A new study estimates that 15 to 25 percent of the breast cancers found by mammograms wouldn't have caused any problems and are unnecessarily treated.
The study appears in the Annals of Internal Medicine.
For years, women have been urged to get screened for breast cancer, because the earlier it is found the better. But this study suggests that is not always the case.
Once detected, early tumors are surgically removed and sometimes treated with radiation or chemotherapy because there is no certain way to figure out which ones may be dangerous.
It's the latest study to explore over-diagnosis from routine mammograms finding tumors that grow so slowly or not at all and that would not have caused symptoms or death.