What is the role of estrogen in breast cancer?

It can raise risk: Certain cancers are hormonally dependent. Specifically some breast cancer has become much more understood to be stimulated by unopposed estrogens. Not all breast cancer is caused by hormones. However the most common forms due tend to be hormonally dependent. There are other factors that lead to the development, but pros of taking hormones must be weighed against increased risk of breast cancer.

Stimulates the growt: About 80% of breast cancer are er positive which means that the cancer cells are stimulated to grow by estrogen in the body. Decreasing the estrogen levels with tamoxifen which is an estrogen blocker in premenopausal women and aromatase inhibitors which stop estrogen production in sites other than the ovaries in post menopausal women is an important treatment.