The Genetic Evolution of Melanoma from Precursor Lesions

TLDR: The succession of genetic alterations during melanoma progression was defined, showing distinct evolutionary trajectories for different melanoma subtypes, and an intermediate category of melanocytic neoplasia was identified, characterized by the presence of more than one pathogenic genetic alteration and distinctive histopathological features.

Abstract: BackgroundThe pathogenic mutations in melanoma have been largely catalogued; however, the order of their occurrence is not known. MethodsWe sequenced 293 cancer-relevant genes in 150 areas of 37 primary melanomas and their adjacent precursor lesions. The histopathological spectrum of these areas included unequivocally benign lesions, intermediate lesions, and intraepidermal or invasive melanomas. ResultsPrecursor lesions were initiated by mutations of genes that are known to activate the mitogen-activated protein kinase pathway. Unequivocally benign lesions harbored BRAF V600E mutations exclusively, whereas those categorized as intermediate were enriched for NRAS mutations and additional driver mutations. A total of 77% of areas of intermediate lesions and melanomas in situ harbored TERT promoter mutations, a finding that indicates that these mutations are selected at an unexpectedly early stage of the neoplastic progression. Biallelic inactivation of CDKN2A emerged exclusively in invasive melanomas. PTEN...