Estrogen receptors (ER) and progesterone receptors (PR) are usually found in the tissues where their respective target hormones play a regulatory role, such as the uterus, pituitary gland, hypothalamus, and breast. The respective receptors form a large protein complex upon hormone binding that activates transcription. As these receptors are tissue-based, determining their presence or absence requires representative tissue sampling.
Both ER and PR are used in breast cancer as indicators for hormonal therapy. Those positive for ER and PR will typically respond to hormonal treatment, while those with negative receptors will require other treatment modalities, such as chemotherapy.2
Patients with positive ER and PR typically have a better prognosis and a higher survival rate.
