Age- Increasing age is important risk factor. About 60 percent of breast cancers occur in women over the age 60. Risk is greatest after age 75.
Previous breast cancer- At highest risk are women who have had in situ or invasive breast cancer.After the diseased breast is removed the risk of developing cancer in the remaining breast is about 0.5 to 1.0 percent each year.
Family history of breast cancer- Breast cancer in a first-degree relative (mother,sister,daughter)increases a woman's risk by two to three times, but breast cancer in more distance relatives (grandmother,aunt,cousin)increases the risk only slightly.Even a woman whose close relatives had breast cancer has no more than a 30 percent chance of developing breast cancer before agg 75.
Breast cancer gene- Recently, two separate genes for breast cancer have been identified in two separate small groups of women.If a women has one of these genes,her chances of developing breast cancer is very high.However if such a woman develops breast cancer her chances of dying of breast cancer are not necessarily greater than those of any other woman with breast cancer.Women likely to have one of these genes are those who have a strong family history of the disease; usually several women in each of three generations have breast cancer. For this reason routinely screening women for these genes doesn't appear necessary, except for women who have unusual family history. The incidence of ovarian cancer is also increased in families with one of the breast cancer genes.
Prolonged use of oral contraceptives or estrogen replacement therapy-
Most studies don't show any relationship between the use of oral contraceptives and the later development of breast cancer, except possibly for women who took them for many years
Obesity- Risk is somewhat higher in obese post menopausal women,but there is no proof that a particular diet- for example one high in fat-contributes to the development of breast cancer Some studies suggest that obese women who are still menstruating actually are less likely to develop breast cancer,
(Merck Manual)
