Hormone and HER2 receptors

Some breast cancer cells have receptors, which allow particular types of hormones or proteins to attach to the cancer cell. A sample of the breast tissue will usually be tested to see if it has these receptors. Whether particular receptors are present or not will affect the type of treatment that you will need.

Hormone receptors

Many breast cancers have receptors for the hormone oestrogen. When oestrogen attaches to these receptors, it causes the cancer cells to grow. If a breast cancer has a significant number of oestrogen receptors it is known as being oestrogen-receptor positive (ER+). If it doesn’t it is known as oestrogen-receptor negative (ER-). Knowing whether the tumour has oestrogen receptors or not helps the doctors to decide on the best treatment. A tumour that is ER+ is likely to respond to hormonal treatments|, whereas a tumour that is ER- will not respond. Oestrogen-receptors are known as ER because of the American spelling of oestrogen as estrogen.

Some breast cancers have progesterone receptors and are known as progesterone-receptor positive (PR-positive). Usually, cancers that are ER+ will also be PR+. Progesterone receptors are less important than oestrogen receptors in predicting the likely response to hormone treatment.

HER2 receptors

Some cancers have receptors for a protein known as HER2|. Tumours that have high levels of these receptors are known as HER2-positive and may respond to treatment with drugs such as trastuzumab (Herceptin®)|. Your doctor can tell you whether your cancer cells have these receptors.