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BACKGROUND: There is a strong need to define the molecular changes in normal at-risk breast epithelium to identify biomarkers and new targets for breast cancer prevention and to develop a molecular signature for risk assessment. Improved methods of breast epithelial sampling are needed to promote whole-genome molecular profiling, increase ductal epithelial cell yield, and reduce sample cell heterogeneity. METHODS: We developed an improved method of breast ductal sampling with ductal lavage through a 22-gauge catheter and collection of ductal samples with a microaspirator. Women at normal risk or increased risk for breast cancer were studied. Ductal epithelial samples were analyzed for cytopathologic changes, cellular yield, epithelial cell purity, quality and quantity of DNA and RNA, and use in multiple downstream molecular applications. RESULTS: We studied 50 subjects, including 40 subjects at normal risk for breast cancer and 37 subjects with non-nipple aspirate fluid-yielding ducts. This method provided multiple 1.0 mL samples of high ductal epithelial cell content (median ≥8 samples per subject of ≥5,000 cells per sample) with 80%-100% epithelial cell purity. Extraction of a single intact ductal sample (fluid and cells) or the separate frozen cellular component provided DNA and RNA for multiple downstream studies, including quantitative reverse transcription- polymerase chain reaction (PCR) for microRNA, quantitative PCR for the human telomerase reverse transcriptase gene, whole-genome DNA amplification, and array comparative genomic hybridization analysis. CONCLUSION: An improved breast epithelial sampling method has been developed, which should significantly expand the acquisition and biomarker analysis of breast ductal epithelium in women at risk for breast cancer. [ABSTRACT FROM AUTHOR]