Estrogen increases the risk of endometrial cancer, but does it increase the risk of breast cancer as well?

Yes: Studies have shown an increase risk of breast cancer in patients treated with estrogen replacement. In fact, women at high risk for getting breast cancer are treated with tamoxifen or evista (raloxifene). Those drugs block the effect of estrogen on breast tissue.

Probably: The studies show mixed results, but most agree that long-term estrogen replacement may increase bc risk. My advice: short term ert (<3 years) is generally safe unless you have a bad family history or personal history of abnormal breast biopsies. I would take ert beyond 3-4 years only if you are truly miserable without it. After a few years most women can taper their ert.

Estrogen: That is a highly controversial topic with data going both ways. It is easier to say the combination of estrogen and Progesterone (together) in a postmenopausal women increases the risk of breast cancer.