Background: It is believed that atypical cells identified by nipple duct lavage (NDL) indicate an increased risk for breast carcinoma similar to atypical ductal hyperplasia diagnosed by tissue biopsy, but many basic performance characteristics of NDL currently are undefined.
Methods: NDL was performed in 108 patients unselected for breast carcinoma risk and then was repeated after 2-14 months (median, 8 months) if the initial lavage was classified as atypical. Breast magnetic resonance images (MRIs) were obtained from a subset of patients who had atypical lavage results.
Results: Marked atypia was diagnosed in 22% of 36 breasts with an incident carcinoma compared with 7% of 172 unaffected breasts (P = 0.01). After excluding breasts with an incident carcinoma, there were 32 patients (30%) with either mild or marked atypia. The lavage was repeated in 23 of these women, and the second lavage was classified as atypical in 48%. Neither marked atypia on the initial lavage nor a 5-year Gail risk > or = 1.7% predicted atypia on repeat lavage, but there was a trend for improved reproducibility when the atypia initially was diagnosed in a fluid-producing duct. MRIs were abnormal in 13% of 24 breasts with an atypical lavage, and ductal carcinoma in situ was diagnosed subsequently in 1 breast.
Conclusions: Atypia frequently is diagnosed by NDL, but the reproducibility of repeat lavage is low. Lavage atypia may be physiologic or artifactual rather than pathologic in many instances. Marked atypia occasionally may represent mammographically occult ductal carcinoma in situ.