Thirty patients (26%) developed MPNST in the context of NF-1, and 83 patients (74%) developed MPNST spontaneously.Evaluation of age of MPNST diagnosis by gender revealed a trend toward males developing MPNST at an earlier age than females (Figure 2; median age 35 years versus 39.5 years, p = 0.048). This evidence concerns the gene NF1 and malignant peripheral nerve sheath tumor.