Definition of Malignant peripheral nerve sheath tumors
Your peripheral nervous system includes nerves that travel out from your brain and spinal cord (your central nervous system) to other parts of your body. The nerve sheath is the soft tissue that covers the nerve. A malignant peripheral nerve sheath tumor (MPNST) is cancerous — a soft tissue sarcoma that forms from peripheral nerve sheath cells or from noncancerous (benign) peripheral nerve sheath tumors called neurofibromas.
MPNSTs occur most commonly in deep soft tissue along the nerves that run from the buttocks to legs (sciatic nerves), neck to arms or within the pelvis, but they can occur elsewhere. They can be fast growing, with few or no symptoms in the earliest stages, and cause pain or nerve loss as the tumors grow. A small percentage of people who have neurofibromatosis, an inherited condition that causes neurofibromas, develop MPNSTs.