Benign breast disease is a term that describes changes to breast tissue that are not cancerous. Some common benign breast conditions include fibrocystic changes, benign tumors, and inflammation.

Although benign breast conditions are not themselves life-threatening, some of these conditions have been shown to increase the risk for breast cancer . But important questions remain unanswered. For example, to what extent do different types of benign breast changes increase breast cancer risk? Does family history contribute to this increased risk? Is age at diagnosis of the benign breast condition important?

In a study published in the July 21, 2005 New England Journal of Medicine , researchers followed more than 9,000 women with benign breast disease for an average of 15 years. They found that certain types of benign breast disease, a family history of breast cancer, and younger age at diagnosis of benign breast disease were all important risk factors for a subsequent diagnosis of breast cancer.

About the Study

The researchers identified 9,087 women who had had a benign breast lesion surgically removed between 1967 and 1991. These women were asked about family history of breast cancer, age at the time of the benign breast disease diagnosis, and any subsequent occurrence of breast cancer.

Stored biopsy samples of the benign breast lesions were available for all participants. Based on a microscopic examination of these tissue samples, the participants’ breast disease was classified into one of the following categories:

Nonproliferative fibrocystic changes (fibrous tissue or fluid-filled cysts)

Proliferative fibrocystic changes without atypia (an overgrowth of certain normal-appearing breast cells)

Proliferative fibrocystic changes with atypia (an overgrowth of certain breast cells which appear large or otherwise abnormal under the microscope)

The researchers followed the patients from the day the benign lesion was biopsied until the date of a breast cancer diagnosis, death, or last contact. The average follow-up was 15 years.

The researchers compared the risk of breast cancer in these patients with the risk in an average population—the latter based on the Iowa Surveillance, Epidemiology, and End Results (SEER) registry, an extensive collection of cancer incidence and survival data.

The Findings

Of the 9,087 women in the study, 6,061 (66.7%) had nonproliferative changes, 2,690 (29.6%) had proliferative changes without atypia, and 336 (3.7%) had proliferative changes with atypia.

During the follow-up period, 707 women developed breast cancer. Based on the SEER registry, 453 women would have been expected to develop breast cancer. Therefore, a diagnosis of benign breast disease increased the risk of breast cancer by 56%. The excess risk persisted for at least 25 years after the initial biopsy.

The type of benign breast disease was a major indicator of breast cancer risk. Compared to the SEER population, women with nonproliferative changes were 27% more likely to develop breast cancer; women with proliferative changes without atypia were 88% more likely to develop breast cancer; and women with proliferative changes with atypia were 424% (more than four times) as likely to develop breast cancer.

Family history was identified as an independent risk factor. Compared to the SEER population, women with a strong family history (one first-degree relative with breast cancer before age 50, or two or more relatives with breast cancer with at least one being a first-degree relative) were at a 93% increased risk; women with a weak family history (any degree of family history less than strong) were at a 43% increased risk, and women with no family history were at an 18% increased risk. Importantly, for women with nonproliferative changes and no or weak family history, there was no increased risk of breast cancer.

The researchers also found a significant correlation between the diagnosis of proliferative changes with atypia and age at the time of this diagnosis. Women less than 45 were seven times more likely to develop breast cancer than women in the SEER population. Women diagnosed between age 45 and 55 were five times more likely and women diagnosed after age 55 experienced only 3.37 times the risk.

This study had some important limitations. First, although this study presents family history as an independent risk factor, information on family history was only available for 53% of the study participants. In addition, the study lacks adequate data on other potentially important risk factors such as breast density and menopausal status.

How Does This Affect You?

This study found that certain types of benign breast disease can increase the risk of breast cancer, and that family history and age at diagnosis may further influence this risk. The good news was that the majority of women had nonproliferative changes, and that these women—particularly those with no family history of breast cancer—did not have an increased risk.

In 1997, the National Cancer Institute issued a recommendation urging all women aged 40 and older to have a screening mammogram every one to two years. As a result, the number of women having mammograms has increased, and with it, the number of breast biopsies, many of which result in the identification of benign breast disease.

With this study, physicians should be better equipped to tell women with benign breast disease whether they fall into a high- or low-risk group for breast cancer. This is an important advancement because degree of risk can help women and their physicians decide on appropriate follow-up. Women at low risk, for example, might be advised to continue having annual or biannual mammograms, while women at high risk might consider more frequent screening. Women as very high risk may even be advised to take a drug like tamoxifen, which can lower the risk of breast cancer.