Is it true that female hormone therapy can increase the risk of breast cancer?

Yes: Certain hormones, especially longer use of estrogens, can increase a person's risk of breast cancer. Estrogen is listed as a known carcinogen on the fda web site & there is a class action lawsuit ongoing against premarin (conjugated estrogens). See site: http://m.Cancer.Org/cancer/cancercauses/othercarcinogens/generalinformationaboutcarcinogens/known-and-probable-human-carcinogens.

Very likely: There is considerabel evidence that estrogens(female hormone) plays an important role in genesis of breast cancer. This was best shown in women who took hormone replacement therapy(hrt) after menopause. So such therapy(hrt) is now discouraged whenever possible.