The genetic evolution of melanoma

Melanoma tumors are driven by a hyperactivated mitogen-activated protein kinase (MAPK) signalling pathway, and therefore can generally be classified by mutations within the B-Raf proto-oncogene (BRAF), RAS family of proto-oncogenes, neurofibromin 1 (NF1), or other genes. At the transcriptional level, several genetic classifications of melanoma have converged on the distinction between melanogenesis (previously microphthalmia) associated transcription factor (MITF)-low and MITF-high phenotypes and expression of immune-related genes. Mutation-based melanoma subtypes are not prognostic, nor are they associated to transcriptomic subtypes, which are in turn prognostic. Intratumoral heterogeneity of melanoma cells adds another layer of complexity, with recent findings of mutational and transcriptional heterogeneity within melanoma tumors. Furthermore, multiple genetic changes have been associated with different stages of melanoma progression. Mutational signatures may also be differentiated at early and late stages of melanoma progression.