Curettage Versus Topical Treatment for Positive Superficial Margins After Mohs Surgery: A Comparative Analysis of Tumor Recurrence

BACKGROUND: Positive margins of squamous cell carcinoma in situ or superficial basal cell carcinoma after Mohs micrographic surgery (MMS) occur in a small but clinically significant proportion of cases, with multiple management options available. OBJECTIVE: This study aimed to compare recurrence-free survival (RFS) across different treatment modalities for positive margins after MMS to inform clinical decision making. METHODS: This was a retrospective cohort study of 422 patients with positive margins after MMS from 2012 to 2022. Recurrence-free survival was analyzed using Kaplan-Meier methodology. Multivariable Cox regression adjusted for age, sex, immunosuppression, tumor characteristics, and anatomic location. RESULTS: Among 388 patients in the primary analysis (306 curettage, 82 topical treatment), 3-year RFS was 92.6% (95% CI: 89.4%-95.9%) for curettage versus 82.7% (95% CI: 73.1%-93.6%) for topical treatment (p=.021). Topical treatment was independently associated with increased recurrence risk (adjusted hazard ratio 2.73, p=.021) after controlling for risk factors. Immunosuppression was the only other significant predictor of recurrence (adjusted hazard ratio 3.04, p = .036). CONCLUSION: Curettage demonstrated superior 3-year RFS compared with topical treatment for positive margins after MMS, with an absolute difference of 9.9%. These findings support curettage as the preferred initial management approach for positive margins after MMS when clinically feasible.