CDKN2A and plexiform neurofibroma: A deletion at 9p21.3, which includes genes CDKN2A/2B, was identified in 15/16 (94%) ANF and in 16/23 (70%) high-grade MPNST but not in plexiform neurofibromas; supporting the hypothesis that ANF are premalignant tumors, with the CDKN2A/B deletion as the first step in the progression toward MPNST [69].