Accuracy of Frozen Section Analysis of Sentinel Lymph Nodes for the Detection of Asian Breast Cancer Micrometastasis - Experience from Pakistan

Background: Intraoperative sentinel lymph node biopsy has now become the standard of care for patientswith clinically node negative breast cancer for diagnosis and also in order to determine the need for immediateaxillary clearance. Several large scale studies confirmed the diagnostic reliability of this method. However,micrometastases are frequently missed on frozen sections. Recent studies showed that both disease free intervaland overall survival are significantly affected by the presence of micrometastatic disease. The aim of this studywas to determine the sensitivity and specificity of intraoperative frozen section analysis of sentinel lymph nodes(SLNs) for the detection of breast cancer micrometastasis and to evaluate the status of non-sentinel lymph nodes(non-SLNs) in those patients subjected to further axillary sampling. Materials and
Methods: We performeda retrospective study on 154 patients who underwent SLN biopsy from January 2008 till October 2011. TheSLNs were sectioned at 2 mm intervals and submitted entirely for frozen sections. Three levels of each sectionsubmitted are examined and the results were compared with further levels on paraffin sections.
Results: Overall40% of patients (62/154) were found to be SLN positive on final (paraffin section) histology, out of which 44demonstrated macrometastases (>2mm) and 18 micrometastases (<2mm). The overall sensitivity and specificityof frozen section analysis of SLN for the detection of macrometastasis was found to be 100% while those formicrometastasis were 33.3% and 100%, respectively. Moreover 20% of patients who had micrometastases inSLN had positive non-SLNs on final histology.
Conclusions: Frozen section analysis of SLNs lacks sufficientaccuracy to rule out micrometastasis by current protocols. Therefore these need to be revised in order to pick upmicrometastasis which appears to have clinical significance. We suggest that this can be achieved by examiningmore step sections of blocks.