Dear Lulu, Having a family history of breast cancer (mother or sister) puts one at a moderately higher risk of breast cancer than the average woman. This risk increases if the relative had breast cancer prior to menopause or if the cancer was in both breasts. There is also noted higher risk to those carriers of a familial breast cancer gene, BRCA1. Women who've had a previous cancer in one breast, especially if it occured before menopause are at significantly higher risk. Other risk factors include early onset of menstruation and late onset of menopause, women who have never carried a term pregnancy or who were first pregnant after 30, obesity with excess caloric and fat intake.
The determination of a person’s individual risk is complex. Attempts have been made to quantify risk using various model’s for example the Gail model which assigns certain number values to risk factors and calculates a person’s risk based on age and a calculated risk number is given. This is only a tool, which can only tell a person their statistical risk based on its criteria. It cannot tell if you actually will get breast cancer.
Prophylactic mastectomy is done in certain situations for high risk women. The decision to pursue this option would involve determination of individual risk, and discussions of risk vs. benefit in the individual's own situation.