As previously reported7,10,31, we found a substantial proportion of mucosal melanomas had aberrations of the MAPK pathway, including frequent mutations in NRAS, BRAF, NF1, and KIT. Mutations were also identified in several other known cancer driver genes, including CTNNB1, implicating the previously unappreciated role of WNT signaling in the genesis of mucosal melanomas. Here, CTNNB1 is linked to mucositis.