Abstract P3-03-16: Intraoperative evaluation of sentinel lymph nodes after neoadjuvant systemic therapy in breast cancer
Authors: Sahoo S , Mir M , Sarode V , Fang Y , Peng Y , Gwin K , Hwang H 
Published: May 2019

Abstract
Introduction:
Intraoperative evaluation of sentinel lymph nodes (SLN) in breast cancer patients are performed using Touch preparation (TP) and/or frozen section (FS). Touch preparation for intraoperative evaluation of SLN is quick and known to be a highly sensitive and specific method for detection of metastasis. Detecting metastases in SLN intraoperatively can be challenging in patients who receive neoadjuvant systemic therapy (NST). In our hospitals, we have been routinely evaluating SLN intraoperatively in patients who have undergone (NST), including those with known metastasis to an axillary lymph node (LN) prior to therapy.
Objective:
To compare the sensitivity and specificity of TP and frozen section (FS) in the intraoperative evaluation of SLN in the neoadjuvant setting.
Material and Methods:
This retrospective review study was approved by the institutional review board. Four hundred ninety-eight SLN from 142 patients were included in this study. The intraoperative results for TP and FS were compared with the final pathology results. Relevant clinical and pathological findings such as type of surgery, tumor grade, histologic subtype, and size of metastasis were reviewed.
Results:
Of the 498 SLN evaluated intraoperatively, 341 were by TP only, 57 by FS only and 100 by both.
Of the 341 SLN examined by TP only, 313 (92%) were interpreted as negative and 28 (8%) as positive for carcinoma intraoperatively. Eighteen LN turned out to be false negative (FN) with no false positives (FP) (sensitivity=62%, specificity=100%). In the false negative cases, 12 LN had micrometastasis, 6 macrometastasis and 1 showed isolated tumor cells (ITC). The size of the macrometastatic ranged from 3 mm to 10 mm.
Of the 57 LN examined by FS only, 48 were true negative and 9 were true positive (sensitivity=100%, specificity=100%).
Of the 100 LN evaluated by both TP and FS, 59 were interpreted as negative and 41 as positive for carcinoma. There were 8 false negatives and 1 false positive (sensitivity=83%, specificity=98%). Of the 8 false negatives, 7 showed micrometastasis and 1 LN had ITC.
Discussion:
In neoadjuvant cases, both the primary tumor as well as lymph node metastases can show therapy effect such as fibrosis, necrosis and/or histiocytic aggregates. Evaluating SLN in NST cases can be challenging secondary to these effects. The TP slides are often paucicellular in SLN with treatment effect. Residual tumor cells are often trapped in a fibrotic scar and do not transfer onto the TP slide leading to low sensitivity. Therefore, for optimal intraoperative evaluation of SLN in NST cases, frozen section with or without touch preparation, is recommended.
Citation Format: Sahoo S, Mir M, Sarode V, Fang Y, Peng Y, Gwin K, Hwang H. Intraoperative evaluation of sentinel lymph nodes after neoadjuvant systemic therapy in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-16.