Nail unit melanoma treated with Mohs micrographic surgery: Technique, local recurrence rate, and surgical outcomes

Background: Nail unit melanoma (NUM) is increasingly treated with digit-sparing surgery, but few published case series describe Mohs micrographic surgery (MMS) for NUM. Objective: To describe the surgical technique, local recurrence rates, and reconstruction method for a large series of NUM treated with MMS using melanoma antigen recognized by T cells-1 immunostaining. Methods: Biopsy-proven NUM treated with MMS-melanoma antigen recognized by T cells-1 were identified from a prospectively maintained database (2008-2023). Primary outcome was local recurrence rate. Secondary outcomes included rate of subclinical spread and rate of ablative versus reconstructive amputation. Results: Sixty-nine NUM were identified, including 51 melanomas in situ (73.9%) and 18 invasive melanomas (26.1%) with mean Breslow thickness of 1.07 mm (range 0.2-5.4 mm). One local recurrence (1/69, 1.4%) occurred during a mean follow-up time of 38.2 months. Subclinical spread (>1 Mohs stage) was common (38/69, 55.1%). Amputation was rarely necessary to clear the melanoma (5/69, 7.2%), but amputation at different levels was performed to reconstruct 33 cases (33/69, 47.8%) with extensive exposed bone. Limitations: Single center cohort and lack of patient-reported outcomes. Conclusion: MMS treats NUM with low local recurrence rates. Amputation is rarely necessary to obtain clear tumor margins, but it may be necessary or desirable to reconstruct MMS defects with extensive exposed bone.