Cancers of the breast in women are common after the age of 35 years, and are more common if there is a family history of breast cancer (genetic factors). Cancers of the breast are more common in women who have not had any children before the age of 35 years. Being under age 20 years when first pregnant, having several pregnancies, and breast feeding all reduce the risk. Being overweight increases the risk. Cancer of the breast rarely occurs in men.
Breast cancer caused 0.8% of all deaths worldwide in 2002, an average of 77 deaths per million people per year and 7% of all deaths from cancer.