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% CI), 75.1-99.9%] and 97.1% (95% CI, 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% CI, 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.