A new study has reported that women at high risk for breast cancer are more likely to develop benign breast disease, which is more likely to progress to breast cancer at a younger age than in the general population. Benign breast disease is a known risk factor for breast cancer, with the highest risk found among women with atypical proliferative subtypes. Atypical hyperplasia is associated with a 20% to 50% increase in risk of invasive breast cancer in the general population. This increased risk has been shown to persist at least 25 years after a diagnosis of atypical hyperplasia. However, little information is available regarding the prevalence and characteristics of benign breast disease among women at high risk for breast cancer. The study included women participating in an ongoing prospective study of women with a family history of breast cancer (with or without a BRCA1 or BRCA2 mutation) who attend the Breast and Ovarian Surveillance Service at Johns Hopkins. A total of 575 of the 953 women in the program had reported having at least one breast surgical procedure at the time of enrollment. 66% of the women had two or more relatives with breast and/or ovarian cancer.

During the follow-up period, 257 breast cancer cases and 170 new cases of benign breast disease were found. An 18% rate of new cases of biopsy-proven benign breast disease was observed, with a median age at diagnosis of 44.2 years. The incidence of breast cancer on first biopsy was 27%, with a median age of 46.9 years. With respect to the benign breast disease cases, 58% were found to be non-proliferative, 27% were proliferative non-atypical lesions, and 15% were atypical hyperplasia. The median age at benign breast disease diagnosis was significantly higher among those with proliferative (46.8 years) compared to non-proliferative benign breast disease (41.4 years). 26.5% of those diagnosed with benign breast disease developed breast cancer within a median of six years (range: 0 to 31 years). Atypical hyperplasia progressed to breast cancer significantly more often (44%) than non-proliferative disease (16.3%) within 10 years of diagnosis of benign breast disease. The authors conclude that a high incidence of atypical hyperplasia subtypes at a young age occurred in this high-risk population. A significant proportion of these women subsequently developed breast cancer in a relatively short period of time compared to what has been reported in the general population.