NF1 and plexiform neurofibroma: Neurofibromas are complex tumors originating from the peripheral nerve sheath, composed of Schwann cells (SCs) undergoing loss of heterozygosity (LOH) at the NF1 locus in an NF1+/− milieu composed by many other NF1 haploinsufficient (HI) cells, including mast cells, macrophages and myofibroblasts [1].