CDKN2B and plexiform neurofibroma: Furthermore, the silencing or homozygous deletion of CDKN2A, ARF, and CDKN2B has been detected in a subset of PNF, atypical neurofibromas, as well as MPNSTs, indicating that these genes have a role not only in the formation of PNFs, but probably also in MPNST development [13,64].