NF1 and neoplasm: Two events seem to be essential for the development of NF1 tumours: the inactivation of the remaining wild type NF1 allele (somatic mutation) in a schwann cell precursor; and a tumour microenvironment produced by the NF1 haploinsufficency in other tumoural elements (fibroblasts, perineural-like fibroblasts and mast cells).