Hormone and HER2 receptors
Some breast cancer cells have receptors, which allow particular types of hormones or proteins to attach to the cancer cell. The pathologist examines the tissue that’s been removed during surgery and carries out tests for hormone or protein receptors on it.
Some breast cancers have receptors for the hormones oestrogen and progesterone. If there are a significant number of oestrogen receptors, it’s known as oestrogen-receptor positive or ER positive breast cancer. If not, it’s known as oestrogen-receptor negative or ER negative breast cancer. The term ER is used because the American spelling of oestrogen is estrogen.
ER positive breast cancers respond well to hormonal treatments. About 70% of breast cancers are ER positive.
Some breast cancers have receptors for the protein HER2 (human epidermal growth factor 2). Cancers that have high levels of these receptors are called HER2 positive breast cancers. They respond well to treatment with trastuzumab, which is commonly called Herceptin®.
Some breast cancers don’t have receptors for oestrogen, progesterone or HER2. This type of breast cancer is known as triple negative breast cancer. After surgery, chemotherapy is the main treatment for triple negative breast cancer.