Identification of recurrent mutational events in anorectal melanoma

Mod Pathol. 2017 Feb;30(2):286-296. doi: 10.1038/modpathol.2016.179. Epub 2016 Oct 14.

Abstract

Anorectal melanoma is a rare disease that carries a poor prognosis. To date, limited genetic analyses confirmed KIT mutations as a recurrent genetic event similar to other mucosal melanomas, occurring in up to 30% of anorectal melanomas. Importantly, a subset of tumors harboring activating KIT mutations have been found to respond to c-Kit inhibitor-based therapy, with improved patient survival at advanced tumor stages. We performed comprehensive targeted exon sequencing analysis of 467 cancer-related genes in a larger series of 15 anorectal melanomas, focusing on potentially actionable variants based on gain- and loss-of-function mutations. We report the identification of oncogenic driver events in the majority (93%) of anorectal melanomas. These included variants in canonical MAPK pathway effectors rarely observed in cutaneous melanomas (including an HRAS mutation, as well as a BRAF mutation resulting in duplication of threonine 599), and recurrent mutations in the tumor suppressor NF1 in 20% of cases, which represented the second-most frequently mutated gene after KIT in our series. Furthermore, we identify SF3B1 mutations as a recurrent genetic event in mucosal melanomas. Our findings provide an insight into the genetic diversity of anorectal melanomas, and suggest significant potential for alternative targeted therapeutics in addition to c-Kit inhibitors for this melanoma subtype.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Anus Neoplasms / genetics*
  • Anus Neoplasms / pathology
  • Exons
  • Female
  • Humans
  • Male
  • Melanoma / genetics*
  • Melanoma / pathology
  • Middle Aged
  • Mutation
  • Neurofibromin 1 / genetics
  • Phosphoproteins / genetics*
  • Proto-Oncogene Proteins B-raf / genetics*
  • RNA Splicing Factors / genetics*
  • Rectal Neoplasms / genetics*
  • Rectal Neoplasms / pathology
  • Signal Transduction / genetics

Substances

  • Neurofibromin 1
  • Phosphoproteins
  • RNA Splicing Factors
  • SF3B1 protein, human
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf