Molecular analysis of nipple fluid for breast cancer screening

Lack of sensitivity and specificity of image-based breast cancer screening has urged the exploration of alternate screening modalities. Nipple fluid, which contains breast epithelial cells, is produced in small amounts in the breast ducts of nonlactating women and can be collected by noninvasive vacuum aspiration. After administration of nasal oxytocin, nipple aspiration yields sufficient material for molecular analysis in the large majority of women. Whereas nipple fluid cytology appears to have only a moderate correlation with breast cancer development, methylation holds promise as a more appropriate biomarker, since methylation aberrations occur as an early and frequent event during carcinogenesis. Using quantitative multiplex methylation-specific PCR, methylation can be detected in minute amounts of DNA extracted from nipple aspirates, precluding the need for more invasive intraductal approaches such as ductal lavage and random periareolar fine needle aspiration. The application of genomic and proteomic diagnostics to nipple aspirates therefore provides unprecedented opportunities for early breast cancer diagnosis amendable to population-based screening.