Prognostic significance of benign proliferative breast disease

Background. Recent studies concerning an association between benign breast diseases and risk of subsequent breast cancer have focused on benign proliferative lesions recognized in biopsy specimens. Some have implicated atypical hyperplasia as being associated with the greatest risk. Methods. The histologic sections of specified benign breast lesions from 1799 women were reviewed and reclassified, using published criteria for proliferative disease. Prognostic significance was assessed by relating the pathologic findings to the development of breast cancer observed during an average 21 years of follow‐up, in which time 157 women developed the disease. Results. Benign proliferative changes were recognized in 85% of the patients, with a corresponding relative risk of subsequent carcinoma equal to 2.2 times population rates (95% confidence limits, 1.9 and 2.6). Increasing levels of hyperplasia and atypia in lobules or ducts were associated with modest increases in risk, ranging from 2.1 to 2.3 to 3.0 for proliferative changes with no atypia, mild atypia, and moderate to severe atypia, respectively. This trend was not statistically significant. The most significant risk indicators in this study were the presence of adenosis (relative risk, 3.7), and moderate or severe atypia in ducts (relative risk, 3.9). Conclusions. Benign proliferative breast disease recognized in biopsy specimens is associated with an increased risk of future breast cancer, but fine distinctions among levels of hyperplasia and atypia did not significantly distinguish risk among patients in this study.