Mutations of the p53 gene may also increase a woman's risk of breast cancer. Women who have had breast cancer in one breast are three to four times as likely to develop breast cancer in the opposite breast than women who have never had breast cancer. These conditions are characterized by a sharp increase in the number of breast cells. Women with fibrocystic change are not at increased risk for breast cancer. Most health care providers agree that daily alcohol consumption increases breast cancer risk.
Smoking increases a woman's chance of developing several types of cancer, including breast cancer.
However, the link between diet and breast cancer risk is complicated and is affected by the type of fat in a woman's diet. Monounsaturated fats, such as canola oil or olive oil have been linked to lower breast cancer risk while a diet high in polyunsaturated fats such as corn oils, tub margarine, and saturated fats in meats are associated with a higher risk of breast cancer. The link between weight and breast cancer risk is controversial. Also, overweight women who take hormone replacement therapy are at greater risk of developing breast cancer. Women whose breasts have been exposed to radiation therapy during childhood are at higher risk of developing breast cancer, especially if radiation was used to treat Hodgkin's disease.