Molecular Detection of Lymph Node Metastases in Breast Cancer Patients: Results of a Multicenter Trial Using the One-Step Nucleic Acid Amplification Assay

Purpose: Accurate assessment of metastasis in sentinel lymph nodes (SLN) of breast cancer is important but involves a heavy workload for the pathologist. We conducted a multicenter clinical trial in Japan to evaluate a new automated assay system for cytokeratin 19 mRNA, the one-step nucleic acid amplification (OSNA) assay (Sysmex), to detect lymph node metastasis of breast cancer. Experimental Design: Surgically obtained axillary lymph nodes were sectioned into four pieces, two of which were examined with the OSNA assay. The other two adjacent pieces were examined with H&E and immunohistochemical staining for cytokeratin 19. Serial sections at 0.2-mm intervals were used in trial 1 to determine the specificity of the OSNA assay, and three pairs of sections cut from the sliced surfaces of the pieces were used in trial 2 to compare the accuracy of the OSNA assay with that of a routine pathologic examination for SLNs in Japan. Results: In trial 1, the sensitivity and specificity were 95.0% [95% confidence interval (95% Cl), 75.1-99.9%] and 97.1% (95% Cl, 91.8-99.4%), respectively, for 124 axillary lymph nodes obtained from 34 patients. In trial 2, the agreement between findings of the assay and of the pathologic examination was 92.9% (95% Cl, 90.1-95.1%) for 450 axillary lymph nodes obtained from 164 patients. Conclusion: The OSNA assay can detect lymph node metastasis as accurately as can conventional pathology and thus can be an effective addition to or alternative for rapid intraoperative examination of SLNs.