Commentary on Mohs Micrographic Surgery Using MART-1 Immunostaining for Nail Unit Melanoma in Situ.

In the January issue,Matsumoto and colleagues present data from their single institution experience using Mohs micrographic surgery (MMS) for nail unit melanoma in situ. This retrospective series includes 14 patients who were treated over a 10-year time period with an average postprocedure follow-up duration of 6 years. During the follow-up period, which ranged from 5 to 139 months, only one patient (7.1%) developed recurrence. The authors provide detailed explanations of their technique, including how they incorporateMART-1 immunostaining into their process. Our readership will benefit greatly from their experience. There has been growing evidence of treatment success and patient satisfaction after functional surgery over amputation for nail unit melanoma in situ. This manuscript provides further compelling evidence for using functional surgery to treat nail unit melanoma in situ, and in particular supports using MMS with MART-1 immunostaining for this purpose. This manuscript highlights a variety of technical issues related to the success of this procedure. Nail unit anatomy can make removal of the key anatomic areas challenging. Given the small safety margin between the nail matrix epithelium and underlying distal phalanx, there is a risk of damage to the extensor tendon, and the potential to leave behind matrix horn epithelium that could act as a nidus for tumor recurrence and/or spicule formation. Familiarity with these issues will allow for planning to avoid or minimize their impact. The authors note that processing nail unit tissue during MMS can present challenges as well. Specialized training and preparation for histotechnicians is essential in this regard. The benefits of using MART-1 immunostaining to evaluate residual nail unit melanoma in situ or residual atypical melanocytic proliferations are well demonstrated in the manuscript. The nail unit is known to be a challenging area for histopathologic interpretation of melanocytic lesions even with routinely prepared sections. For this reason, immunoperoxidase staining is standard for the analysis of such lesions. Consistent with the techniques outlined in this study, MART-1/Melan-A immunostaining is the preferred method for identification of melanocytes in the nail unit. The authors’ use of MART-1 staining is essential to their technique, which optimizes accurate histopathologic evaluation of the nail unit tissue so as to provide the best possible treatment for each patient. The combination of challenging anatomy and challenging histopathology means that specialized preparation and training is essential for successful treatment of nail unit melanoma in situ with MMS incorporating MART-1 immunostaining. Long-term post-procedure clinical follow-up also remains important for patients treated with this technique, particularly since lesion recurrence in this series occurred years later. Considering the importance of this manuscript, it is a pleasure to present an additional jointly written invited commentary from Drs. Eckart Haneke and Nathaniel Jellinek. Both are internationally recognized nail experts and have particular experience with treatment of nail unit melanoma.