In breast cancer, the number of lymph node metastases is the strongest predictor of outcome. However, histopathology may underestimate the frequency of metastasis. Here we compare automated molecular detection of cytokeratin 19 mRNA by one-step nucleic acid amplification (OSNA) with histopathology of single tissue sections for the staging of axillary lymph nodes in patients with breast cancer. Axillary lymph nodes were collected from 55 patients with primary breast cancer and sentinel lymph node (SLN) metastases. The central 1-mm portion of each node was processed for hematoxylin-eosin staining, and the remaining tissue was analyzed by OSNA. According to OSNA, histopathology misclassified 41.8% of patients as negative for axillary node metastasis (P=0.007). Of the individual nodes considered negative by histopathology, 4.5% contained micrometastases and 2.5% contained macrometastases according to OSNA. Furthermore, 80% of micrometastases identified by histopathology were reclassified as macrometastases by OSNA. Histopathology failed to identify 81.1% of nodes shown to contain metastasis by OSNA. However, OSNA yielded no false-negative results. On the basis of OSNA results, 3 patients were reclassified to a higher pathologic stage. The number of SLN and non-SLN metastases was unrelated according to OSNA (P=0.891). These results show that, compared with molecular detection, histopathology of single tissue sections significantly underestimates the frequency of axillary node metastases. We discuss the implications of these findings in light of current recommendations on the staging of breast cancer.

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Monoclonal therapies could represent baseline-personalized medicine for patients with neoplasia. One of the most successful examples is Trastuzumab, a humanized antibody against epidermal growth factor receptor 2. Human epidermal growth factor receptor 2 (HER2) is a trans-membrane tyrosine kinase coded by the gene HER2/neu and overexpressed in approximately 12% to 20% of infiltrating breast carcinomas. The overexpression of HER2 is an independent adverse prognostic factor in relation to survival and is also predictive of response to treatment. Therefore, the correct evaluation of HER2 status is essential for the management of infiltrating breast carcinoma to determine the response to Trastuzumab. The most common evaluation technique is immunohistochemistry, which is confirmed by fluorescent or chromogenic monochrome or dual-gene in situ hybridization in ambiguous cases (immunohistochemical 2+). Our objective was to evaluate the diagnostic value of a new technique on the basis of HER2 mRNA in situ hybridization (HistoSonda) and study its correlation with immunohistochemistry and dual-chromogenic in situ hybridization (DUO-CISH) in 403 cases of infiltrating breast carcinoma. The percentage of DUO-CISH amplification was 25.8%, HistoSonda positivity was 31.2%, and positivity for Hercep-Test was 48.1%, including (+2) and (+3). Comparisons were made of each of the techniques, HistoSonda to IHQ and HistoSonda to DUO-CISH. The overall concordance between DUO-CISH and HistoSonda was 89%. Our data support the consistency of HistoSonda as a useful tool to determine HER2 status in breast cancer.

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