ESTROGEN RECEPTOR; ER

Estrogen receptor/progesterone receptor (ER/PR) tests are used to help guide breast cancer treatment. Receptors are proteins that attach to certain substances. ER/PR tests look for receptors that attach to the hormones estrogen and progesterone in a sample of breast cancer tissue. Estrogen and progesterone play key roles in a woman’s sexual development and reproductive functions. Men also have these hormones, but in much smaller amounts.