2010 Annual Meeting Abstracts

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The Accuracy of Intraoperative Frozen Section Analysis of Sentinel Lymph Node Biopsy for Breast Cancer over a Seven-Year Period
*Brigid K Killelea, Baiba J Grube, *Mohammad Rishi, Donald R. Lannin
Yale University, New Haven, CT

Objective: Sentinel lymph node biopsy (SLNB) with intraoperative frozen section (FS) has been accepted for evaluation of the axilla in breast cancer patients. The objective of this study was to determine the false negative rate of FS of the SLN over a 7-year period and to identify the size of metastases, e.g., macrometastases, micrometastases, or isolated tumor cells (ITCs) that were missed on frozen section. The secondary aim was to determine the subsequent axillary management.

Methods: A retrospective review was performed of all patients who underwent SLNB between July, 2002 and December, 2009. Results from FS were compared to the final pathologic diagnosis to characterize false negative findings. The number of patients who underwent axillary lymph node dissection (ALND), as well as the number with additional positive NSLNs was determined.

Results: See tables 1 and 2
Conclusions: FS analysis of the SLN is a highly accurate procedure and resulted in a low false negative rate, and definitive axillary surgery in 99%. The majority of the false negatives were ITCs or micromets, which depending on practice patterns, may not be a clinically important detriment.

Table 1. FS Analysis

	Permanent Results
			Positive	Negative	Total
Frozen Section Analysis	Macromets	micromets	ITCs
Positive	158	9	3	0	170
Negative	8	14	30	746	798
Total	166	23	33	746	968

Table 2. Axillary Management

	no. of cases where ALND was done	no. cases with additional non-SLNs positive	No. cases observed	Total
true positive SN by FS	170/170 (100%)	84/170 (49%)	0	170
False negative FS				52
Macro	6/8 (75%)	1/6 (17%)	2	8
Micro	6/14 (43%)	1/6 (17%)	8	14
ITCs	1/30 (3%)	0	29	30
Total	183		39	222

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