Since the late 1970s, clinicians have distinguished breast cancers types according to the presence or absence of certain receptors that sit on the surface of these tumor cells. Depending on the receptors found—namely, the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2)—a doctor can get a better sense of the prognosis and which treatments might work. Read more Continue reading →