Abstract

The diagnosis of nail unit melanoma (NUM) is challenging for dermatologists and dermatopathologists. Diagnosis and treatment of NUM is often delayed due to patient reluctance to undergo a potentially painful nail unit surgical procedure and the challenge of adding such procedures to a busy clinic, resulting in worse patient outcomes. Melanocytes and/or melanocyte remnants (MR) within nail clippings and the nail plate have been identified as a diagnostic sign associated with NUM in adults. Herein we present a representative case illustrating the utility of this diagnostic maneuver and the benefit for patient care. A 58-year-old white female presented to our practice with a 12-month history of right thumbnail unit longitudinal melanonychia with multiple pigmented bands and a combined distal width of 4 mm. She was reluctant to undergo a nail matrix biopsy but did allow a nail clipping for evaluation. Histopathologic examination of the nail plate revealed areas of pigmentation with multiple MR in various layers. Staining for S100, MART 1, and PRAME were negative. The presence of MR were highly suggestive of NUM. Because of these findings an urgent nail unit biopsy was performed and demonstrated NUM in situ. Routine nail clipping is a basic procedure with which every clinician and patient is familiar. Recent accumulation of the literature shows the relationship between MR in the nail plate and nail clippings with NUM. The nail clipping can be used as a triage mechanism, separating out patients who require urgent nail unit biopsies from those that need routine biopsies or other evaluations. The dermatopathologist can thus play a crucial role in the use of a nail clipping as a life-saving diagnostic maneuver. Our patient adds to the growing literature highlighting MR as a high-risk feature of NUM and we feel there is sufficient evidence at this point to call on dermatologists and dermatopathologists to modernize the evaluation of melanonychia with this innovation.

Financial Disclosure:
No current or relevant financial relationships exist.