WEDNESDAY, Jan. 26 (HealthDay News) -- The U.S. Food and Drug Administration said on Wednesday that breast implants may be linked to a heightened risk for a rare cancer, as evidenced in a small but growing number of cases that have been reported in recent years.

The agency now says that both silicon and saline implants may be linked to anaplastic large cell lymphoma (ALCL), which could develop within the scar tissue left by the implant procedure.

But the absolute risk to any one woman is likely to be very low, experts stressed.

"Lymphoma is a cancer involving cells of the immune system and ALCL is a very rare type of lymphoma," Dr. William Maisel, chief scientist and deputy director for science at the FDA's Center for Devices and Radiological Health, said during an early afternoon press conference Wednesday.

"The FDA believes that women with breast implants may have a small, but increased, risk of developing ALCL," he said. Only about one of every 500,000 American women each year are diagnosed with ALCL, Maisel said, and "ALCL in the breast is even more rare, occurring in three of every 100 million in the United States."

He added that "ALCL in the breast is not the same as breast cancer."

Of the 5 million to 10 million women around the world who have implants, the FDA says it now knows of roughly 60 cases of ALCL. That number has been tough to verify, the agency said, since some cases may have been duplicated in separate reports.

The agency is asking doctors to report any cases of ALCL, and for makers of implants to update their labeling and other information to disclose the potential hike in risk to both doctors and patients.

The agency's decision is also based of studies published from 1997 to 2010 that identified 34 cases of ALCL among women with either silicon or saline implants around the world, Maisel said.

Among these cases, 24 were related to silicon implants, seven to saline implants and the type of implant in the remaining three cases are not known, according to the FDA. In addition, 19 of the implants were inserted for cosmetic reasons and 11 were used in reconstructive procedures. The reasons for the other four procedures are not known, the agency said.

The majority of cases the agency is aware of came to light when women went to a doctor complaining of symptoms such as pain, lumps, swelling or anomalies in their breasts. These symptoms were the result of "fluid, hardening of breast area around the implant, or masses surrounding the breast implant," the agency said. ALCL was found by testing the fluid and area around the implant.

Symptoms of ALCL can develop from one to 23 years after a women gets her implants, according to the FDA.

"Women with breast implants who are not showing any symptoms or problems require only routine follow-up," Maisel said. "Physicians should consider the possibility of ALCL if the patient has late-onset and persistent fluid around the implant," he added.

"Women should monitor their implants and report any noticeable changes to their doctors, particularly those that occur after the breast implants are fully healed," Maisel said.

ALCL is usually treated with chemotherapy and radiation, and sometimes surgery, Maisel noted.

"I suspect this has caught the vast majority of plastic surgeons off-guard, as we have not heard anything remotely related to a potential warning before today," said Dr. Jeffrey C. Salomon, an assistant clinical professor of plastic surgery at Yale University School of Medicine.

This rare lymphoma develops in the naturally occurring capsule of tissue that normally forms around the implant, he said. "It is somewhat distressing to surgeons and patients alike but, the overall risk is exceedingly low," Salomon added.

Maisel added that American Society of Plastic Surgeons (ASPS) is working with the FDA to set up a registry of cases so the agency can get a better idea of the relationship between implants and ALCL.

However, the president of the society was wary of the public overreacting to the risk.

"ASPS shares the FDA's commitment to patient safety, but we also want to make certain this information does not raise false alarms with our patients," Dr. Phillip Haeck said in a statement. "We've been down this path before. For nearly 20 years, American women were denied access to their choice of breast implants because of false claims and unfounded science. We are determined this shouldn't happen again."

Haeck is referring to the belief that silicon implants were associated with breast hardening, breast pain, breast implant rupture, and the need for additional surgery and a possible risk of cancer, which caused the FDA to ban them for 14 years.

After further review, the FDA allowed silicon implants to return to the market in 2006.

Commenting on the FDA's announcement, Dr. Jasmine Zain, director of the Rita J. and Stanley H. Kaplan Stem Cell/Bone Marrow Transplant Center and an assistant professor in the department of medicine at the NYU Langone Medical Center in New York City, said that she was "aware of the link between breast implants and ALCL."

"About five years ago, my colleagues and I discovered that there was a link between lymphoma and breast implants in several patients we treated. Over the years, other doctors have noted the link between rare lymphoma and breast implants. The occurrence is very rare, but women have to be very careful," Zain said. "Women should be aware of the risk when deciding whether or not to get breast implants. Women thinking about getting breast implants and women with breast implants should talk to their doctors and be informed of the risk."

More information

For more information on breast implants, visit the U.S. Food and Drug Administration.