After being female, age is the most significant risk factor for developing breast cancer. The older you are, the higher your risk. Most breast cancers (80%) occur in women over the age of 50. Most men who get breast cancer are over 60.
Most breast cancers are found in women who are 50 years old or older.
Some women will get breast cancer even without any other risk factors that they know of. Having a risk factor does not mean you will get the disease, and not all risk factors have the same effect. Most women have some risk factors, but most women do not get breast cancer.