A cancer associated with breast implants may be increasing, but is underreported, and patients and even doctors may not be aware of the risk, says a group of researchers at Penn State College of Medicine.

Breast implant-associated anaplastic large cell lymphoma — or BIA-ALCL — is a rare peripheral T-cell lymphoma type of cancer that may develop in patients with breast implants.

Researchers analyzed 115 research articles to learn more about the development, risk factors, diagnosis and treatment of BIA-ALCL.

"We're seeing that this cancer is likely very underreported, and as more information on this type of cancer comes to light, the number of cases is likely to increase in the coming years," said Dino Ravnic, assistant professor of surgery, Penn State College of Medicine.

"We're still exploring the exact causes, but according to current knowledge, this cancer only really started to appear after textured implants came on the market in the 1990s."

Although BIA-ALCL is estimated to affect 1 in 30,000 women with breast implants each year, the researchers said the cancer could be more common. All of the cases were associated with textured implants, which have a slightly rough surface that keeps the implant in position.

Textured implants became popular in the 1990s, and the first case of BIA-ALCL was documented in 1997. The researchers say that because they could find no incidents of BIA-ALCL prior to the introduction of textured implants, this suggests a causal relationship.

"All manufacturers of textured implants have had cases linked to this type of lymphoma, and we haven't seen cases linked to smooth implants," Ravnic said. "But in many of these cases the implant was removed without testing the surrounding fluid and tissue for lymphoma cells, so it's difficult to definitively correlate the two."

The researchers believe that inflammation surrounding the implant may spur the development of BIA-ALCL, and tissue that grows into the tiny holes in the textured implant may prolong that inflammation.

Previous research has shown that chronic inflammation can lead to lymphoma. In the cases analyzed, BIA-ALCL typically developed slowly, and patients who had both the implant and surrounding scar tissue removed had good prognoses.

Breast implant surgery is the most common implant surgery in the United States, and about 5 percent of American women have undergone the procedure.

The study was published in JAMA Surgery.