Abstract

Melanoma of the nail apparatus is deadly and is challenging to diagnose for both dermatologists and dermatopathologists. Misdiagnosis or delayed diagnosis of nail unit melanoma can have fatal consequences and legal ramifications. This presentation educates dermatopathologists on challenges and traps they should be aware of to avoid misdiagnosis of nail unit melanoma. We present a case of a 78-year-old male who presented with pigmentation of the proximal and lateral nail fold of the right 3rd finger with associated nail dystrophy. Biopsy demonstrated an atypical proliferation of melanocytes with increased density and crowding. With the aid of clinical photos, a diagnosis of at least melanoma in-situ was favored. The patient was subsequently treated with Mohs surgery which demonstrated an invasive melanoma, Breslow depth of 0.3 mm. Notably, atypical melanocytes were found within the nail plate that were minimally highlighted with melanocytic markers. This difficult case introduces several themes regarding challenges in the diagnosis of nail unit melanoma: specimens with subtle histopathologic findings, challenges in immunoperoxidase interpretation, and how clinical knowledge and surgical procedural knowledge are mandatory to make the diagnosis. After this presentation, dermatopathologists will be educated on complex scenarios in the diagnosis of nail unit melanoma. Dermatopathologists will be aware of when and how to suspect nail unit melanoma in unusual circumstances and to provide the top level of care for their patients.

Financial Disclosure: No current or relevant financial relationships exist.