Malignant peripheral nerve sheath tumor of the cauda equina. 
Only one case of malignant peripheral nerve sheath tumor (MPNST) affecting the cauda equina region has been reported earlier.  A 32-year-old male with congenital multiple subcutaneous swellings presented with low back pain, progressive paraparesis and bladder-bowel dysfunction.  Magnetic resonance imaging (MRI) demonstrated a heterogeneously enhancing intradural lesion at L2-L4.  At operation, on opening the dura, multiple nodular, firm matted masses attached to the lumbosacral nerve roots were encountered.  Peripheral lesions were partially excised.  Histopathological exam revealed varied cellularity with necrosis and pleomorphic nuclei suggestive of MPNST.  MRI features, pathophysiological characteristics and the literature are reviewed.