Sentinel Lymph Node Approach in HER2-Positive and Triple-Negative Breast Cancer with cN0 Status Prior to Neoadjuvant Chemotherapy: Frozen Section or Paraffin Section?

Background Axillary management in breast cancer has shifted significantly with the increasing use of neoadjuvant chemotherapy (NACT), particularly in biologically aggressive subtypes such as HER2-positive breast cancer and triple-negative breast cancer (TNBC). Intraoperative frozen section evaluation of sentinel lymph nodes (SLNs) has traditionally guided axillary dissection, but recent evidence suggests that omitting axillary dissection in patients with minimal or no residual disease provides comparable local control when combined with axillary radiotherapy. This study aimed to evaluate whether intraoperative frozen section or paraffin section assessment affects axillary management in patients who are clinically node negative (cN0) before NACT. Methods This retrospective study included 83 patients with HER2-positive breast cancer or TNBC treated between 2023 and 2025. All patients were clinically and radiologically node negative prior to NACT. SLN biopsy was performed using isosulfan blue, dual technique, indocyanine green, or combinations. Intraoperative frozen section analysis was performed in 59 patients, while paraffin section was used in 24 patients. Clinicopathological features, SLN positivity, pathological response rates, axillary recurrence, and surgical decisions were compared. Statistical analyses were performed using SPSS 18.0, with p < 0.05 considered significant. Results The mean age was 48.2 years. A pathological complete response (pCR) was achieved in 71% of patients, of whom 96.6% had negative SLNs. Among patients with partial response, 75% had negative SLNs. SLN positivity was observed in 8.5% (n = 5) of patients in the frozen section group and 12.5% (n = 3) in the paraffin section group. Axillary dissection was performed only in the frozen section group. No axillary recurrences occurred in either group after a median follow-up of 22 months. Paraffin section evaluation did not result in delayed treatment or increased recurrence. Conclusion In HER2-positive and TNBC patients with cN0 status before NACT and a good pathological response, frozen section analysis of SLNs does not influence surgical decision-making. Paraffin section evaluation represents a safe alternative, reducing operative time, anesthesia exposure, and healthcare costs. These findings support axillary de-escalation in selected high-response subgroups.