Women with atypical hyperplasia of the breast have a higher risk of developing breast cancer than previously thought, a study has found. Its results appeared in a special report on breast cancer in the New England Journal of Medicine (2015; doi:10.1056/NEJMsr1407164).

Atypical hyperplasia of the breast is a precancerous condition found in about one-tenth of the more than 1 million breast biopsies with benign findings performed annually in the United States. Viewed under a microscope, atypia contains breast cells that are beginning to grow out of control (hyperplasia) and cluster into abnormal patterns (atypical). The lesions are considered benign, but by their risk and appearance and genetic changes, they exhibit some of the early features of cancer.

Data from hundreds of women with these benign lesions indicate that their absolute risk of developing breast cancer grows by more than 1% a year. The study found that after 5 years, 7% of these women had developed the disease; after 10 years, the number of women increased to 13%; and after 25 years, 30% had breast cancer.

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The finding places the more than 100,000 women each year with an atypical hyperplasia diagnosis, which is also known as atypia, into a high-risk category, where they are more likely to benefit from intense screening and use of medications to reduce risk.

“By providing better risk prediction for this group, we can tailor a woman’s clinical care to her individual level of risk,” said lead author Lynn Hartmann, MD, an oncologist at Mayo Clinic in Rochester, Minnesota. “We need to do more for this population of women who are at higher risk, such as providing the option of MRI screenings in addition to mammograms and encouraging consideration of antiestrogen therapies that could reduce their risk of developing cancer.”

Previous research has shown that women with atypia have a fourfold to fivefold increased relative risk, meaning that they are four to five times more likely to develop breast cancer than women who don’t have these lesions. But few studies have had the patient numbers and follow-up time to report patients’ absolute risk, meaning the chance that she will develop breast cancer over a certain period of time.

To clearly define this risk, the Mayo Clinic team followed 698 women with atypia who underwent biopsy at Mayo Clinic between 1967 and 2001. They reviewed pathology and medical records, and used patient follow-up questionnaires to determine which women developed breast cancer and when. The researchers found that after an average follow-up of 12.5 years, 143 women had developed the disease.

Importantly, the Mayo findings were validated by researchers at Vanderbilt University using biopsies from a separate cohort of women with atypia. Both data sets revealed that at 25 years following biopsy, 25% to 30% of these women had developed breast cancer.

The research team recommends that women with atypical hyperplasia be recognized as having significantly increased lifetime risk of breast cancer and thus be candidates for screening MRI. Moreover, antiestrogen medications such as tamoxifen have already been tested in clinical trials in women with atypia and proved to lower this risk of breast cancer by 50% or more.

Yet, Degnim said, many women with atypia are not taking the medications, in part because they and their physicians have not had solid estimates of their breast cancer risk to guide them.

Related video: http://newsnetwork.mayoclinic.org/discussion/mayo-clinic-women-with-atypical-hyperplasia-are-at-higher-risk-of-breast-cancer/