Routine Frozen Section Analysis May Be Omittable for Nodular Basal Cell Carcinoma Undergoing Local Flap Reconstruction.

Background: Intraoperative frozen section analysis (FSA) is commonly used to verify conclusive margins after resection of non-melanoma skin cancer (NMSC) before reconstruction. However, its necessity in nodular basal cell carcinoma (nBCC) remains inconclusive following local flap reconstruction. Methods: Retrospectively, this quality assessment study investigated consecutive patients undergoing FSA-guided excision of nBCC following local flap reconstruction. The study evaluates predictors for free margins after the first FSA. Results: Between 1 January 2024 and 20 January 2025, 112 patients underwent removal of biopsy-verified nBCC followed by local flap reconstruction. Ninety-two patients (82.1%) had conclusive margins on the first FSA with excision margins of 3-5 mm. Of 20 FSA-positive results, 12 were confirmed as true positives on paraffin embedding while eight were false positives, giving FSA a positive predictive value of 60% (12/20); FSA missed residual tumor in four patients (3.6%), corresponding to a sensitivity of 75% and a specificity of 91.7%. Referral biopsy type (punch or curettage) did not significantly affect the accuracy in predicting the BCC subtype, and no demographic, tumor, or location variable was independently associated with margin status. Conclusions: In this study, FSA led to further resection in 20 of 112 cases; however, with a positive predictive value of 60%, it only prevented a second surgery in 10.7% of cases. Because the present analysis is retrospective and lacks oncological follow-up, our findings should be regarded as hypothesis-generating rather than confirmatory: selective omission of routine FSA in well-defined nBCC may shorten the operative time and simplify the workflow but require prospective validation.