PTEN and melanoma: The analysis by whole exome sequencing, conducted on melanoma tissues from 28 patients suffering of double-drug disease progression, identified in the majority of cases (about 68%) molecular alterations in the MAPK and PI3K/PTEN/AKT signaling pathways, as previously reported [26], i.e. same genetic alterations, which occur in the resistance to BRAFi monotherapies were evident also in the double-drug disease progression [22].