Intraoperative Imprint Cytology Versus Frozen Section for Sentinel Lymph Node Assessment in Breast Carcinoma: A Prospective Diagnostic Accuracy Study From a Resource-Limited Setting in Eastern India.

Background Reliable intraoperative assessment of sentinel lymph nodes (SLN) is critical for surgical decision-making in breast carcinoma. Frozen section (FS) is the standard intraoperative method, but requires cryostat infrastructure that is unavailable in many centers across eastern India. Imprint cytology (IC) is an inexpensive, tissue-preserving alternative; however, locally relevant prospective data to support its use as a standalone intraoperative test have been lacking. Aim To compare the diagnostic accuracy of intraoperative IC and FS for SLN evaluation in breast carcinoma, using permanent paraffin histopathology as the reference standard, and to determine whether IC is non-inferior to FS as an intraoperative diagnostic method. Methodology A prospective cross-sectional study was conducted over 18 months at a government tertiary care center in Jharkhand, India. A total of 109 consecutive female patients (aged 30-75 years) with histologically confirmed breast carcinoma undergoing sentinel lymph node biopsy (SLNB) were enrolled. Each SLN was evaluated intraoperatively by IC followed by FS; permanent paraffin-section histopathology served as the reference standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), overall accuracy, and the area under the receiver operating characteristic curve (AUC), with 95% confidence intervals (CIs), were calculated. Inter-method agreement was evaluated using McNemar's test and Cohen's kappa coefficient. Results Of 109 SLNs, 61 (56.0%) were positive for metastasis on final histopathology. IC yielded a sensitivity of 86.9% (95% CI: 76.2%-93.2%), specificity of 100%, and overall accuracy of 92.7%; FS yielded a sensitivity of 88.5% (95% CI: 78.2%-94.3%), specificity of 100%, and accuracy of 93.6%. The AUC was 0.934 for IC and 0.943 for FS; DeLong paired comparison demonstrated no statistically significant difference (P > 0.05). Inter-method concordance was 99.1%, with a Cohen's kappa of 0.982 (P < 0.001). All patients had received NACT; false-negative results for both methods involved small residual metastatic deposits showing post-treatment change. Conclusions IC demonstrated diagnostic performance statistically non-inferior to FS for intraoperative SLN assessment in breast carcinoma. Given its lower cost, shorter preparation time, complete tissue preservation, and independence from cryostat infrastructure, IC is a valid, evidence-based, and independently deployable intraoperative modality for resource-limited settings.