What are receptors?

Breast cancer cells may have receptors (proteins) that hormones or a protein called HER2 can attach to and encourage the cells to grow. A pathologist tests the cancer cells that were taken during the biopsy or surgery for these receptors.

The results help you and your doctor decide on the most effective treatment for you.

Hormone receptors

Hormones help control how cells grow and what they do in the body. Hormones, particularly oestrogen, can encourage breast cancer cells to grow.

Breast cancer that has receptors for the hormone oestrogen is called oestrogen receptor-positive (ER-positive) breast cancer. The term ER is used because the American spelling of oestrogen is estrogen. About 70% of breast cancers are ER-positive. Hormonal therapies work well for ER-positive breast cancer.

Breast cancer that does not have hormone receptors is called oestrogen receptor-negative (ER-negative) breast cancer.

Breast cancer cells may also have receptors for the hormone progesterone (PR-positive).

Receptors for HER2

Some breast cancers have too much of a protein (receptor) called HER2 (human epidermal growth factor receptor 2) on the surface of their cells. This is called HER2-positive breast cancer. The extra HER2 protein encourages the cancer cells to divide and grow.

Between 15 and 20 out of every 100 women with breast cancer (15 to 20%) have HER2-positive cancers.

Specific targeted therapy drugs are used to treat HER2-positive breast cancer. They lock on to the HER2 protein and stop the cells dividing and growing.

Triple negative breast cancer

Cancer that does not have receptors for either HER2 or the hormones oestrogen and progesterone is called triple negative breast cancer. It affects up to 1 in 5 women (15 to 20%) with breast cancer and is more common in younger women.

About our information

  • References

    Below is a sample of the sources used in our breast cancer information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    European Society for Medical Oncology. Primary breast cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. Annals of oncology 26 (supplement 5): v8–v30. 2015.

    Morrow M, et al. Chapter 79: malignant tumors of the breast. DeVita, Hellman and Rosenberg’s cancer: principals and practice of oncology (10th edition). Lippincott Williams and Wilkins. 2014.

    National Institute for Health and Care Excellence (NICE). Early and locally advanced breast cancer: diagnosis and management. July 2018.

    Scottish Intercollegiate Guidelines Network. SIGN 134. Treatment of primary breast cancer: a national clinical guideline. September 2013.


  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Rebecca Roylance, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.