Aromatase inhibitors are a type of medication used to treat hormone receptor-positive breast cancer. They work by blocking an enzyme called aromatase, which is responsible for producing estrogen in postmenopausal women and men with prostate cancer. Estrogen can stimulate the growth of certain types of breast cancer cells, so by reducing estrogen levels or blocking its effects, aromatase inhibitors can help slow down or stop the growth of these cancer cells. This type of medication is often used after other treatments such as surgery, radiation therapy, and/or hormone therapy to prevent the recurrence of breast cancer.