609 Background: The aims of the study were 1) to assess the accuracy of a new intra-operative molecular diagnostic tool named OSNA, based on the measurement of cytokeratin 19 (CK19) mRNA, in the detection of axillary sentinel lymph node (SLN) metastases in patients with breast carcinoma 2) to determine the concordance of OSNA analysis with multilevel haematoxylin and eosin (H&E) and immunohistochemical (IHC) examination. Methods: A prospective series of 247 consecutive SLNs from 187 breast cancer patients was evaluated. The OSNA assay (Sysmex, Kobe - Japan) follows a short sample preparation step and subsequent rapid amplification of CK19 mRNA based on reverse transcription loop-mediated isothermal amplification. Each SLN was immediately divided into four slices. Two alternate slices were used for the intra-operative OSNA assay. The remaining two slices were investigated by six-level histopathology with 100 μm skip ribbons using routine H&E and CK19 IHC staining. The results of histology and OSNA were then compared. Results: Pts characteristics: infiltrating ductal/infiltrating lobular/mucinous/medullar/DCIS: 130/10/1/1/25. OSNA and histo-pathological methods identified 54 SLNs positive and 185 negative cases (2/3 contained isolated tumour cells). We found 8 discordant cases, 2 OSNA negative with micrometastasis found by IHC/H&E analysis, 5 OSNA positive for micrometastases but IHC/H&E negative and 1 case macrometastatic at OSNA, while negative at IHC/H&E analysis. The overall concordance of OSNA with histopathology was 96.7% with a specificity of 96.8% and sensitivity of 96.4%. These discordances could be due to sampling bias such that a micrometastasis was confined to the slices used for OSNA or the slices used for histology. Conclusions: The current study suggests that the performance provided by OSNA assay is comparable to intensive histopathological work-up even when using only half a lymph node. The method could be applied as a rapid and reliable intra-operative diagnostic tool thus preventing breast cancer patients from a diagnostic delay or second surgery due to a postoperatively diagnosed positive SLN. No significant financial relationships to disclose.
Peer Review #3 of "A new molecular diagnostic tool for surveying and monitoring Triops cancriformis populations (v0.1)"
