Non-Invasive Genomic Profiling in Pediatric Patients

Background:Pigmented lesions with clinical features suspicious for melanoma are not uncommon in pediatric patients. Evaluation of these lesions is complicated by the low prevalence of pediatric melanoma and challenges associated with performing biopsies in children. The DermTech Melanoma Test (‘the test’) is a non-invasive genomic test designed to rule out melanoma. It consists of the Pigmented Lesion Assay (PLA), which detects RNA gene expression of long intergenic non-coding RNA 00518 (LINC00518, or LINC) and preferentially expressed antigen in melanoma (PRAME), and an add-on assay for DNA promoter mutations in telomerase reverse transcriptase (TERT), which is performed if ordered and if sufficient genomic material is available. Patients younger than 18 years were not included in initial validation studies. In this analysis, we sought to compare genomic biomarker results between uncertain pigmented lesions from adult and pediatric patients. Methods:De-identified samples submitted to the clinical lab for the test from May through October 2022 were used for this analysis. Genomic results were available for 36,377 samples. The anatomic locations of the lesions were categorized as head/neck, trunk, or extremities and compared between adult and pediatric patients. Positivity rates for the PLA (and each individual marker) and the TERT add-on assay were calculated for adults and patients younger than 18 years of age. Results:The PLA was performed on 34,050 skin samples from adults and 2,327 samples from pediatric patients. There were no differences between adults and pediatric patients in anatomic location of the lesions tested. The proportion of PLA-positive samples was similar between adult (7.0%, n=2,393) and pediatric (8.0%, n=187) patients. Rates of biomarkers detected among PLA-positive adult and pediatric patient samples, respectively, were as follows: LINC only (31.4% vs 69.5%), PRAME only (45.5% vs 14.4%), LINC and PRAME (23.0% vs 16.0%). The TERT add-on assay was performed in 11,084 samples from adults and 613 samples from pediatric patients. Of these, TERT was positive in 830 (7.5%) adult and 3 (0.5%) pediatric patient samples. Conclusions:This analysis provides new information about genomic profiling of uncertain pigmented lesions from pediatric patients. While overall PLA positivity rates were similar across adult and pediatric samples, the proportion positive only for LINC was more than two times higher in pediatric samples. Additionally, TERT promoter mutations were rarely detected in pediatric samples. Further investigation of the significance of LINC, PRAME, and TERT abnormalities in lesions from pediatric patients is ongoing.