Each year, more than , American women and men are diagnosed with breast cancer. No one knows if or when breast cancer will develop, but understanding the risk factors for breast cancer may help you take preventive measures to reduce the likelihood of developing the disease. Breast cancer is caused when the DNA in breast cells mutate or change, disabling specific functions that control cell growth and division. In many cases, these mutated cells die or are attacked by the immune system. But some cells escape the immune system and grow unchecked, forming a tumor in the breast.
When we talk about factors that can increase or decrease the risk of developing breast cancer, either for the first time or as a recurrence, we often talk about two different types of risk: absolute risk and relative risk. It is based on the number of people who will develop breast cancer within a certain time period. Absolute risk also can be stated as a percentage. On average, an individual woman has a 1-in-8 chance of developing breast cancer over an year lifespan.
Not all women have the same risk for developing breast cancer over a lifetime. Certain factors increase a woman's risk, and some have a bigger impact on risk than others. However, having several risk factors doesn't mean you'll inevitably develop breast cancer. Likewise, having few risk factors doesn't mean that you'll never develop it. Many risk factors, such as age and gender, are not within our control.