By contrast, however, Brosseau et al. demonstrated that the Nf1+/– microenvironment can impair malignant progression.107 This result is consistent with the long-standing and puzzling clinical observation of the low malignant potential of the characteristic benign lesions of NF1 patients (e.g. iris hamartomas, café-au-lait macules, cNF). This evidence concerns the gene NF1 and neurofibromatosis type 1.