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What are estrogen and progesterone receptors in breast cancer?

Receptors are proteins on the outside surfaces of cells that can attach to certain substances, such as hormones, that circulate in the blood. Normal breast cells and some breast cancer cells have receptors that attach to estrogen and progesterone. These 2 hormones often fuel the growth of breast cancer cells.
An important step in evaluating a breast cancer is to test a portion of the cancer removed during the biopsy (or surgery) to see if they have estrogen and progesterone receptors. Cancer cells may contain neither, one, or both of these receptors. Breast cancers that contain estrogen receptors are often referred to as ER-positive cancers, while those containing progesterone receptors are called PR-positive cancers. Women with hormone receptor–positive cancers tend to have a better prognosis and are much more likely to respond to hormone therapy than women with cancers without these receptors.
All breast cancers, with the exception of lobular carcinoma in situ (LCIS), should be tested for these hormone receptors when they have the breast biopsy or surgery. About 2 of 3 breast cancers contain at least one of these receptors. This percentage is higher in older women than in younger ones.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.