Among primary nerve sheath tumors, schwannomas and neurinomas are the most common. While the schwannomas (neurilemomas) originate in schwann cells, neurofibromas arise from all the constitutive parts of the nerve. The behavior of each tumor is quite different and only neurofibromas may present malignant transformation, especially when arising in patients with Von Recklinghausen disease (NF1 with multiple neurofibromas).