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21053 Background: Sentinel lymph node metastasis in breast cancer patients has conventionally been determined by intra- operative histopathological examination of frozen sections followed by definitive post-operative examination of permanent sections. The purpose of this study is to evaluate a more efficient method for intra-operative detection of lymph node metastasis in a clinical setting. Therefore, a new rapid method of detection of CK19 mRNA by One Step Nucleic Acid Amplification (OSNA) and Reverse Transcription Loop Mediated Isothermal Amplification (RT-LAMP) was tested against standard histological techniques. Methods: The clinical study was conducted at two facilities using 188 lymph nodes (46 patients). Lymph nodes from axillary dissected patients with breast cancer were divided into four slices. Alternate slices were used for the new method of CK19 mRNA detection (OSNA) and histopathological examination by hematoxylin & eosin and cytokeratin staining. For the analysis of concordance between both methods, the slices for histopathology were cut in 4 μm sections. For the OSNA method the other 2 slices were homogenised in a short sample preparation step. Afterwards CK19 mRNA was directly amplified from the tissue lysate within 16 minutes. Results: In the clinical study, an overall concordance rate between the OSNA assay and histopathology was 92%. Several discordant results are explainable with the expected uneven distribution of metastases within the lymph nodes. Conclusions: The study indicates that OSNA is a reliable and fast diagnostic tool for the detection of lymph node metastases in breast cancer patients. This method could be beneficial to avoid diagnostic delay for the patient or second surgery based on a post-operatively diagnosed positive lymph node. No significant financial relationships to disclose.

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