- Discussion:
    - also called malignant schwannoma or fibrosarcoma of nerve sheath;
    - extracompartmental high grade tumor that develops from sheaths (Schwann cells) of  peripheral nerves;
    - usually is a primary lesion occuring along proximal major nerve trunks,
    - tumor is usually asymptomatic until it causes neuropraxia;
    - gross inspection reveals a large fusiform mass;
    - rather than being displaced by tumor, associated nerve enters proximal pole of the tumor and exits the distal pole;
    - associated conditions:
         - neurofibromatosis:
               - neurosarcoma occassionally develops as secondary transformation of neurofibromatosis;
               - hence, look for the physical exam and radiographic characteristics of this disorder;
               - prognosis for patients with primary neurosarcoma is more favorable than for those with malignant transformation of neurofibromatosis;
               - often the transition to malignancy is heralded by new onset neurologic deficit;

- Histology:
    - fibrillar pattern is loose & have with increased cellularity;
    - multiple mitotic figures, & wavy eosinophilic pattern of neural tissue with comma shaped nuclei;
    - in an undifferentiated lesion, electron microscopic examination is needed to distinguish it from fibrosarcoma.

- Treatment:
    - wide excision w/ wide margin, if possible;
    - otherwise radical ampuatation is considered