When you introduce a medical device into your body, there’s always the chance that things could go awry: For example, a breast implant could shift, leak, or otherwise interfere with your health. Now, after years of studying the issue, the U.S. Food and Drug Administration says there appears to be a connection between breast implants and a rare form of cancer that has claimed at least nine lives.

The agency said this week that as of Feb. 1, 2017, it’s received 359 reports linking anaplastic large cell lymphoma (ALCL) with both silicone and saline breast implants. It’s impossible to nail down exactly how many cases exist, however, as the FDA says there’s a lack of worldwide sales data on implants and limited reporting of problems.

“All of the information to date suggests that women with breast implants have a very low but increased risk of developing ALCL compared to women who do not have breast implants,” the FDA says, noting that most cases can be treated by removing the implant and the capsule surrounding it, but some cases have required chemotherapy and radiation treatment.

While it doesn’t seem to matter what’s inside the implants, the outside texture could be a factor in causing ALCL: Of the 231 reports that included information on the implant surface, 203 were reported to be textured implants and 28 reported to be smooth implants, says the FDA.

It’s not known why the surface of an implant would be a risk factor, but one plastic surgeon and researcher explains to The New York Times that the body has a different reaction to textured implants than it does to smooth implants, because tissue grows in the microscopic grooves of textured implants.

“When we take these out, you can hear a peeling sound,” Dr. Alex K. Wong told the Times. “Whereas with a smooth implant, it’s like Jell-O. You can spin it around. It moves really easily.”

The FDA recommends that women getting implants should be aware of the potential problem with textured implants.

“Before getting breast implants, make sure to talk to your health care provider about the benefits and risks of textured-surface vs. smooth-surfaced implants,” the agency says.

If there are no problems, there’s no reason to remove an implant, the agency notes, adding that the lymphoma appears to be very rare.

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