Clinical and Histopathological Investigation of Pediatric Melanonychia

Abstract

Hypothesis The natural history of pediatric melanonychia and the necessity of biopsy for ruling out melanoma are debated in the literature. We hypothesize that there is a low rate of malignant nail pathology among pediatric patients undergoing nail bed biopsy for melanonychia. Methods We performed a retrospective chart review of 54 pediatric patients (age <18 years) at a single institution who presented with melanonychia and underwent nail bed biopsy from 2007 to 2022. Data points collected included patient demographics, medical history, physical exam findings, pathology reports, and clinical photos. Univariate and multivariate analyses were performed to assess for risk factors associated with high-risk pathology findings. Results The average age of melanonychia onset was 5.5 years (SD 4.4). The average age of first biopsy was 7.8 years (SD 4.3). On physical exam, 27 patients had at least four features concerning for melanoma (asymmetry, border irregularity, color heterogeneity, diameter > 1/3 of nail, evolving color, evolving diameter, Hutchinson's sign). The most common pathology diagnoses were melanocytic nevus (35%), atypical intraepidermal melanocytic proliferation (AIMP) with benign features (24%), subungual lentigo (22%), and AIMP with concerning features (17%). There were no cases of melanoma in situ or invasive malignant melanoma. On multivariate regression, the only significant risk factor associated with more concerning pathology (AIMP with concerning features) was the calendar year in which biopsy was performed (coefficient = −0.34, P = 0.016). There was no association between physical exam features and high-risk pathology. Twelve patients had surgical re-excision of the lesion, 6 of which were due to incomplete excision of AIMP with concerning features and 6 of which were due to recurrence. Conclusions Our case series did not find any cases of melanoma in situ or malignant melanoma arising from pediatric melanonychia. Atypical intraepidermal melanocytic proliferation with concerning features was associated only with the year in which the biopsy was performed, which may reflect the improved understanding of pediatric melanonychia as often benign despite concerning features on pathology. The decision to perform a nail matrix biopsy in pediatric melanonychia should be based on a collaborative discussion between the patient's parents, dermatologist, and plastic surgeon.