Metastatic malignant peripheral nerve sheath tumor of the cauda equina

Malignant peripheral nerve sheath tumor (MPNST) of the cauda equina is rare, with only four reported patients in the literature. We present a 70-year-old woman with a history of left sciatic nerve MPNST that had been treated by left hemipelvectomy 4 years prior. She then presented with disabling right leg weakness that progressed over 7 months. Spine imaging revealed an intradural extramedullary lesion from L5 to S1 with compression of the cauda equina. She underwent an L3-S1 laminectomy with subtotal resection of the lesion, which was diagnosed as a metastatic MPNST. At the 3-month postoperative visit, her lower extremity strength had returned to baseline. The only notable postoperative complication was a superficial wound infection that resolved with antibiotic treatment and wet-to-dry dressing changes. Thus, although uncommon, the spinal canal and cauda equina should be considered as possible locations for metastatic MPNST in the appropriate clinical scenario. To our knowledge, this is the first report of a patient with a metastatic MPNST to the cauda equina.