Mammograms: Facts on 'False Positives'

About 67 percent of women age 40 and older get a screening mammogram every one or two years. Of those who get screened, 16 percent will get called back for further testing if it’s their first mammogram, and 10 percent will be called after subsequent mammograms. Fortunately, very few of those who are called back will end up having cancer.

Callbacks may cause anxiety in a lot of women who don’t understand what they mean and who may not be aware of the complexity of mammography. A study recently released by the American Association for Cancer Research reported that women who have a history of false positive screening mammograms, or biopsies that were negative (no cancer was found) are at an increased risk of getting breast cancer within 10 years. Some may find this shocking but, for many radiologists who perform mammograms, it’s confirmation of what they already believed. Dr. Avice O’Connell, director of Women’s Imaging at UR Medicine, shares what women should know when it comes to false positives.

What is a false positive?

The phrase sounds scary, but really, it is a good thing. It means you do not have cancer but in your screening mammogram, your doctor recognized something that merited further imaging or even a biopsy.

If I am called back into the office for further testing, should I be worried?

It's not something to get extremely worried about. Of all women who receive regular mammograms, about 10 percent will get called back for further testing and of those, only about 0.5 percent will be found to have cancer. Your chances of being diagnosed with cancer after a callback are small, but your doctor wants to be sure there is no cancer present.

Another reason you could be called back is due to breast density. If your doctor discovers you have dense breasts, he or she is required to inform you through a written letter if you live in New York state as well as 24 other states. That’s because women with dense breasts have a slightly elevated breast cancer risk and it’s harder to detect breast cancer in dense breasts. Therefore, if you’re found to have dense breasts, you may want to consider additional testing.

Why are women with a history of false positives more likely to get breast cancer within 10 years?

First, it’s important to recognize the results of the recent AACR study about increased risk of breast cancer among women who’ve had false positives is not surprising for radiologists. When your radiologist assesses your risk for breast cancer, he or she already includes whether you’ve had negative biopsies or false positives in the calculation. Now this study reinforces that claim with data.

If you get a call back, it could be because your doctor notices a change or abnormality that is not currently cancerous. However, it might mean the radiologist observed suspicious findings on the mammogram that may be a marker of future cancer risk. Additionally, many women receive callbacks because of breast density and women with denser breasts are more likely to get breast cancer.

What’s the real takeaway of this study for women?

It’s very important for those over 40 years old to have annual mammograms. Getting it done yearly helps your radiologist see changes over time and allows her to further explore changes. This can potentially lead to catching breast cancer in earlier stages.

Mammography is not perfect, but it’s the gold standard and is mostly responsible for the 30 percent drop of mortality in breast cancer in the last 20 years.

Avice O’Connell, M.D., is professor of Imaging Sciences and director of UR Medicine Breast Imaging, which provides mammograms and other breast imaging, such as MRI and ultrasound. You can schedule a mammogram at UR Medicine’s many locations by calling (585) 487-3300.