 One thing that is known to interfere with the early detection of breast cancer with mammograms is a womans breast density. Women under age 50 tend to have more density in their breasts than women who are older, but density may be present in women of all ages and is estimated to exist in 40 to 60 of all women who have mammograms. Women who have more fibrous connective and glandular tissue than fatty tissue in their breasts have more breast density. 