What is estrogen receptor-positive breast cancer?

What is estrogen receptor-positive breast cancer?

Most breast cancer cells respond to hormones, specifically estrogen or progesterone. These hormones circulate in the blood. A cancer is called estrogen receptor-positive if it responds to estrogen. This means that estrogen triggers the cancer to grow. Progesterone receptor-positive breast cancer means that progesterone triggers the cancer to grow.

Knowing which hormone makes the cancer grow helps to determine the best way to treat or prevent breast cancer. One study showed that of the women who did develop breast cancer, 88% of the breast cancers were estrogen receptor-positive.