the hormones oestrogen or progesterone.
• HER2 protein: Your breast cancer cells may have too many HER2 proteins on their surface. HER2 can encourage breast cancer to grow.

Knowing about the receptors or proteins on the surface of your breast cancer cells can help the doctor decide which drug therapies will be most effective for you. For example, hormone therapy can block the action of the hormones that are helping the cancer to grow and targeted therapies can target HER2 proteins.

• ER positive breast cancer: The cancer cells have receptors for the hormone oestrogen or progesterone, which encourage the cancer cells to grow.  Read more about hormone-receptor positive breast cancer and how it’s treated.
• HER2 positive breast cancer: This means the breast cancer cells have large numbers of the HER2 protein receptors on their surface. HER2 can help the cancer cells to divide and grow.  Read more about HER2 positive breast cancer and how it’s treated.
• Triple negative breast cancer: This means the breast cancer cells don’t have receptors on the surface of the cancer cells for the hormones, oestrogen, progesterone or HER2. Read more about triple negative breast cancer and how it’s treated.