Malignant Peripheral Nerve Sheath Tumor
A rare, aggressive cancer of the nerve lining
Quick Facts
- Type: Soft tissue sarcoma (nerve sheath cancer)
- Strong link: Neurofibromatosis type 1 (NF1)
- Common sites: Arms, legs, trunk, deep nerves
- Key warning: A growing, painful lump or new nerve symptoms
Overview
A malignant peripheral nerve sheath tumor (MPNST) is a rare and aggressive cancer that develops in the cells forming the protective sheath around peripheral nerves, the nerves running outside the brain and spinal cord. It is a type of soft tissue sarcoma.
MPNSTs can arise on their own, after previous radiation therapy, or from a pre-existing benign nerve tumor (a neurofibroma) in people with neurofibromatosis type 1 (NF1). They most often occur in the arms, legs, and trunk. Because these tumors can grow and spread, prompt diagnosis and treatment at a specialized center are important. People with NF1 should be alert to any nerve tumor that changes or becomes painful.
Symptoms
Symptoms come from the growing tumor and its effect on the nerve it involves.
- A lump or mass, often deep in a limb or the trunk, that is enlarging
- Pain in or around the lump
- Numbness, tingling, or weakness in the area the nerve supplies
- In people with NF1: an existing nerve lump that suddenly grows, becomes painful, or feels firmer
A nerve tumor that grows quickly, becomes painful, or causes new or worsening weakness or numbness, especially in someone with neurofibromatosis, should be evaluated without delay.
Causes
MPNSTs develop when cells of the nerve sheath acquire changes that make them cancerous. Recognized routes include:
- Neurofibromatosis type 1: A significant proportion of MPNSTs occur in people with NF1, often arising from a pre-existing neurofibroma.
- Previous radiation therapy: MPNSTs can develop years after radiation to an area.
- Sporadic cases: Many occur in people without NF1 or prior radiation, for reasons that are not well understood.
MPNSTs are not contagious.
Risk Factors
- Neurofibromatosis type 1 (the major risk factor)
- Previous radiation therapy
- A history of multiple or large plexiform neurofibromas in NF1
- Young to middle adulthood, though MPNSTs can occur at various ages
Diagnosis
Diagnosis requires imaging and tissue analysis.
- MRI scan: The main imaging test to assess the tumor's size, location, and relationship to nerves.
- PET scan: Sometimes used to help identify a tumor that may be turning cancerous and to check for spread.
- Biopsy: A tissue sample is examined to confirm the diagnosis and determine the tumor grade.
- Staging tests: Imaging such as a CT scan of the chest to check whether the cancer has spread, as MPNSTs can spread to the lungs.
Treatment
Treatment is best delivered by a specialized sarcoma team and depends on the tumor's size, location, grade, and whether it has spread.
- Surgery: The main treatment, aiming to remove the tumor completely with a margin of healthy tissue.
- Radiation therapy: Often used before or after surgery to reduce the chance of the tumor returning.
- Chemotherapy: May be considered, particularly for larger, high-grade, or spread tumors, though its role is individualized.
- Rehabilitation: Physical therapy and support to recover function after treatment.
Because MPNSTs can be aggressive, close follow-up after treatment is important to watch for any recurrence or spread.
Prevention
MPNSTs cannot be reliably prevented, but early detection improves outcomes:
- People with neurofibromatosis type 1 should have regular specialist follow-up and report any nerve lump that grows, becomes painful, or causes new symptoms
- Avoiding unnecessary radiation exposure
- Prompt evaluation of any enlarging deep lump
When to See a Doctor
See a doctor promptly for a deep lump that is growing, a nerve lump that becomes painful, or new numbness or weakness, particularly if you have neurofibromatosis type 1. Seek urgent evaluation for:
- A rapidly enlarging or increasingly painful mass
- Fast-worsening weakness or loss of sensation
- An existing nerve tumor that suddenly changes in size, firmness, or pain
Frequently Asked Questions
What is a malignant peripheral nerve sheath tumor?
It is a rare, aggressive cancer that develops in the cells lining peripheral nerves, classed as a soft tissue sarcoma. It can arise on its own, after radiation, or from a benign nerve tumor in people with neurofibromatosis type 1.
Who is most at risk of MPNST?
People with neurofibromatosis type 1 have a significantly increased risk, often with the tumor arising from a pre-existing neurofibroma. Previous radiation therapy is another recognized risk factor.
What warning signs should people with NF1 watch for?
An existing nerve lump that suddenly grows, becomes painful, feels firmer, or causes new numbness or weakness should be evaluated promptly, as these can signal a benign tumor turning cancerous.
How is MPNST treated?
Surgery to remove the tumor completely is the main treatment, often combined with radiation therapy. Chemotherapy may be used for larger, high-grade, or spread tumors. Care is best provided by a specialized sarcoma team.
Can MPNST spread?
Yes. MPNSTs can spread, most often to the lungs, which is why staging tests and close follow-up after treatment are important. Early detection and complete surgical removal improve the chance of a good outcome.
References
- National Cancer Institute (NCI). Soft Tissue Sarcoma Treatment.
- Children's Tumor Foundation. Malignant Peripheral Nerve Sheath Tumors.
- MedlinePlus, U.S. National Library of Medicine. Soft tissue sarcoma.
- American Cancer Society. Soft Tissue Sarcoma.