260 Mosaic BRAF fusions are a recurrent cause of multiple congenital melanocytic naevi

Abstract

Congenital melanocytic naevi (CMN) are moles present at birth, and when multiple or very extensive can involve other organ systems as well as predisposing to melanoma. Some CMN develop a highly proliferative phenotype whose progression is poorly understood. Genotypically, CMN are caused by mosaic NRAS missense mutations in 67% of cases and BRAF missense mutations in 7% of cases. Single cases of mosaic gene fusions have been previously described. To investigate the remaining 25%, skin biopsies from 19 patients shown to be double wildtype for NRAS/BRAF underwent transcriptome-wide paired-end RNA sequencing to detect gene fusion transcripts.