Being inhibitors to the BRAF kinase also means they have a common feature biologically related to the paradoxical activation of the MAP kinase pathway associated with upstream activation of pre-existing RAS mutations in a specific type of cell: keratinocytes; in fact, a frequent adverse event related to the use of BRAF inhibitors is the development of secondary cutaneous squamous cell carcinomas and keratoacanthomas [105,116,117]. This evidence concerns the gene BRAF and keratoacanthoma.