A risk factor is anything that makes it more likely you'll get a particular disease. Some risk factors, such as your age, sex and family history, can't be changed, whereas others, including weight, smoking and a poor diet, are under your control.
But having one or even several risk factors doesn't necessarily mean you'll develop cancer — most women with breast cancer have no known risk factors other than simply being women. In fact, being female is the single greatest risk factor for breast cancer. Although men can develop the disease, it's far more common in women.
Other factors that may make you more susceptible to breast cancer include: