TUESDAY, Nov. 4 (HealthDay News) -- Women with silicone breast implants may have a higher risk of developing a rare form of lymphoma, new research suggests.

But the absolute risk of developing this cancer is still tiny, amounting to about 0.1 to 0.3 per 100,000 women with implants each year, according to the Dutch authors of a study published in the Nov. 5 issue of the Journal of the American Medical Association.

"Doctors should be aware of this . . . but it's not something women should worry about," said Dr. Mitchell Smith, head of the lymphoma service at Fox Chase Cancer Center in Philadelphia. "People with implants have a one in many hundreds of thousands or one in a million chance of developing this cancer."

More importantly, Smith said, the finding might help scientists understand the biology of this particular malignancy.

Silicone breast implants have engendered decades of controversy. In 2006, the U.S. Food and Drug Administration lifted a 14-year ban on their commercial use, giving approval to two companies, Allergan Inc., of Irvine, Calif., and Mentor Corp, of Santa Barbara, Calif., to market the implants to all women aged 22 and older.

Neither company responded to requests from HealthDay for comment on the finding.

The implants had been removed from the market in 1992, following suspicions that they might cause cancer or certain autoimmune diseases. There were also concerns that the implants might interfere with the accuracy of breast cancer screening, or that ruptures would cause other health problems.

Researchers have identified previous cases of non-Hodgkin lymphoma in women with breast implants, and most of these were anaplastic large T-cell lymphoma (ALCL).

Normally, ALCL is exceedingly rare, representing 3 percent or less of all non-Hodgkin lymphoma in adults, and there are no known risk factors.

The authors of this study, at the Netherlands Cancer Institute in Amsterdam, searched a national database in the Netherlands for all cases of lymphoma in the breast diagnosed between 1990 and 2006.

They found 11 patients with ALCL, five of whom had had breast implants one to 23 years before their diagnosis. This was out of a total population of 8 million Dutch women over 17 years.

Compared with women who had other types of lymphoma in the breast, women with silicone breast implants had an 18-fold greater risk for developing ALCL.

The authors hypothesized that an immune system response related to placement of the implants or toxic damage from the implants might explain the association.

"There has been a lot of information about silicone and autoimmune disorders," Smith said. "Lymphomas do occur in other immune-deficiency states where you have chronic stimulation of parts of the immune system. It makes some sort of sense that this could happen."

More information

Visit The Leukemia & Lymphoma Society for more on different types of lymphoma.