Background:Staged excision has emerged as a superior treatment option for lentigo maligna (LM) of the head and neck when compared with conventional wide local excision. Assessing surgical excision margins for remaining LM poses a diagnostic challenge.Objectives:To determine whether immunohistochemical (IHC) staining with SOX10 and preferentially expressed antigen in melanoma (PRAME) aids in diagnosing LM on excision margins compared with conventional hematoxylin and eosin and Melan A IHC staining.Methods:This study included cases of LM of the head and neck treated with staged excision. Histological findings were reviewed according to standard criteria for the diagnosis of LM and compared with the results after IHC staining for Melan A, SOX10, and PRAME.Results:The cohort consisted of 35 sections. Based on hematoxylin and eosin and Melan A IHC staining, 23 sections were diagnosed as LM by the initial pathologist. Further staining with SOX10 IHC showed only 8 to be consistent with a diagnosis of LM and 9 revealing features of actinic melanocyte hyperplasia. PRAME was positive in 5 of the 8 cases of LM and negative in all 9 cases of actinic melanocyte hyperplasia (P = 0.009). The presence of melanocyte nests (P = 0.29) and pagetoid spread (P = 0.003) was the most reliable histological findings distinguishing LM from its mimics.Conclusion:SOX10 is a more specific and sensitive marker for melanocytes when assessing for LM on excision margins compared with Melan A. The addition of PRAME can be useful to confirm or exclude the diagnosis in challenging cases.

BACKGROUND The American Society for Dermatologic Surgery (ASDS) International Traveling Mentorship Program (ITMP) has initiated an International Mohs Fellowship Recognition Program, with 3 centers accredited to date. OBJECTIVE To describe and compare the outcomes of Mohs micrographic surgery (MMS) at the three units. METHODS From patient files, we extracted demographic information, as well as tumor type, location of tumor, tumor histology, stages of MMS, and outcomes. RESULTS At the 3 units, 3,899 patients were treated with MMS over a 5-year period in the South African unit, and 1,141 cases in the Romanian unit. Over a 3-year period, 849 cases were treated in the Netherlands unit. Basal cell carcinomas (BCCs) constituted 78.9% (South African unit), 79% (Romanian unit), and 97.2% (Netherlands unit), and squamous cell carcinomas (SCCs) 17.7% (South African unit), 19% (Romanian unit), and 0.7% (Netherlands unit) of the tumors treated. The recurrence rate following MMS was low, at 0.1% (South African Unit) and 0.17% (Romanian Unit) of cases at the end of the study period, with a median follow-up time of 2 years. CONCLUSION Mohs micrographic surgery is an effective treatment modality for removing BCC and SCC at ASDS ITMP–recognized International Mohs Fellowship units.

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