Factors Influencing Stages of Mohs Micrographic Surgery: A Comprehensive Analysis.

BACKGROUND: Mohs micrographic surgery (MMS) achieves high cure rates for basal cell carcinoma (BCC) but may require multiple stages when tumors extend beyond clinically visible margins. Preoperative biopsy subtype information may help identify cases most likely to require additional stages and therefore benefit from adjunctive presurgical imaging. METHODS: In this retrospective single-center cohort of 1541 BCCs treated with MMS, we evaluated clinicopathologic features in relation to first-stage positivity (defined as requiring two or more stages) and to the total number of Mohs stages, using univariate tests and multivariable logistic and negative binomial regression. RESULTS: Four hundred tumors (26%) required two or more stages. First-stage positivity was highest in infiltrative-only tumors (40.7%) and lowest in nodular-only tumors (21.1%). High-risk BCCs with an infiltrative or micronodular component had higher first-stage positivity (29.7%) than low-risk tumors (22.5%). Larger tumors and H-zone location also required more stages. After mutual adjustment, an infiltrative component (odds ratio [OR] 1.50, 95% confidence interval [95% CI] 1.11-2.03), tumor diameter (OR 1.23 per cm, 1.05-1.43) and H-zone location (OR 1.95, 1.26-3.03) remained independently associated with first-stage positivity. CONCLUSIONS: Biopsy-reported histology, tumor size, and anatomic risk zone independently stratify the risk of additional MMS stages and can guide targeted preoperative imaging. Even "low-risk" tumors with superficial components show notable first-stage positivity.