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Instead, they had “variants of uncertain significance,” or VUS, genes that, in nine out of 10 cases, won’t result in cancer, says lead study author Allison Kurian, M.D., an associate professor of medicine and of health research and policy at Stanford.

And although clinical guidelines outline that women with VUS should be counseled similarly to a patient whose genetic test is normal, that’s not what the data found is happening. Many physicians surveyed said they would aggressively treat VUS with double mastectomy. More experienced surgeons who regularly see breast cancer patients were less likely to make this misstep—but still, one out of four more physicians in that group said they would treat uncertain results the same as a BRCA mutation.

“This was one of the most striking and unexpected findings. We didn’t expect surgery to be done on women who don’t have a risk-causing gene mutation,” says Kurian.

Related: This Reality Star’s Photos Show What A Mastectomy Really Looks Like?

Another worrying finding: Results of the genetic tests aren’t discussed with the right person and often aren’t discussed at the optimal time.

Only around half of women in the study ever discussed their results with a genetic counselor—something clinical guidelines say should happen every time. And roughly a third of the women only had genetic counseling after the breast-removing surgery had already been performed. Part of the problem is that there simply aren’t enough genetic counselors available, and many women, and their doctors, want to do surgery as quickly as possible. But Kurian points out that delaying surgery for a few weeks to wait for test results to come back shouldn’t be dangerous to most patients. (Subscribe to Women’s Health newsletter, So This Happened, to get the latest trending stories sent straight to your inbox.)

She notes that patients, too, need better education. “With the recent attention on double mastectomies, many seem to be patient driven,” says Kurian. Meaning, the women ask for them.

Here’s how to do a self breast exam:

Part of that demand undoubtedly stems from what doctors dub “the Angelina Jolie effect.” In 2013, the actress had a preventative double mastectomy after learning that she carried a mutation in the BRCA 1 gene that increased her breast cancer risk by 87 percent. Since then, younger women with breast cancer are increasingly opting to undergo double mastectomies, even if, like the women in Kurian’s study, they were diagnosed with early-stage cancer in only one breast, according to a study published in the journal JAMA Surgery.

Boosting our knowledge about genetic testing is even more important now, since tests have become cheaper (going from around $3,000 in 2013 to as low as $250 through Color Genomics). Many can be done at home by spitting into a tube and sending it off for analysis.

Related: What Angelina Jolie DIDN’T Teach Us About Breast Cancer

Kurian cautions against this route. “You should never undergo genetic testing without the guidance of an expert.”

If you suspect a breast cancer risk, she recommends first going to your family doctor and sharing your concerns. She can look at your family and personal health history and help you determine whether genetic testing is appropriate. If it is, she should refer you to a genetic counselor. If she doesn’t, ask her to make a referral, or find one on your own through the National Society of Genetic Counselors’ website, That expert can guide you through the process—and any potentially dangerous test results it reveals.