WASHINGTON -(Dow Jones)- The Food and Drug Administration is investigating a possible link between breast implants and a rare type of cancer, reopening a debate about the safety of implants.

Specifically the FDA is looking at reports of a type of lymphoma called anaplastic large cell lymphoma that's mostly been found adjacent to the breast implant. ALCL is a type of non-Hodgkin's lymphoma and is not breast cancer.

The FDA said it's aware of just 60 cases since 1997 of ALCL in women with both silicone and saline implants, a small number compared to the estimated 5 million to 10 million women worldwide who have implants.

ALCL appears in different parts of the body including the lymph nodes and skin, according to the National Cancer Institute. Each year ALCL is diagnosed in about 1 out of 500,000 women in the U.S. ALCL in the breast is even more rare with 3 out of 100 million women per year diagnosed in the U.S., FDA said.

"Data reviewed by the FDA suggest that patients with breast implants may have a very small but significant risk of ALCL in the scar capsule adjacent to the implant," the agency said in a statement. But because the risk of ALCL appears to be "very small," FDA said it believes there's a "reasonable assurance" that implants are safe and effective.

In the U.S., breast implants are sold by Allergan Inc. (AGN) and Mentor Worldwide LLC, a unit of Johnson & Johnson (JNJ).

An Allergan spokeswoman said, "Patient safety is Allergan's absolute first priority and we continue all efforts to collect and analyze further information about the very rare occurrence of ALCL in patients with breast implants."

A spokesman for Mentor said, the company "fully supports FDA's efforts to gather additional information and study ALCL in patients with breast implants.

William Maisel, FDA's chief scientist and a deputy director in the agency's device division, urged doctors to notify the FDA about any confirmed cases of ALCL in patients with implants. He said the agency is working to establish an ALCL patient registry to better establish if there's a link between implants and that type of cancer.

The FDA said it started a review of ALCL and implants after receiving case reports. The FDA said it identified 34 cases of ALCL from 1997 through May 2010 from the medical literature. The agency then contacted other regulatory agencies, scientists and the companies to find a total of 60 cases. However, the FDA stressed that some case reports might be duplicates.

The agency said it would work with Allergan and Mentor to update labeling materials for patients and health care providers to discuss the possible risk of ALCL.

Of the 34 reports seen in the medical literature, 24 were in women with silicone implants and seven were reported in women with saline implants. In three cases the type of implant wasn't identified.

One theory the FDA is looking at is whether the silicone itself might play a role in ALCL. Maisel said both types of implants are "surrounded" by silicone.

The FDA sharply curbed the use of silicone-gel implants in 1992 after concerns were raised about whether leaking silicone gel caused serious health problems, requiring women who wanted to increase their breast size for cosmetic purposes alone to use saline implants. In 2006 silicone implants were allowed back on the market for cosmetic use to women age 22 and older.

Dow Corning Inc., a former silicone-gel implant maker, filed for bankruptcy protection in 1995 after thousands of lawsuits over its implants. The company later emerged from bankruptcy protection started paying out $2.35 billion in claims to thousands of women who sued the company over allegations they were injured by silicone implants. Dow Corning is equally owned by Dow Chemical Co. (DOW) and Corning Inc. (GLW).

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