NF1 and malignant peripheral nerve sheath tumor: NF1 microdeletion patients generally display a more severe phenotype than patients with NF1 gene mutation, showing variable facial dysmorphism, developmental delay, cognitive impairment, a high number of early-onset neurofibromas, cardiovascular malformations (Venturin 2004), and an increased risk of malignant peripheral nerve sheath tumors (MPNSTs) (De Raedt et al. 2003; Pasmant et al. 2010; Zhang et al. 2015).