SOS1 and RASopathy: But, whilst mutant NF1 is known to cooperate with RASopathy genes (RASA2, PTPN11, SOS1, RAF1 and SPRED1) in melanoma and although NF1 is found to be frequently mutated (25–30%) in melanomas harbouring wild-type BRAF and NRAS, it is curious that melanoma is not a tumour type associated with NF1 [8, 49–51].