Efficacy of curettage before excision in clearing surgical margins of nonmelanoma skin cancer

Objective: To determine whether curettage before excision of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) improves margin clearance rates. Design: A retrospective, nonrandomized, case-control series of nonmelanoma skin cancers treated with preexcisional curettage followed by simple excision was identified using a computerized search of the database of a dermatopathology service. A validation cohort was established by manually identifying nonmelanoma skin cancers treated with wide excision on a given day. Setting: All analyzed specimens were derived from the Dermatopathology Service at the University of California, San Francisco, a university-based laboratory that provides interpretation of skin biopsy specimens received directly from community (90%) and academic (10%) practices. Patients: Our retrospective cohort consisted of all nonrecurrent nonmelanoma skin cancers diagnosed by biopsy and treated by simple excision between April 1, 1997, and April 30, 1999. There were 1983 BCCs and 849 SCCs included in our study. The validation cohort included skin cancers diagnosed by biopsy treated with simple excision on the 16th day of each month during the same period. Intervention: Preexcisional curettage. Main Outcome Measure: We compared the frequency of tumor margin involvement of curetted vs noncuretted lesions. Margin involvement was considered surgical failure. Results: Forty-two percent of BCCs and 34% of SCCs were curetted before excision. In BCC, risks for surgical failure included head and neck lesions (P<.001), lesions treated by physicians performing fewer than 51 procedures (P<.001), and invasive subtypes (P<.01). Factors associated with surgical failure in SCC included in situ disease (P=.01) and an older (77 vs 74 years) patient population (P=.05). In univariate analysis, curettage before excision decreased the surgical failure rate for BCC by 24% (P=.03) but did not decrease the rate for SCC (P=.8). In multivariate analysis, curettage of BCC reduced surgical failure rates by 26% when the physician performed 50 skin cancer excisions or less during the study (odds ratio, 0.74; 95% confidence interval, 0.57-0.95; P=.02). Conclusion: Preoperative curettage decreases the frequency of positive margins in the management of BCC but not of SCC.