Assessment of Clinical Features of Superficial Basal Cell Carcinomas Treated With Mohs Micrographic Surgery

BACKGROUND: Superficial basal cell carcinomas (sBCCs) are often regarded as indolent, yet their behavior across anatomic sites and Mohs appropriate use criteria (AUC) zones, particularly at nonfacial locations, remains undercharacterized. OBJECTIVE: To characterize discordance, upstaging, and Mohs micrographic surgery outcomes of sBCCs by anatomic location, subsites, and AUC zone. METHODS: Single-center retrospective review of 622 biopsy-confirmed sBCCs treated by Mohs micrographic surgery. Patient demographics, anatomical location, lesion size, Mohs stages, and intraoperative discordance (any nonsuperficial subtype) or upstaging (aggressive subtypes) was analyzed. RESULTS: The mean stages to clearance was 1.82, with a mean defect increase of 2.35 cm2. Head/neck tumors were smaller yet required more stages: 27.9% cleared in 1 stage versus 55.2% (trunk) and 52.2% (extremity) (p < .001). Nearly half of trunk (44.8%) and extremity (47.8%) tumors required 2 or more stages. Discordance was observed in 19.5% of lesions (28.2% head/neck, 13.8% extremity, and 8.4% trunk) and upstaging was observed in 8.4% of lesions, both declining across AUC zones (Area H > M > L; p < .001). The nose had the highest discordance rate (51.8%); upstaged lesions more often required complicated repair (odds ratio 4.21). CONCLUSION: sBCC discordance and upstaging follow an AUC zonal gradient. These data may inform future AUC refinement and patient counseling.