Does mammography always find breast cancer?
Mammography is not perfect. 5-10% of mammograms show a false positive. This means that they show a cancer that is not really there. On the other hand, mammography also can miss 10-15% of breast cancers that are actually there. There can be a variety of reasons for this: 1) Some tumors can’t be seen very well by x-ray, 2) mammography is less effective for younger women because the breast tissue of younger women is more glandular and fibrous, which is hard for the x-ray to penetrate. As women get older, a higher percentage of their breast tissue is fat. Because x-rays see through fat quite easily, the older a woman is the more effective mammography will be in detecting breast cancer.
