Next Page Chapter 5. Risk Factors for Breast Cancer 5.3 Family History Women with a first-degree relative who has had breast cancer have an increased risk of developing the disease. The reason for this increased risk reflects the fact that genes play a significant role in the development of certain cancers, including those of the breast. This coding is responsible for the function and growth pattern of the cell.
Cancer likely develops only after a series of different mutations has occurred.
Women with family histories most often inherit some, but not all, of the mutations necessary for the development of breast cancer. This increases their risk, but does not guarantee that a cancer will develop. The number of mutations inherited varies among patients. A woman with a mother and a sister diagnosed with breast cancer at the age of 40 inherits a much stronger genetic predisposition than a woman with a mother who developed the disease at age 70. There is a rare inherited condition in which nearly all female members develop breast cancer.