Are the cancer cells fueled by hormones?

Some breast cancers are sensitive to the hormones estrogen and progesterone. Pathologists look for hormone receptors on the outside of the breast cancer cells. Cancer cells use these receptors to catch hormones that are circulating in the body. The cells use the hormones for fuel to grow the cancer.

Hormone status of breast cancers includes:

• Estrogen receptor positive. A breast cancer that's estrogen receptor positive, also called ER positive, has receptors for the hormone estrogen. Treatment with hormone therapy can block the growth of the cancer cells. Another term for breast cancer hormone therapy is endocrine therapy.
• Progesterone receptor positive. A breast cancer that's progesterone receptor positive, also called PR positive, has receptors for the hormone progesterone. Treatment with endocrine therapy can block the growth of the cancer cells.
• Hormone receptor negative. A breast cancer that doesn't have hormone receptors is hormone receptor negative, also called HR negative. Endocrine therapy that blocks hormones in the body doesn't work for this type of breast cancer.

Most breast cancers have hormone receptors.