Characteristics of Breast Ducts in Normal-Risk and High-risk Women and Their Relationship to Ductal Cytologic Atypia.

Breast ductal cytologic atypia is an important risk factor for sporadic breast cancer. Characterization of the associated normal breast tissue is needed to develop additional methods of risk assessment and new targets for breast cancer prevention. We conducted a prospective clinical trial evaluating women at normal-risk or at high-risk for sporadic breast cancer. Breast ductal cells were collected and studied cytologically and by gene expression profiling, and breast ductal architectural changes were studied by breast ductal endoscopy (BDE) and breast MRI. One hundred and forty subjects were studied, 70 at high risk (RR, 2.0-4.6) and 70 at normal risk. Cytologic atypia was present in 22.9% of high-risk and 25.7% of normal-risk subjects. Ductal endoscopy was performed in 89 subjects and revealed benign intraductal abnormalities, primarily intraductal fibrous webbing suggesting chronic inflammation, in 40.4% of high-risk and 5.4% of normal-risk subjects, respectively (P 2 = 0.0002). Two high-risk subjects with atypia and no normal-risk subjects with atypia developed invasive breast cancer. Gene expression profiling of ductal cells showed comparable gene expression profiles without enriched expression of previously defined oncogenic signatures in subjects with cellular atypia compared with those without atypia, and in high-risk subjects compared with normal-risk subjects (FDR > 0.5). Cytologic ductal atypia in normal-risk subjects does not appear to be of clinical significance. Atypia in women at high risk may be associated with benign and malignant breast ductal abnormalities; these characteristics of high-risk ductal cells may not be reflected in gene expression profiles. ©2020 American Association for Cancer Research.