The accuracy of intraoperative frozen section examination of sentinel lymph nodes in squamous cell cancer of the vulva.

OBJECTIVE: To assess the diagnostic accuracy of intraoperative pathologic examination of sentinel lymph nodes (SLNs) and patient outcomes in vulva cancer.

METHODS: This retrospective study included patients with unifocal, <4 cm, invasive vulvar squamous cell carcinoma and clinically negative groin nodes treated with SLN biopsy from January 2008-March 2020. Intraoperative SLN frozen section and final pathology were compared. If the SLN was negative, inguinal femoral lymphadenectomy (IFLD) was omitted. Recurrence location and groin recurrence free survival (RFS) were assessed.

RESULTS: The SLN cohort included 173 patients, with 258 groins. On frozen section, there were 36/258 positive and 222 negative groins. On final pathology, there were 39/258 positive: 31 macrometastases, 6 micrometastases, 2 isolated tumor cells (ITCs) and 219 negative groins. The sensitivity, specificity, PPV and NPV for intraoperative detection of metastatic disease, was 89.7% and 99.5%, 97.2% and 98.2%, respectively. There was 1 false positive and 4 false negative frozen section results where final pathology revealed 2 ITCs, 1 micrometastasis and 1 macrometastasis. Based on intraoperative results, thirty patients (17.3%) underwent immediate IFLD. Median follow up was 38.0 (1-137.8) months. The 3-year groin RFS was 91.6% (95% CI 86.2-97.4%) for negative SLNs and 64.6% (95% CI 46.5-89.7%) for positive SLNs on frozen section. Similarly, the 3-year groin RFS was 91.7% (95% CI 86.3-97.4%) for negative, 58.4% (95% CI 38.5-87.7%) for macrometastases and 100% for micrometastases/ITCs on final pathology.

CONCLUSIONS: Intraoperative assessment of SLNs is accurate to determine need for IFLD and does not compromise patient outcomes in vulvar cancer.