The malignant peripheral nerve sheath tumor (MPNST) is the malignant counterpart to benign soft tissue tumors such as neurofibromas and schwannomas. This term is preferred to older designations such as malignant schwannomas and neurofibrosarcomas. It is most common in the deep soft tissue, usually in close proximity of a nerve trunk. The most common sites include the sciatic nerve, brachial plexus, and sarcal plexus. The most common symptom is pain which usually prompts a biopsy. Most cases average more than 5 cm in diameter. On sections, it may have a white surface with areas of necrosis or hemorrhage. It is the most common sarcoma arising in the setting of von Recklinghausen’s disease.
10% of all soft tissue sarcomas seen in consultation with 50% occurring in the setting of neurofibromatosis I.