Validity of Intraoperative Imprint Cytology and Frozen Section for Sentinel Lymph Node Assessment in Breast Cancer: A Single-Centre Experience.

Background: Sentinel lymph node (SLN) evaluation is central to breast cancer management. Intraoperative touch imprint cytology (TIC) and frozen section (FS) are standard, rapid techniques; however, their performance compared to the gold standard of histopathology in Sri Lanka is underreported. This study evaluates the validity of intraoperative TIC and FS in identifying SLN metastases in patients with breast cancer.

Methods: We retrospectively analysed 416 SLN biopsies (2018-2020), with all cases assessed by TIC, FS, and subsequent paraffin histology. Demographic and clinicopathologic features were correlated with diagnostic metrics.

Results: Mean patient age was 55.9 years. Tumour sizes were ≤20 mm in 23.6%, 21-50 mm in 66.6%, and ≥50 mm in 9.9%. Most cases (92.1%) were invasive carcinoma of no special type (NST). Sensitivity and specificity for TIC were 90.6% and 100%; for FS, 92.7% and 100%. Combined TIC+FS yielded a sensitivity of 92.7% and a specificity of 100%. Detection rates for micrometastases were lower, and sensitivity for TIC was reduced in cases of lobular carcinoma and those where no LVI was found in the primary tumour.

Conclusion:  Both TIC and FS individually showed high sensitivity (90.6% and 92.7%, respectively) and perfect specificity (100%) in the detection of metastatic deposits in SLNs. Combining TIC and FS maintained excellent specificity, while also maintaining the same sensitivity as FS alone. All three methods demonstrated consistently strong predictive values and overall accuracy, with limitations for smaller deposits and specific subtypes, such as invasive lobular carcinoma.