The Food and Drug Administration announced Wednesday that it has begun investigating the possible connection between breast implants and an increased risk of a rare form of cancer.
Though the number of women who may develop the disease is small, there is apparently no way to identify those who are likely to develop it — making it a source of potential concern to all women with the implants.
Among women who do not have implants, the cancer — anaplastic large cell lymphoma, or ALCL — develops in the breast tissue of about 3 out of 100 million women nationwide.
But among women who do have implants, FDA investigators say they have identified as many as 60 women who have developed ALCL worldwide, out of an estimated global population of 5 million to 10 million women with implants.
The FDA did not provide an incidence number for women with implants who developed the disease in the United States alone.
The agency said the number of known cases was too few to draw a conclusion that implants were linked to the disease.
FDA officials emphasized the small risk and said that women with implants don't need to do anything more than be vigilant.
The FDA advised women not to change their routine medical care, but it said they should consult a physician if they notice swelling, pain or lumps around implants after postsurgical healing.
"Women who are not showing any symptoms or problems require only routine follow-up.... FDA is not recommending the routine removal of breast implants," said William Maisel, chief scientist and a deputy director of the FDA's medical device office.
ALCL is a treatable cancer of the immune system, and its occurrence in the breast does not equate to breast cancer, Maisel said.
"I think there's reason to be concerned about this, but there shouldn't be reason for panic," said Phil Haeck, president of the American Society of Plastic Surgeons. Signs of ALCL associated with implants "are pretty dramatic. There's a lot of swelling and pain. They won't miss it," Haeck said.
To better understand the development of ALCL, the plastic surgeons group has agreed to report all cases of ALCL to a national registry established by the FDA.
The FDA also will ask the two U.S. manufacturers of implants, Allergan of Irvine and Mentor Worldwide Santa Barbara, to update product labeling to include information about ALCL.
"We fully support FDA's efforts to gather additional data and study ALCL in patients with breast implants," Mentor said in a statement.
An Allergan spokeswoman said in a statement that when ALCL has occurred, "most of the patients have responded to a variety of treatments, including simple removal of the implant and surrounding scar capsule."
"A woman is more likely to be struck by lightning than get this condition," the statement said.
But the head of a leading women's health advocacy group said that the risk, while small for individuals, is still alarming.
"It raises a red flag about what other immune disease could be occurring that are not obvious," said Diana Zuckerman, president of the National Research Center for Women & Families.
Zuckerman noted that there have been reports that Allergan and Mentor have lagged in meeting benchmarks for 10-year safety studies of implant recipients required by the FDA.
Maisel said the FDA would give a status report on the studies this spring.
The FDA based its announcement on a review of scientific literature between 1997 and last May, which reported 34 cases of ALCL in women with breast implants, as well as other information from international regulatory agencies, scientific experts and implant manufacturers, which turned up additional cases.
About 355,000 women received implants in 2009, according to the plastic surgeons society, with about 290,000 receiving them for cosmetic purposes and 65,000 receiving them for reconstruction following breast cancer or other disease.
The concern about ALCL applies to women with both silicone and saline-filled implants and to those who had the implants for cosmetic reasons and for breast reconstruction.
ALCL cropped up in women with implants between one and 23 years after implantation surgery, with a median time of eight years between surgery and diagnosis.
Like many medical devices, breast implants came on the market before FDA oversight extended to them and so were not subject to extensive testing.
In 1992, the FDA imposed a moratorium on silicone implants for cosmetic purposes, lifting it in 2006 after years of fierce debate over their safety among women's groups, doctors, the medical device industry and consumer advocates.