NF1 and neoplasm: In NF1, Yang et al33 demonstrated in experimental models that the pathogenesis of cutaneous and plexiform neurofibromas involved not only the loss of heterozygosity of the NF1 gene (Nf1 −/−) in Schwann cells, but was also necessarily associated to a microenvironment composed of haploinsufficient cells (Nf1 +/−), especially mast cells, which could be more sensitive to the mediators secreted by tumor cells.