NF1 and neurofibroma: The major limitation of the NPCis model may have to do with the fact that these tumors do not develop through a process that involves progression from benign neurofibroma (with loss of Nf1 only), to pre-malignant atypical neurofibroma (with loss of Nf1 and Cdkn2a), to MPNST with loss of Suz12 or Eed. However, heterozygous germline loss of function mutations in Nf1 and Suz12 have been combined in Cis on chromosome 11 and this resulted in the acceleration of neurofibroma and MPNST-like tumors [25].