Track

Clinical Studies

Abstract

Pigmented nail lesions can present a histological and clinical challenge. Distinguishing melanoma from benign melanocytic lesions in the nail unit relies on correlating the clinical presentation with increases in melanocytic density, nuclear atypia, and confluence. Benign lesions of the pediatric nail unit display dense pagetoid spread of suprabasilar melanocytes with enlarged nuclei and thick dendrites, rendering pediatric melanocytic nail lesions an even greater diagnostic challenge. Recent studies report PRAME as a sensitive and specific marker for acral melanoma and melanoma of the nail unit in adults. PRAME is absent in normal skin epithelium. However, a recent case series demonstrated new and additional findings of some degree of PRAME expression in 31% of adult benign melanocytic lesions of the nail unit. Nail melanoma is a rare diagnosis within the pediatric population but distinguishing the atypical lesions remains challenging. The significance of positive PRAME expression has not been well established in pediatric melanocytic lesions. This study is the first to assess PRAME expression in pediatric melanonychia. We reviewed four cases of pediatric melanonychia biopsies with a pathologic diagnosis of melanocytic nevus, atypical intraepidermal melanocytic proliferation and subungual lentigo. Our findings suggest the PRAME expression was irrelevant to the diagnosis and focal PRAME positivity can be found within the normal pediatric nail unit. In our case series, focal PRAME expression has not shown to be reliable marker for the pediatric pigmented nail lesions. Positive PRAME expression should be interpreted cautiously in this setting until more studies have been conducted.