What are the risk factors for breast cancer?

A risk factor is anything that affects your chance of getting a disease, such as cancer.
Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for cancers of the lung, mouth, larynx (voice box), bladder, kidney, and several other organs.

But risk factors don't tell us everything. Having a risk factor, or even several, does not
mean that you will get the disease. Most women who have one or more breast cancer risk
factors never develop the disease, while many women with breast cancer have no
apparent risk factors (other than being a woman and growing older). Even when a woman
with risk factors develops breast cancer, it is hard to know just how much these factors
may have contributed to her cancer.

There are different kinds of risk factors. Some factors, like a person's age or race, can't be
changed. Others are linked to cancer-causing factors in the environment. Still others are
related personal behaviors, such as smoking, drinking, and diet. Some factors influence
risk more than others, and your risk for breast cancer can change over time, due to factors
such as aging or lifestyle.

Risk factors you cannot change : Gender, Aging , Genetic risk factors