Risk factors associated with tumor upstaging in melanomas treated with Mohs micrographic surgery with melanocytic immunohistochemistry

Background: Mohs micrographic surgery with melanocytic immunohistochemistry (MMS-I) is increasingly utilized for special site melanoma treatment. Yet, frequency and risk factors associated with upstaging of all -stage cutaneous melanomas treated with MMS-I remain undefined. Objective: Determine upstaging frequency and factors associated with tumor upstaging for all -stage melanomas treated with MMS-I. Methods: In this retrospective, single -center case series, all cases of invasive and in situ melanoma treated with MMS-I between 2008 and 2018 were reviewed. Patient and tumor characteristics were recorded and compared between tumors that were and were not upstaged from their initial T stage. Results: Of the 962 melanoma MMS-I cases identified, 44 (4.6%) were upstaged, including 5.6% of in situ and 2.5% of invasive tumors. Risk factors for upstaging included lack of excisional intent at the time of initial biopsy ( P \ .01), nonlentigo maligna subtype ( P = .03), female sex ( P = .02), and initial in situ diagnosis ( P = .03). Nonstatistically significant characteristics evaluated included patient age ( P = .97), initial Breslow depth ( P = .18), and biopsy type ( P = .24). Limitations: Retrospective study design. Conclusions: All -stage cutaneous melanomas treated with MMS-I are associated with low upstaging rates. Tumor upstaging is associated with lack of excisional intent, female sex, and in situ tumors. ( JAAD Int 2024;16:3-8.)