Lumpectomies can save breasts, but surgeons often have difficulty finding the tumor edges—and this means women often need follow-up surgeries to get the rest of the breast cancer. Now, a new device helps tell surgeons right away if they got all of the tumor. Called MarginProbe, the device uses radio waves to detect tumor edges in tissue that has been removed. In a trial of 600 lumpectomies, women were more likely to avoid second surgeries with the device than without it (69% vs 58%). Ultimately, the device may be customized to work on other types of cancers.