Risk of breast cancer no higher for most women with benign lesions: study

TORONTO (CP) - Most women with lumps or cysts in their breasts that turn out to be non-cancerous after biopsy do not have a greater risk of developing breast cancer, a U.S. study confirms.

That is especially true if they have no family history of breast cancer, concludes the study by researchers at the Mayo Clinic in Rochester, Minn. However, the study adds weight to previous research showing that some rarer types of benign breast disease are indeed linked to a higher risk of cancer and should be monitored regularly.

Benign breast disease is a catch-all category for a number of breast tissue conditions that have been biopsied but found to be non-cancerous.

"The biggest contribution in this (study) was to assure women with the most common form of benign breast disease, which is the nonproliferative cysts, that their risk is not increased unless they have a strong family history (of breast cancer)," said oncologist Dr. Lynn Hartmann, the study's lead author.

At the other end of the scale is breast tissue with what's known as atypical hyperplasia, which researchers found to be associated with a greater risk of developing cancer.

"In our study, if you have 'atypia,' your risk is four times increased," Hartmann said Wednesday. "Adding a family history to that does not further elevate your risk."

Less than four per cent of more than 9,000 women with benign breast disease in the study had atypical hyperplasia, in which the cells in the biopsied tissue are abnormal in size and shape and increased in number.

"Those are features on the way to what a cancer cell looks like," Hartmann said. "These are not normal cells."

About 30 per cent of the women had breast duct tissue that was classified as proliferative - the cells look normal but there are far too many of them.

Those women had a double-than-normal risk of developing breast cancer, she said. "It's not high-risk, but it's still something we want to be aware of. We want to be sure that a woman is getting good followup and doing her mammograms on time."

The study, published in Thursday's New England Journal of Medicine, involved reviewing the cases of 9,087 women aged 18 to 85, who had a biopsy of a benign breast lesion from 1967 through 1991. Women were followed for a median period of 15 years.

As of August 2004, almost eight per cent overall had developed breast cancer, with the highest proportion among those with atypical hyperplasia.

"Not all benign results are the same, and so understanding what the biopsy showed is a good thing," said Hartmann. "So what we're doing is providing some solid information about risk levels within the large group of benign breast disease, both for the women themselves and their physicians."