Multiple neurofibromas can be associated with neurofibromatosis type I (NF-1) and, a small rate of patients can develop malignant peripheral nerve sheath tumors (MPNST) with dismal clinical outcome; the cumulative lifetime risk of developing MPNST in patients with NF1 is about 8–13% (110). The gene discussed is NF1; the disease is malignant peripheral nerve sheath tumor.