• breast cancer;
  • sentinel lymph node;
  • molecular assay;
  • one-step nucleic acid amplification assay;
  • frozen section histology;
  • micrometastasis;
  • intraoperative diagnosis



Conventional histopathological examination is limited in measuring accurate total metastatic volume in a lymph node. Recently, a molecular-based procedure to detect lymph node metastases, one-step nucleic acid amplification (OSNA) assay, has been developed. OSNA assay can assess a whole lymph node and yields semiquantitative results. The authors compared the performance in intraoperative detection of sentinel lymph node metastases with OSNA assay using a whole lymph node versus routine frozen section (FS) histology with a 2 mm-sectioned lymph node.


Subjects comprised 531 consecutive patients diagnosed with OSNA assay and 618 consecutive patients diagnosed with FS histological examination. The authors compared the sentinel lymph node-positive rate between the OSNA and FS cohorts, and investigated characteristics of patients for whom OSNA could detect metastases but FS could not. OSNA (+) was defined as micrometastasis, and OSNA (++) and (+I) were defined as macrometastasis.


OSNA assay detected more cases of sentinel lymph node metastases than FS histology (OSNA 121 of 531, 22.8% vs FS 109 of 618, 17.6%; P = .036), particularly micrometastases (46 of 531, 8.7% vs 28 of 618, 4.5%; P = .0064). There was no difference in macrometastasis detection between OSNA and FS (75 of 531, 14.1% vs 81 of 618, 13.1%; P = .68). OSNA detected more metastases than FS in postmenopausal patients (77 of 302, 25.5% vs 43 of 351, 12.3%; P < .0001), and in tumors without fat invasion (23 of 156, 14.7% vs 6 of 151, 4.0%; P = .012) or lymphovascular invasion (67 of 395, 17.0% vs 45 of 458, 9.8%; P = .042).


Intraoperative OSNA assay detects more sentinel lymph node metastases, particularly micrometastases, than does FS histology. OSNA assay can also detect more metastases in postmenopausal patients or from less aggressive primary tumors compared with FS histology. Cancer 2011. © 2011 American Cancer Society.