False Negative Rate of Sentinel Lymph Node Biopsy on Intraoperative Frozen Section in Early Breast Cancer Patients: An Institutional Experience.

Sentinel lymph node biopsy is an established practice to avoid axillary clearance, in clinically negative axilla, in breast cancer patients. Sentinel nodes harvested by dual technique, if found negative on intraoperative frozen section, can prevent breast cancer patient from a potentially debilitating complete axillary clearance. Hence, analyzing the institutional accuracy of this technique and comparing it with international standards, becomes important in providing optimal treatment to these patients. A retrospective analysis of all patients who had undergone sentinel lymph node biopsy at our institute from December 2014 to December 2018 was carried out. At our institute, sentinel lymph nodes are identified using dual technique of methylene blue and radiocolloid dye. Intraoperative frozen section of these hot or blue or any enlarged nodes is performed. Patients with positive frozen section undergo complete axillary clearance. All frozen and unfrozen biopsy material is subjected to further paraffin sectioning and immunohistochemistry. False negative rate and factors associated with were analyzed. A total number of 424 patients had undergone intraoperative frozen section for the sentinel node in breast cancer at our institute during the study period. Among these, 307 patients had negative sentinel nodes and 117 had positive sentinel nodes of frozen section. Seventeen patients out of 307 had lymph node metastases in final paraffin report (false negative rate = 12.6%). Two of these were found to have macrometastasis, 13 had micrometastasis and 2 had isolated tumor cells on final immunohistochemistry report. Size of metastases to sentinel lymph node was found to be a statistically significant contributor to higher false negative rate. Sentinel lymph node biopsy using intraoperative frozen section, is a sensitive and specific technique of staging axilla in breast cancer patients. Detection of micrometastasis and isolated tumor cells present a technical challenge and are associated with higher false negative rates.