Dr. Susan Love Research Foundation | Most Benign Breast Lumps Don't Increase Breast Cancer Risk

A new study confirms that most women with benign breast lumps have only a slightly increased risk of developing breast cancer over the next 15 years.

The study, "Benign Breast Disease and the Risk of Breast Cancer," appears in the July 21, 2005, issue of the New England Journal of Medicine.

Researchers estimate that one in five women who have a mammogram over the next 10 years will require a biopsy to further investigate a suspicious lump. Waiting for these biopsy results can be agonizing. Yet most of the time women are told they have benign breast disease, not cancer.

To learn more about how frequently women with benign breast disease go on to develop breast cancer, Lynn Hartmann, MD, a professor of oncology at the Mayo Clinic in Rochester, Minnesota, and colleagues followed 9,087 women who had been diagnosed with benign breast disease at the Mayo Clinic for 15 years. To date, 707 of these women have developed breast cancer.

The study found that, overall, women who are diagnosed with benign breast disease are 56 percent more likely to develop breast cancer during the next 15 years. This increased risk is similar to that seen in previous studies on benign breast disease and breast cancer risk.

The researchers also looked more closely at what the biopsy results showed. They found that a woman's risk of developing breast cancer was not the same for all types of benign breast disease. Four percent of the women in the study (336 women) were found to have an increased number of highly abnormal-looking cells, a condition called atypical hyperplasia. These women had a 324 percent greater risk of going on to develop breast cancer than would a woman who did not have benign breast disease. This increased risk is similar to that seen in two other studies.

Thirty percent of the women studied (2,690 women) were found to have cysts that contained a large number of normal cells, a condition called proliferative disease. These women were 88 percent more likely to develop breast cancer over the next 15 years.

Two-thirds of the women studied (6,061 women) were found to have cysts that contained normal-looking cells, a condition called nonproliferative disease. These women were 27 percent more likely than women who did not have benign breast disease to develop breast cancer. But when the researchers looked more closely they found that this increased risk was only true for women with a family history of breast cancer.

This study, like previous studies, found that breast cancer did not always develop in the same breast that had developed benign breast disease. Of the 616 women who later developed breast cancer in one breast, 342 (55.5 percent) developed breast cancer in the breast that was biopsied while 274 (44.5 percent) developed breast cancer in the other breast.

The importance of how the increased risk related to benign breast disease is communicated was underscored in an accompanying editorial by Joann G. Elmore, MD, MPH, a professor of medicine at the University of Washington in Seattle, and Gerd Gigerenzer, PhD, of the Max Planck Institute for Human Development in Berlin.

As Drs. Elmore and Gigerenzer note, the relative risk percentages used in the study are not very easy to understand. A better way to explain the risk, they suggest, is to not use relative risk (a percentage increase or decrease in risk) but to discuss these findings in terms of absolute risk.

Using absolute risk figures, the risk would be explained this way: In a group of 100 women who did not have benign breast disease, 5 of them would be expected to go on to develop breast cancer. In a group of 100 women with nonproliferative breast disease, their 27 percent increased risk would translate into 6 out of 100 of them developing breast cancer. In a group of 100 women who did not have benign breast disease, 5 of them would be expected to go on to develop breast cancer. In a group of 100 women with nonproliferative breast disease, their 27 percent increased risk would translate into 6 out of 100 of them developing breast cancer. In a group of 100 women with proliferative disease, their 88 percent increased risk would translate into about 10 out of 100 women developing breast cancer. And in a group of 100 women with atypical hyperplasia, their increased risk of 324 percent would translate into 19 of 100 women developing breast cancer.

As these numbers illustrate, and as the authors of the editorial note, “The use of relative risks suggests greater effects than truly exist, where the use of absolute risks…prevents this misunderstanding.”

Susan says:

Benign breast disease, also sometimes referred to as fibrocystic breast disease, is very common. The National Cancer Institute estimates that as many as 60 percent of premenopausal women will have benign breast disease at some point in their lives. Benign breast disease isn’t a new type of disease. But it is increasingly more likely to be discovered now that more women are having regular mammograms. (One of the downsides of mammography is that it finds many things that are not breast cancer.)

This study, as have two prior studies, underscores that there is only one type of benign breast disease that is of concern—atypical hyperplasia. The vast majority of women with benign breast disease don’t have atypical hyperplasia. (In this study only 4 percent of the women with benign breast disease had atypical hyperplasia, a rate similar to that seen in other studies.) But when atypical hyperplasia is found, it is important to pay attention to it. As this study and previous studies have found, the presence of atypical hyperplasia is an indicator that a woman may be at increased risk of developing breast cancer in either breast, especially if she has a family history of the disease.

If you are diagnosed with benign breast disease after a biopsy, you should find out what the pathologist saw under the microscope so that you can fully understand what the findings mean. If you are diagnosed as having nonproliferative lesions you have little to worry about, as your breast cancer risk is only 1 percent higher than that of the general population.

If your biopsy shows that you have atypical hyperplasia, you shouldn’t panic. It does not mean that you will develop breast cancer. In fact, most women who have atypical hyperplasia do not develop breast cancer. But you are at higher risk. For that reason, you will want to make sure you undergo regular mammography screening.

You may also want to discuss with your physician the risks and benefits of taking tamoxifen for breast cancer risk reduction. You can learn more about the use of tamoxifen following a diagnosis of atypical hyperplasia here.

If you have atypical hyperplasia and are postmenopausal, you may be eligible to enter the ExCel trial. This trial is the first in the United States to evaluate whether a type of hormone therapy called an aromatase inhibitor is effective in reducing breast cancer risk.

References:

Hartmann LC, Sellers TA, et al. Benign Breast Disease and the Risk of Breast Cancer. New England Journal of Medicine 2005 Jul 21;353(3):229–37.

Elmore JG, Gigerenzer G. Benign Breast Disease—The Risks of Communicating Risk. < a href="http://content.nejm.org/">New England Journal of Medicine 2005 Jul 21;353(3):297–99.