Risk factors associated with tumor upstaging in melanomas treated with Mohs micrographic surgery with melanocytic immunohistochemistry: a retrospective case series

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<0.01), non-lentigo maligna subtype (p=0.03), female sex (p=0.02), and initial in situ diagnosis (p=0.03). Non-statistically significant characteristics evaluated included patient age (p=0.97), initial Breslow depth (p=0.18), and biopsy type (p=0.24). 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.