Purpose: Ductal lavage provides adequate material and detects atypical cells from ducts in women at increased risk of breast cancer, but the clinical significance of this finding is unclear. We studied the prevalence and predictors of atypia in addition to the proliferation-associated antigen Ki-67 expression in ductal lavage done in women at different risk of breast cancer. Results: Ductal lavage was attempted in 202 women at increased risk and in 16 at average risk. Lavage could not be done in 20 women at increased risk because of anatomic impediments. Seven average-risk women (44%) had samples with inadequate cytology versus 30 women at higher risk (16%; P = 0.014). Atypia was observed in two average-risk women [22%; 95% confidence interval (95% CI), 3-60%]. The prevalence of atypia was 33% in women with a 5-year risk of ≥1.3% according to the Gail model (25 of 75; 95% CI, 23-45%), 36% in women with an increased probability of or ascertained BRCA mutation (9 of 25; 95% CI, 18-57%), and 52% in women with contralateral breast cancer (27 of 52; 95% CI, 38-66%). Ki-67 expression measured in a consecutive series of 80 women at increased risk was higher in atypical samples (P = 0.0001) and was positively associated with total cell count per slide (P = 0.002). Conclusions: Atypia is frequent in women at increased risk of breast cancer but it can also be found in average-risk women. Ki-67 expression is associated with atypia and cell yield and it might be assessed as a surrogate biomarker in early-phase chemoprevention trials.
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