estrogen receptor (ER)

The estrogen receptor (ER) is a protein found inside some cells, especially in breast tissue, that binds to the hormone estrogen. When estrogen attaches to the ER, it activates the receptor, which then influences the cell’s behavior by turning on or off specific genes. This process helps regulate various functions like growth, development, and reproductive health. In some breast cancers, cells have many ERs, making the cancer responsive to hormonal therapies that target these receptors. Understanding ER status in tumors helps guide treatment options to improve patient outcomes.