A new breast cancer study, published in the Journal of the American Medical Association, is leaving researchers puzzled.
FOX News Radio's Lisa Brady explains why:
Breast cancer is still considered uncommon in women under age 40, hence that threshold for screening guidelines. So researchers comparing 1976 to 2009 were surprised to find a small, but significant increase in advanced cases of breast cancer in women ages 25-39.
(Dr. Pederson) "It can present at a much later stage and be much more deadly."
...Dr. Holly Pederson at Cleveland Clinic - not part of the study, led by researchers in Washington state who say there's probably more than one reason. Theories range from population and lifestyle changes to later pregnancies and hormone use, perhaps spreading a tumor more quickly. For now, no one knows for sure.
Lisa Brady, FOX News Radio.