Does taking estrogen cause 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.

There is indirect : Evidence that associates estrogen cycling with development of breast cancer: early onset of menses, late menopause, use of birth control pills, few pregnancies (therefore "excess" cycling estrogen) and use of post menopausal Estrogens for hot flashes all are more common with those developing breast cancer than those that have fewer to none of these factors. Something else caused; e promotes, grows.