Malignant Peripheral Nerve Sheath Tumor (MPNST)

What is a malignant peripheral nerve sheath tumor?

A malignant peripheral nerve sheath tumor (MPNST) is a very rare type of soft tissue sarcoma. In MPNST, there are malignant (cancerous) tumors in the sheaths or layers of tissue that protect nerves in your peripheral nervous system. You can have this type of tumor in your arms and legs, but it may also affect your pelvis, abdomen, head and neck. Removing tumors with surgery can cure the condition, but the tumors often come back (recur).

How rare is an MPNST?

It’s very rare. Each year, about 1 in 1 million people learn they have a malignant peripheral nerve sheath tumor. This condition typically affects people aged 30 to 50.

People who have the inherited disorder neurofibromatosis type 1 (NF1) often develop MPNST. Between 25% and 50% of people who have a malignant peripheral nerve sheath tumor also have NF1.

In general, people with NF1 develop MPNST earlier than people who don’t have NF1. And NF1-associated MPNST is somewhat more common in men and people assigned male at birth (AMAB) compared to non-NF1 MPNST.

What are the symptoms of a malignant peripheral nerve sheath tumor?

MPNSTs develop anywhere you have peripheral nerves, but they typically affect places like your arms and legs. They can appear in your pelvis, chest, abdomen or head and neck. MPNST symptoms may include:

• A lump under your skin that keeps growing. These tumors may be as small as a pea (about 2 centimeters) or as large as a grapefruit (about 10 cm).
• Pain (especially if you have NF1).
• Paresthesia (tingling).
• Weakness in your arms and legs.

What causes MPNST?

Studies show neurofibromatosis type 1 accounts for 50% of malignant peripheral nerve sheath tumors. Other causes include:

• Radiation therapy: About 10% of people with MPNST receive radiation therapy for other medical issues.
• Genetic mutations: Researchers have found several different genetic mutations that turn normal nerve sheath cells into abnormal cells that multiply and create tumors.
• Certain neurofibromas: People with plexiform neurofibroma have an increased risk for MPNST.

How is a malignant peripheral nerve sheath tumor diagnosed?

A healthcare provider will perform a physical exam and assess your overall health. This includes a review of your medical history, family history and symptoms. They may do:

• Imaging tests: Providers may do magnetic resonance imaging (MRI) and positron emission tomography (PET) scans.
• Biopsy: Providers may do a biopsy to obtain tissue for a medical pathologist to examine under a microscope.
• Genetic tests: If you have a malignant peripheral nerve sheath tumor, your provider may recommend you and close family members have genetic tests to find out if you or they have neurofibromatosis type 1 (NF1) or neurofibromatosis type 2 (schwannomatosis), another type of nerve sheath tumor.

What are treatments for MPNST?

Healthcare providers typically do surgery to remove a malignant peripheral nerve sheath tumor. In some cases, surgery may not be an option for people who have:

• Large tumors (tumors that are 5 cm or larger.)
• Metastatic tumors.
• Tumors located very close to complex nerve networks that could be damaged during surgery.

Providers may treat MPNST by combining surgery and chemotherapy or radiation therapy. They may do radiation therapy before or after surgery.

Researchers are studying immunotherapy or targeted therapy as potential new or additional treatments. If you have a malignant peripheral nerve sheath tumor, you may want to talk to your provider about participating in a clinical trial that’s testing new treatments.

What are possible treatment complications or side effects?

Surgery may cause the following complications:

• Reaction to general anesthesia.
• Excessive bleeding (hemorrhage).
• Pain.
• Surgical scars.
• Surgical wound infection.

Treatments like chemotherapy or radiation may cause side effects, including:

• Diarrhea.
• Fatigue.
• Nausea and vomiting.

What’s the prognosis for someone with MPNST?

Your prognosis is what your healthcare team believes will happen after you finish treatment. They base MPNST prognoses on several factors:

• NF1 status: The prognosis for people with NF1 who have these tumors is less positive than the prognosis for people who don’t have NF1.
• Tumor grade: Pathologists classify tumors as being high-grade or low-grade, based on how cells appear when viewed under a microscope. High-grade tumors have cancerous cells that divide very quickly and are likely to spread.
• Tumor size: MPNSTs may grow up to 10 centimeters. In general, large tumors are more difficult to remove with surgery.
• Metastasis: Tumors that spread from where they started are more difficult to treat.

As you can see, many things may affect your prognosis, and not every factor listed will apply to you. Ask your healthcare provider to explain your prognosis. They know your situation and are your best resource for information.

MPNST survival rates

Survival rates are estimates based on other people’s experiences with malignant peripheral nerve sheath tumors. These tumors are rare, which makes it difficult for experts to set estimates. According to the National Cancer Institute (U.S.), 23% to 69% of people with MPNST were alive five years after they were diagnosed. That’s a wide range, so it’s a good idea for you to ask your healthcare provider for their thoughts on your situation.

How do I take care of myself?

If you have a malignant peripheral nerve sheath tumor, you’re dealing with a rare cancer that often comes back after treatment. Here are some programs that may be helpful:

• Palliative care: In palliative care, you work with a team of specially trained providers who can help you manage MPNST symptoms and treatment side effects. More than that, they can be emotional support.
• Cancer survivorship: Cancer is a journey. Cancer survivorship programs help you navigate cancer, from diagnosis and treatment to understanding what to do if cancer comes back.