A new study suggests that, in the US, more than half of women newly diagnosed with breast cancer after a mammogram were misdiagnosed. Published in The New England Journal of Medicine, the study concludes that, contrary to the belief that widespread screening has played a primary role in the lowering of mortality rates for those diagnosed, such advances are due primarily to improvements in treatment. Dr. H. Gilbert Welch, a professor at Dartmouth University who led the study, said that the medical community and the media “quite simply have overstated the value” of widespread screening. Still, the researchers note that mammography can be lifesaving. In 20% of cases in which a small tumor was detected by a mammogram, those small tumors were dangerous, and would’ve grown had they gone undetected.