The mutation in Nf1 gene causes cells belonging to the Schwann cell lineage to be susceptible to benign tumor formation [117, 118]; however, to form neurofibromas, the NF1 deficient microenvironment is also necessary [119]. In Dhh-Cre;Nffl/fl and Mpz-Cre;Nf1fl/fl mice with Nf1 gene was removed from the Schwann cell lineage, the development of plexiform neurofibromas, dermal neurofibromas, and pigmentation was observed [120, 121]. This evidence concerns the gene NF1 and benign neoplasm.