The dynamic molecular landscape of malignant melanomas arising from congenital or common nevi

Background. Some cutaneous melanomas are arising from nevus, that can be either from the congenital or the common type. Objective: We aimed at comparing: i) the genomic landscape of small/medium congenital versus common nevi and ii) explore whether there is a different mutational pattern acquired during progression to melanoma between this two groups. Methods: We analysed BRAF, NRAS and TERT promoter status on micro-dissected melanocytic nevi and performed massively parallel sequencing on paired melanomas in 42 patients, half from the congenital and half from the common type. Results: Both common and small/medium congenital nevi mainly harboured BRAF V600E mutation at a similar rate. During melanoma progression, both groups acquired recurrent second hit TERT promoter mutations. Additional genomic alterations affecting oncogenic pathways also accumulated during progression, without a specific pattern. Conclusions: Small/medium congenital and common nevi shared the same mutational landscape and did not show any difference during progression to melanoma.