Factors Influencing Accuracy of Sentinel Node Frozen Section for Breast Cancer: A Review of 654 Cases Including 1678 Sentinel Nodes.
Dimple Pandya, Meenakshi Singh, Brian O'Hea, Patricia Farrelly, Martin Burk, Christine Rizk, Carmen Tornos. Stony Brook University Medical Center, NY; Stony Brook University Medicfal Center, NY
Background: Sentinel lymph node biopsy (SLN) is the standard of care for surgical assessment of axillary node status in breast cancer. However the accuracy and methodology of frozen section (FS) is still controversial. The aim of this study was to assess accuracy of FS diagnosis compared to permanent section and identify factors influencing accuracy in a large series of cases treated at our institution.
Design: We identified 654 consecutive cases of SLN biopsies for breast cancer performed at our institution from 1/2006 to 9/2010 that underwent frozen section evaluation, including a total of 1678 SLN. Among these cases there were 65 that had discrepant frozen section diagnosis. The frozen sections and permanent sections of these 65 cases were reviewed. Parameters evaluated included size and location of the metastases in the node, slides containing the metastases (FS, permanent routine, or deeper levels), type of carcinoma (ductal vs lobular), and impact on final stage.
Results: The 65 discrepant cases included a total of 77SLN nodes that were negative on FS and positive on permanent sections, with an overall false negative rate of 4.5%. The discrepant diagnosis were due to sampling error of tumor deposits not present on the FS in 53 nodes (68%), positive cells detected on immumostains only in 19 nodes (24%), and pathologist error overlooking metastases present on the FS in 5 cases (6%). The sampling error was further subclassifed into cases in which the deposits were subcapsularly located and not present on the FS for technical difficulties in cutting tissue close to fat (37 nodes), and cases in which the deposits were clearly deeply located in the node and only seen in deeper sections (15 nodes). Most metastases missed on the frozen section were small ranging from <0.2 to 8.0 mm (mean 1.3mm). The false negative FS had an impact on nodal stage in 45 cases (6.8% of all cases). The FS accuracy rate for ductal carcinoma was 91.2% compared to lobular 79.4%.
Conclusions: False negative frozen sections are predominantly due to technical difficulties in cutting entire nodes including subcapsular areas close to perinodal fat. The accuracy is different for ductal versus lobular carcinomas, and impact on nodal staging is seen in 6.8% of all cases.
Monday, February 28, 2011 1:00 PM
Poster Session II # 28, Monday Afternoon