Early studies on small subsets of NF1-associated neurofibrosarcomas identified deletions on chromosome 17 outside of the NF1 locus [63,64], which included the coding region for TP53. Screening for TP53 inactivation in a panel of 20 MPNST identified LOH in over half of the tumors tested [55]. This evidence concerns the gene NF1 and malignant peripheral nerve sheath tumor.