Malignant peripheral nerve sheath tumors are a rare type of cancer that occurs in the lining of the nerves that extend from the spinal cord into the body. Malignant peripheral nerve sheath tumors used to be called neurofibrosarcomas.

Malignant peripheral nerve sheath tumors can occur anywhere in the body, but most often occur in the deep tissue of the arms, legs and trunk. They tend to cause pain and weakness in the affected area and may also cause a growing lump or mass.

Malignant peripheral nerve sheath tumors are typically treated with surgery. In certain cases, radiation therapy and chemotherapy also may be recommended.


Signs and symptoms of malignant peripheral nerve sheath tumors include:

  • Pain in the affected area
  • Weakness when trying to move the affected body part
  • A growing lump of tissue under the skin

When to see a doctor

Make an appointment with your doctor if you have any persistent signs and symptoms that worry you. Malignant peripheral nerve sheath tumors are rare, so your doctor may investigate more-common causes for your symptoms.

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It's not clear what causes most malignant peripheral nerve sheath tumors.

Doctors know that these cancers begin when a cell in the protective lining around a nerve develops an error (mutation) in its DNA. The mutation tells the cell to multiply rapidly and to continue living when other cells would normally die. The accumulating cells form a tumor that can grow to invade nearby tissue or spread to other areas of the body.

Risk factors

Factors that increase the risk of malignant peripheral nerve sheath tumors include:

  • Previous radiation therapy for cancer. A malignant peripheral nerve sheath tumor may develop in the area treated with radiation 10 to 20 years after treatment.
  • Noncancerous nerve tumors. Malignant peripheral nerve sheath tumors can develop from noncancerous (benign) nerve tumors, such as neurofibroma.
  • An inherited condition that increases risk of nerve tumors. Malignant peripheral nerve sheath tumors occur more frequently in people with neurofibromatosis 1.

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  1. Gilchrist JM, et al. Peripheral nerve tumors. https://www.uptodate.com/contents/search. Accessed July 20, 2017.
  2. Winn HR, ed. Benign and malignant tumors of the peripheral nerve. In: Youmans Neurological Surgery. 7th ed. Philadelphia, Pa.: Elsevier; 2017. https://www.clinicalkey.com. Accessed July 20, 2017.
  3. Stucky CH, et al. Malignant peripheral nerve sheath tumors (MPNST): The Mayo Clinic experience. Annals of Surgical Oncology. 2012;19:878.
  4. Warner KJ. Allscripts EPSi. Mayo Clinic, Rochester, Minn. April 4, 2017.


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