Researchers say decrease in the use of postmenopausal hormone therapy has simultaneously led to the reduction in the incidence of atypical ductal hyperplasia.
Previous studies have shown that women who are diagnosed with atypical ductal hyperplasia are at a three- to five-fold increased risk of developing breast cancer.
"Postmenopausal hormone treatment is associated with increased rates of benign breast biopsies, and early and late stages of cancer," said Dr Tehillah Menes, who was the chief of breast service in the Department of Surgery at Elmhurst Hospital Centre, New York, when this study was conducted.
"Atypical ductal hyperplasia is associated with the use of postmenopausal hormone treatment and its rates have decreased with the decline in use of this treatment," Menes added.
During the study, researchers examined the rates of atypical ductal hyperplasia to determine risk factors and rates for more than 2.4 million mammography studies with and without breast cancer.
They found that between 1996 and 2005 postmenopausal hormone therapy use decreased from 35 percent to 11 percent, followed by a decrease in atypical ductal hyperplasia from 5.5 per 10,000 mammograms in 1999 to 2.4 in 2005.
The cases of atypical ductal hyperplasia associated with cancer reached a peak of 4.3 per 10,000 mammograms in 2003, but decreased to 3.3 in 2005.
"The rate of atypical hyperplasia declined, which we didn't expect to see with the increased use of mammography to identify abnormal lesions," said researcher Dr Karla Kerlikowske, professor of medicine and epidemiology and biostatistics, University of California, San Francisco.
"We did not expect to find a decline in rate of atypical ductal hyperplasia with a decline in postmenopausal hormone treatment use," Kerlikowske added.
"These findings help clarify the different pathways to the development of breast cancer and the role of postmenopausal hormone treatment in increasing the rates of breast cancer," Menes added.
The findings are published in Cancer Epidemiology, Biomarkers and Prevention.