Mondo Description An intraneural or extraneural neoplasm arising from nerve tissues and neural sheaths. It is composed of perineurial-like fibroblasts and Schwann cells. It usually presents as a localized cutaneous lesion and less often as a circumscribed peripheral nerve mass. Patients with neurofibromatosis type 1 present with multiple masses. Neurofibromas which arise from major nerves and plexiform neurofibromas are precursor lesions to malignant peripheral nerve sheath tumors.