False-negative frozen section of sentinel nodes in early breast cancer (cT1-2N0) patients

Diagnostic accuracy and challenges of intraoperative frozen section evaluation for axillary sentinel lymph node biopsy and breast margins

AIMS

Our study aims to audit and evaluate the accuracy and pitfalls of intraoperative evaluation of frozen sentinel lymph nodes (IOE-FSLN) and resection margins (IOE-FSM) compared to final findings in paraffin sections.

METHODS

A total of 264 cases underwent intraoperative evaluation, encompassing 688 sentinel lymph nodes (SLNs) and 1186 surgical margins. Frozen section (FS) diagnoses were compared with corresponding permanent sections of FS (PFS). Sensitivity, specificity, false-negative rate, false-positive rate, and concordance rates were assessed. Cases with discrepancies underwent a detailed histological review.

RESULTS

The study predominantly comprised cases of invasive breast carcinoma (IBC) (74%). For FSLN reporting, sensitivity was 88.1%, specificity 100%, and FS-PFS concordance 99.0%. FSM reporting showed sensitivity of 85.0%, specificity 99.9%, and concordance 98.4%. Sampling errors accounted for 86% (FSLN) and 88% (FSM) of discrepancies, with interpretive errors present in 1/7 FSLN and in 2/17 FSM cases. The shave margin method demonstrated a higher false-negative rate in FSM reporting. The rate of final positive margins was reduced from 21.3% to 11.4% when IOE-FSM was utilized.

CONCLUSION

IOE-FSLN and IOE-FSM showed high reliability in guiding intraoperative decisions for axillary lymph node dissection and achieving free surgical margins in one-stage surgeries. However, limitations include challenges in distinguishing metastatic carcinoma from benign mimics in FSLN and diagnosing certain features such as IBC with post-treatment changes, invasive lobular carcinoma in FSLN and FSM; IBC rich in tumour-infiltrating lymphocytes, low-grade (DCIS/IBC in FSM) without immunohistochemical studies.

Is Routine Intraoperative Frozen Section Analysis of Sentinel Lymph Nodes Necessary in Every Early-Stage Breast Cancer?

Purpose

Clinical application of the ACOSOG Z0011 trial results allows clinically node-negative breast cancer patients who meet criteria to avoid axillary dissection even when 1–2 sentinel lymph nodes (SLNs) are positive for metastatic disease. Intraoperative frozen section (iFS) analyses of SLNs were thought to reduce re-operation rates despite variable reported sensitivity and possibility of a false negative result. This study evaluated the rate of re-operations prevented by SLN iFS in a tertiary care hospital in Bangkok, Thailand, over a 6-year time-frame.

Patients and Methods

From April 2016 to April 2022, 1284 sentinel lymph node biopsy (SLNB) procedures were performed. Of these, 214 cases were breast-conserving surgery in accordance with the ACOSOG criteria with concomitant usage of iFS. Clinicopathological features of these cases were collected and analyzed. Re-operation rates prevented by the additional intervention were reported.

Results

Only five additional operations were prevented with the usage of 214 iFS. The discordance rate between frozen and permanent sections in terms of presence of metastatic disease and number of total lymph nodes was around 15%. Tumor staging, node staging, Nottingham histologic grading and lymphovascular invasion are significant predictors of SLN metastasis.

Conclusion

iFS results in a very low prevention rate for follow-up ALND in patients with preoperative clinically negative axillary nodes and is associated with a non-negligible discordance rate with permanent sections. Our study suggests iFS may be avoided in most cases of early-stage clinically and radiographically node-negative breast cancer patients. Doing so may reduce surgical costs and total operative time without a significant impact on the overall quality of treatment and standard of care.