Abstract

While morphology remains the gold standard, ancillary diagnostic molecular techniques can mitigate the challenge of distinguishing benign from malignant melanocytic neoplasms. Currently, the detection of copy number variation (CNV) by FISH and chromosomal microarray (CMA) are the most useful and accepted methods, but remain expensive, consuming of time and resources, inaccessible and somewhat subjective. Alterations of MYC and MYB genes have been implicated in the development of melanoma. We aim to develop a cheaper, faster, more accessible and objective molecular assay to detect MYC and MYB genetic changes with comparable efficacy to FISH and CMA using droplet-digital PCR (ddPCR). DNA was extracted from 42 skin samples from 33 patients diagnosed with benign, borderline, malignant, and metastatic melanocytic neoplasms at our institution from 2013 to 2022. A multiplex ddPCR assay was performed using the Biorad QX200 System, and ddPCR results were compared to CMA data. Histopathologic diagnosis of each case had been determined by a board certified dermatopathologist prior to analysis. Using four reference genes and mean ddPCR values, concordance analysis of ddPCR with CMA for quantification of MYC and MYB CNV revealed a sensitivity and specificity of 88% and 89% for MYC, and 79% and 96% for MYB, respectively. The threshold values were 2.48 for MYC gain and 1.32 for MYB loss. Subsequent threshold validation analysis showed a sensitivity and specificity of 88% and 100% for MYC, and 71% and 100% for MYB, respectively. This proof-of-concept study demonstrates the first use of a rapid, reproducible, reliable and inexpensive method using ddPCR to identify MYC and MYB copy number changes in melanocytic neoplasms. Our ddPCR results were comparable to the reference standard, CMA. We hope this novel molecular technology may be furthered developed to aid in the prognostication and diagnosis of challenging melanocytic lesions and becomes widely available to our patients.

Financial Disclosure:
No current or relevant financial relationships exist.