Background: The one-step nucleic acid amplification (OSNA) method can assess the expression level of cytokeratin 19 mRNA in sentinel lymph nodes in breast cancer. We compared the time required for diagnosis and concordance of results between the OSNA method and conventional intraoperative pathological examination. We then examined the relationship between the frequency of non-sentinel lymph node metastasis and (1) the expression level of CK19 mRNA in the sentinel lymph nodes and (2) clinico-pathological features of the primary tumor.
Methods: In the comparison study, pairs of sentinel lymph node sections from 53 consecutive patients were examined: one section by hematoxylin-eosin staining and the other by OSNA assay. The latter involved reverse-transcription loop-mediated isothermal amplification of cytokeratin 19 mRNA, assessed quantitatively. In the second phase, 306 sentinel lymph nodes were removed from 248 consecutive patients, and whole sentinel lymph nodes were examined by OSNA assay alone.
Results: OSNA assay was a little more time-consuming than conventional pathological diagnosis (34-45 vs. 22-25 min, p < 0.0001). Concordance between the two methods was 93%. The frequency of non-sentinel lymph node metastasis (p < 0.0001) and the total number of lymph node metastases (p < 0.0001) increased with the amount of cytokeratin 19 mRNA on OSNA assay. We found no significant relationship between the amount of cytokeratin 19 mRNA in sentinel lymph nodes and breast cancer immunohistochemical subtype.
Conclusions: The OSNA method is suitable to detect sentinel lymph node metastasis and to predict the possibility of non-sentinel metastasis. This semi-automated quantitative analysis system reduces the burden on pathologists.