BACKGROUND:With the widespread development of genomic analysis, an accurate and quick method for obtaining high-quality nucleic acids is needed. The objective of the current study was to evaluate the quality and potential use of material obtained from fine-needle aspiration cytology (FNAC). METHODS: Ultrasound-or palpation-guided FNAC was performed in 124 consecutive patients who had nodular breast lesions. The authors evaluated the amount of messenger RNA (mRNA) obtained, its quality through the RNA Integrity (RIN) score, and the factors that influenced both. For malignant lesions, the authors attempted to correlate estrogen receptor 1 (ESR1) and HER-2 (c-erb-B2) mRNA expression measured by real-time quantitative polymerase chain reaction with estrogen receptor and HER-2 detection obtained by immunohistochemistry (IHC) and/or fluorescent in situ hybridization (FISH) on the surgical specimen. RESULTS: The amount of mRNA obtained was >1 lg in 89.5% of 124 samples (43 benign lesions and 81 adenocarcinomas). Overall, 59.3% of samples yielded >1 lg RNA with a RIN score >6. The most significant predictors of quality and quantity of mRNA were the cytopathologist who sampled the tumors and a diagnosis of cancer versus benign lesion. The median ESR1 expression level, which was expressed as the polymerase chain reaction cycle threshold (CT) level minus the average 18S value (dct), was 17.7 dct in patients with estrogen receptor-negative tumors and 11.1 dct in patients with estrogen receptor-positive tumors,. The median HER-2 expression level was 15.1 dct in patients with HER-2-negative tumors and 10.7 dct in patients with HER-2-positive tumors. mRNA expression was concordant with the IHC/FISH evaluation in 90.3% of patients for estrogen receptor status and in 98.5% of patients for HER-2 status. CONCLUSIONS: In 70% of cases, FNAC of breast lesions in well trained hands allowed the extraction of mRNA suitable for gene expression analysis. Cancer (Cancer Cytopathol) 2009;117:32-9. V C 2009 American Cancer Society.KEY WORDS: breast cancer, fine-needle aspiration cytology, HER-2, estrogen receptor, gene expression.Fine-needle aspiration cytology (FNAC) or core-needle biopsy (CNB) of the breast can be performed easily on palpable tumors but requires the use of ultrasound (US) guidance for nonpalpable or deep-seated lesions. In some institutions, CNB is preferred, because it allows the study of a piece of tissue by most Original Article pathologists. However, when a trained cytopathologist is present and does the aspiration procedure with an on-site, immediate assessment, FNAC may help the clinician tremendously as a first step in triaging patients and selecting the best candidates for CNB. 1,2 An additional and emerging advantage of FNAC compared with CNB is its ability to obtain high percentages of tumor cells with much lower contamination of stromal cells for molecular analysis.For breast cancer, the use of genomic-based prognostic and predictive factors obtained before surgery is increasing, and a technique that can provide...