The reason the results are so poor in younger women, is that younger women have denser breasts. Mammograms work by picking up densities (which many times indica

The reason the results are so poor in younger women, is that younger women have denser breasts. Mammograms work by picking up densities (which many times indicate a tumor. In younger women, the whole breast is dense and you really can't tell (especially with lower radiation doses). MRI can work, but it is much more expensive, and finding the exact location of the abnormality on MRI can be trickier.