We know there are certain subsets of women that are at higher risk for developing breast cancer throughout their lifetimes and earlier. When you start having your period at 9 as opposed to 14 you had many years of unopposed estrogen on your breasts. Not having children, or having children later in life over the age of 30. African American women or women of Eastern European Jewish descent are at increased risks for developing breast cancer. The more dense your breast tissue is the harder the mammogram is to read. You could miss small cancers that are buried within this tissue and effectively have a false negative examination. Women that carry certain gene mutations that predispose them to developing breast or other cancers during their lifetime. So understanding your own personal risk for developing breast cancer is integral in being able to collaborate with your physician and deciding upon what is the best screening regimen for you.