Malignant peripheral nerve sheath tumors are rare cancers that start in the lining of the nerves. These cancers happen in the nerves that run from the spinal cord into the body, called peripheral nerves. Malignant peripheral nerve sheath tumors used to be called neurofibrosarcomas.

Malignant peripheral nerve sheath tumors can happen anywhere in the body. They mostly occur in the deep tissue of the arms, legs and trunk. They tend to cause pain and weakness where they occur. They might also cause a growing lump or mass.

Surgery is the usual treatment for malignant peripheral nerve sheath tumors. Sometimes, treatment might include radiation therapy and chemotherapy.

Malignant peripheral nerve sheath tumors often cause symptoms that get worse quickly. Symptoms include:

• Pain where the tumor is growing.
• Weakness when trying to move the body part that has the tumor.
• A growing lump of tissue under the skin.

When to see a doctor

Make an appointment with your health care provider if you have ongoing symptoms that worry you. Malignant peripheral nerve sheath tumors are rare, so your provider might first look for more-common causes for your symptoms.

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

Experts know that these cancers begin when a cell in the lining around a nerve gets changes in its DNA. A cell's DNA holds the instructions that tell a cell what to do. The changes tell the cells to make more cells quickly. These cells continue to live when healthy cells die as part of their life cycle.

The cells then can form a mass called a tumor. The tumor can grow into and kill healthy body tissue. In time, the cells can spread to other parts of the body.

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

• Radiation therapy for cancer. A malignant peripheral nerve sheath tumor might occur in the area treated with radiation 10 to 20 years after treatment.
• Noncancerous nerve tumors. Malignant peripheral nerve sheath tumors can develop from nerve tumors that aren't cancerous, such as neurofibroma.
• A condition that runs in families. Malignant peripheral nerve sheath tumors occur more often in people with neurofibromatosis 1. This condition increases the risk of tumors in the nerves.

Tests and procedures used to diagnose malignant peripheral nerve sheath tumors include:

• Neurological exam. A detailed exam of the nervous system, known as a neurological exam, helps a health care provider gather clues for diagnosis.
• Imaging tests. Imaging tests make pictures of the body. The pictures might help providers see the size of the cancer and whether it has spread to other parts of the body. Tests might include magnetic resonance imaging, also called MRI, or magnetic resonance neurography. Other tests might include computed tomography, also called CT scan, and positron emission tomography, also called PET scan.

• Removing a sample of tissue for testing. A biopsy is a procedure to remove a sample of tissue for testing in a lab. The tissue might be removed using a needle that is put through the skin and into the cancer. Sometimes surgery is needed to get the tissue sample.

  The sample is tested in a lab to see if it is cancer. Other special tests give more details about the cancer cells. The health care team uses this information to make a treatment plan.

Treatment for malignant peripheral nerve sheath tumors often involves:

• Surgery. The goal of surgery is to remove the tumor and some of the healthy tissue around it. When that can't be done, surgeons remove as much of the tumor as they can.

  Depending on where a malignant peripheral nerve sheath tumor is and how big it is, surgery can cause nerve damage. In the case of tumors that occur in the arms and legs, surgically removing the arm or leg might be necessary.

  Sometimes, radiation before surgery might shrink a tumor. That might make it more likely that all of the tumor is removed during surgery.

• Radiation therapy. Radiation therapy uses powerful energy beams to kill cancer cells. The energy can come from X-rays, protons or other sources. During radiation therapy, you lie on a table while a machine moves around you. The machine directs radiation to precise points on your body.

  Radiation may be used before surgery to shrink a tumor. This might make it more likely that all of the tumor is removed during surgery. After surgery, radiation therapy can be used to kill any cancer cells that might remain.

• Chemotherapy. Chemotherapy uses strong medicines to kill cancer cells. Chemotherapy might be an option when a malignant peripheral nerve sheath tumor has spread to other parts of the body. Chemotherapy might help control symptoms and slow the growth of the cancer.
• Rehabilitation. After surgery, physical therapists and occupational therapists can help you regain function and movement lost due to nerve damage or from removing an arm or leg.

If you have symptoms that worry you, make an appointment with your doctor.

If you're diagnosed with a malignant peripheral nerve sheath tumor, you'll likely be referred to a doctor who specializes in:

• Conditions that affect the nervous system, known as a neurologist.
• Treating cancer, known as an oncologist.
• Surgery involving bones, known as an orthopedist.
• Surgery involving nerves, known as a neurosurgeon.

Because appointments can be brief and because there's a lot to discuss, it's a good idea to be prepared. Here's some information to help you get ready and know what to expect.

What you can do

Ask a family member or friend to go with you. Sometimes it can be hard to remember all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.

Make a list of:

• Your symptoms, and when they began.
• All medicines, vitamins and other supplements you take, including doses.
• Questions to ask your health care provider.

Some questions to ask at your first appointment include:

• What may be causing my symptoms or condition?
• Are there other possible causes?
• What tests do I need?
• What's the next step in finding my diagnosis and deciding on treatment?
• Are there restrictions that I need to follow in the meantime?

Questions to ask of a specialist:

• Do I have a malignant peripheral nerve sheath tumor?
• What are the goals of treatment for me?
• What treatment do you suggest?
• Do I need to begin treatment right away?
• I have these other health problems. How can I best manage them together?
• What are the possible side effects of treatment?
• If the treatment doesn't work, what's next?
• What is the outlook for my condition?

Be sure to ask other questions you have.

What to expect from your doctor

Your health care provider is likely to ask you questions, including:

• Have your symptoms changed over time?
• Does anything make your symptoms better?
• Does anything make them worse?
• Have you been told you have other medical conditions?