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Abstract

As the incidence of melanoma on sun damaged skin has been increasing, Mohs micrographic surgery (MMS) has become a frequently utilized treatment method. A recent study published by our group showed a low rate of upstaging during MMS. We hypothesized that this was because a majority of the tumor was removed with initial biopsy. Few studies, however, have characterized how often melanoma is fully removed at the time of diagnostic biopsy, as determined by the absence of residual disease on MMS. This study aims to address this knowledge gap. We hypothesized that many melanomas would be completely removed by initial biopsy, with residual disease present in a minority of cases. We retrospectively reviewed 109 patients who underwent MMS for melanoma between 2019 and 2022 at a single academic center, all with prior diagnostic punch or shave biopsies. Residual melanoma was identified in 64.2% of cases, including 57.8% with melanoma in situ and 6.4% with invasive melanoma. We assessed associations between residual disease and biopsy type, histologic diagnosis (in situ vs. invasive), anatomic site, patient age and sex, biopsy-to-surgery interval, and reported margin status. No variable significantly predicted the presence or type of residual tumor. These findings indicate that residual melanoma is common following biopsy and not reliably predicted by routine clinical or histopathologic factors.