Clinical Versus Histologic Margins for Cutaneous Squamous Cell Carcinoma: Comparing Outcomes for High-Risk Tumors Treated With Mohs Micrographic Surgery.

Background: High-risk cutaneous squamous cell carcinoma (cSCC) is associated with poor clinical outcomes. Traditionally, preoperative clinical tumor size ≥2 cm, based on Brigham and Women's Hospital (BWH) staging criteria, is high risk.

Objective: To compare outcomes of cSCC treated with Mohs micrographic surgery (MMS) with a preoperative size ≥2 cm (clinically ≥2 cm) versus cSCC with preoperative size <2 cm and postoperative defect size ≥2 cm (histologically ≥2 cm).

Methods: Prospective data were collected from January 1, 2014, to December 31, 2020, on MMS cases for cSCC with a preoperative and/or postoperative size ≥2 cm. Clinical outcomes were followed until March 15, 2023. Data were analyzed using multivariate regression.

Results: Three hundred thirty cases of MMS for cSCC were included. Cutaneous squamous cell carcinoma clinically ≥2 cm occurred more frequently in elderly patients; cSCC histologically ≥2 cm were more commonly located in the H region, required wider surgical margins, and more MMS stages to achieve clearance. There were no significant differences in rates of recurrence and metastasis between the groups.

Conclusion: These data suggest that postoperative (histologic) MMS defect size may allow for better risk stratification of high-risk cSCC and improved staging of cSCC.