Impact of Anatomical Location on Stage Requirements in Mohs Micrographic Surgery: A Retrospective Cross-Sectional Study of 501,209 Cases Using TriNetX (2004–2024)

Objective To analyze the number of stages required for tumor clearance in Mohs micrographic surgery (MMS) by anatomical location and diagnosis. Methods The number of stages required for tumor clearance in Mohs micrographic surgery (MMS) varies by anatomical location and diagnosis. This study analyzed 501,209 MMS cases from the TriNetX database. Cases were categorized using CPT codes (single-stage: 17311/17313, multi-stage: 17312/17314) and linked to anatomical sites via ICD-10 codes. Tumors were stratified into non-melanoma skin cancer subtypes: squamous cell carcinoma in situ, basal cell carcinoma, and squamous cell carcinoma. Results Tumors on the ears required more stages across all subtypes (P<0.00001), as did nasal tumors for BCC (P<0.00001) and SCC (P<0.01). BCC on the eyelids required fewer stages (P<0.00001), while SCC and SCCIS required more (P<0.01, P<0.05). Trunk and extremity tumors generally required fewer stages (P<0.00001), except SCCIS of the upper extremity (P<0.05). SCC and SCCIS of the lips (P<0.01) and scalp/neck (P<0.01) required more stages, whereas BCC at these sites needed fewer (P<0.00001). Conclusions Findings suggest that margin selection, tumor visibility, and risk perception influence MMS stage count. Smaller margins in cosmetically sensitive areas (ears, nose) may increase stage numbers, while broader margins on less visible sites (trunk, extremities) facilitate clearance in fewer stages. Understanding these trends may improve surgical planning and resource management.