Malignant peripheral nerve sheath tumors (MPNSTs)

Malignant peripheral nerve sheath tumors (MPNSTs) are rare cancers that start as a growth of cells in the covering on nerves. These cancers affect the nerves that run from the spinal cord into the body, called peripheral nerves.

Malignant peripheral nerve sheath tumors can happen anywhere in the body. They mostly occur in the deep tissue of the arms, legs and trunk.

Malignant peripheral nerve sheath tumors are called malignant because they are cancerous. But not all growths that happen in nerve coverings are cancers. Some nerve sheath tumors are noncancerous, also called benign. Both benign and malignant tumors cause a growth of cells. Malignant tumors tend to grow quickly, while benign tumors usually grow slowly. The malignant cells can spread to other parts of the body. Benign cells don't spread.

Surgery is the main treatment for malignant peripheral nerve sheath tumors. When the cancer can be removed completely, this gives the greatest chance for a cure. Still, MPNSTs often come back after surgery or spread despite treatment. Sometimes the cancer happens in a place where it's hard to remove completely. When the cancer spreads or can't be removed completely, treatments can help slow the growth and help with symptoms, such as pain.

Malignant peripheral nerve sheath tumors are a type of soft tissue sarcoma. Soft tissue sarcomas are cancers that happen in the tissues that connect, support and surround other body structures. In the past, MPNST was known as neurofibrosarcoma. Another older term for this condition is malignant schwannoma, which refers to the fact that MPNST often involves nerve sheath cells called Schwann cells.

Malignant peripheral nerve sheath tumors (MPNSTs) may cause signs and symptoms that get worse quickly. Symptoms include:

• A new, growing lump of tissue under the skin.
• Fast growth in a benign nerve tumor that wasn't growing or was growing slowly.
• Changes in sensation, such as a burning or tingling feeling in the area of the tumor.
• Pain where the tumor is growing.
• Weakness when trying to move the body part that has the tumor or when trying to move muscles that are controlled by the nerve that's affected by the tumor.

When to see a doctor

Make an appointment with a doctor or other healthcare professional if you have symptoms that worry you.

Malignant peripheral nerve sheath tumors (MPNSTs) are caused by DNA changes in cells in the covering on nerves. Exactly what causes the DNA changes that lead to MPNST isn't always known.

A cell's DNA holds the instructions that tell a cell what to do. In healthy cells, the DNA gives instructions to multiply at a set rate. The instructions also tell the cells to die off at a set time. In cancer cells, changes happen in the DNA. The changes alter the instructions for multiplying and dying. The result is that the cancer cells multiply faster than healthy cells. And they can keep living when healthy cells would die. This causes too many cells in the area.

With a malignant peripheral nerve sheath tumor, the cancer cells build up in the covering on a nerve. Over time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it's called metastatic cancer. Malignant peripheral nerve sheath tumors most often spread to the lungs. They also can spread to the liver, bones and brain.

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

• A history of radiation therapy for cancer. Rarely, a malignant peripheral nerve sheath tumor can form in an area treated with radiation therapy. The tumors tend to develop 10 to 20 years after radiation treatment.
• Benign nerve sheath tumors. MPNSTs can develop from benign peripheral nerve tumors, such as neurofibromas.
• Neurofibromatosis type 1 (NF1). NF1 causes changes in skin pigment and the growth of tumors on nerve tissue. This genetic condition is caused by DNA changes that happen before birth. These DNA changes also increase the risk of MPNSTs. In people with NF1, these tumors tend to happen at a younger age and grow larger than those that happen in people without this condition.

To diagnose a malignant peripheral nerve sheath tumor (MPNST), a healthcare professional may start with an exam and imaging tests. To be certain whether something detected on those tests is cancer, the health professional may recommend a biopsy procedure to remove some tissue for testing.

Neurological exam

A neurological exam tests the brain and nerves to see how they're working. This exam may include checking your vision, hearing, balance, coordination, strength and reflexes. If you have trouble in one or more areas, this may give your healthcare professional clues about what's causing your symptoms. A neurological exam can't diagnose malignant peripheral nerve sheath tumors. But it helps your health professional understand whether your symptoms may be related to a nerve condition.

Imaging tests

Imaging tests make pictures of the body. The pictures might help healthcare professionals see the size of the MPNST and whether it has spread to other parts of the body. Tests might include:

• Magnetic resonance imaging (MRI).
• Computerized tomography (CT).
• Positron emission tomography (PET).

On MRI scans, a malignant peripheral nerve sheath tumor may look like a growth that is wide in the middle and narrow at both ends. These tumors also can look round or have an irregular shape.

Biopsy

A biopsy is a procedure to remove a sample of tissue for testing in a lab. To get a tissue sample from a malignant peripheral nerve sheath tumor, the healthcare team may recommend surgery to remove some or all of the tumor. Sometimes a healthcare professional may put a needle through the skin to get a sample. Imaging tests help guide the needle to the right spot.

Healthcare professionals in the lab look at the sample to see if it is cancer. Other tests might give more details about the cancer cells. The healthcare team uses this information to make a treatment plan.

Grades

The cancer's grade tells the healthcare team how the cancer is likely to behave. To determine the grade for malignant peripheral nerve sheath tumors, healthcare professionals in the lab examine a sample of the cancer under a microscope. They look at how the cancer cells appear and how many cells are dividing. They also look at how much of the cancer contains dead cells. These features are used to assign a grade from 1 to 3.

MPNST grades include:

• Grade 1. The cancer is low grade and is likely to grow slowly.
• Grade 2. The cancer is intermediate grade and is likely to grow more quickly than grade 1 cancer.
• Grade 3. The cancer is high grade. It's more likely to grow quickly and to spread to other parts of the body.

Most malignant peripheral nerve sheath tumors are high-grade cancers.

Stages

The cancer stage tells the healthcare team about the size of the cancer and whether it has spread. The stage helps the care team make a treatment plan. MPNST stages are based on the size of the cancer, whether it has spread and the grade. This information can come from imaging tests, results from a biopsy and findings from surgery to remove the cancer.

MPNST is a type of soft tissue sarcoma. MPNST staging uses the same stages as soft tissue sarcoma. There are different sets of stages based on where the cancer happens in the body. Most malignant peripheral nerve sheath tumors happen in the arms, legs and trunk. The stages for these cancers are:

• Stage 1. The cancer is low grade and can be any size. At this stage, the cancer hasn't spread.
• Stage 2. The cancer is intermediate or high grade and is 5 centimeters (about 2 inches) or smaller. The cancer hasn't spread.
• Stage 3. The cancer is intermediate or high grade and is larger than 5 centimeters. It hasn't spread.
• Stage 4. The cancer has spread to nearby lymph nodes or to other parts of the body. When cancer spreads, it's called metastatic cancer. MPNST most often spreads to the lungs. It also can spread to the liver, bones and brain.

If your malignant peripheral nerve sheath tumor starts in a part of the body other than the arms, legs or trunk, your healthcare team may use a different set of stages.

Treatment for malignant peripheral nerve sheath tumors (MPNSTs) often involves surgery to remove the cancer. Other treatments may include radiation therapy and chemotherapy.

Surgery

The goal of surgery for malignant peripheral nerve sheath tumors is to remove all of the tumor and some of the healthy tissue around it. Whether surgeons can remove the tumor completely may depend on the tumor's size and location.

To get all of the cancer cells, surgeons may need to remove nearby nerves or other structures. For tumors in the arms and legs, this sometimes means removing the arm or leg, though surgeons avoid this when possible.

Radiation therapy is sometimes used before surgery. This might help shrink the tumor and make it more likely that the tumor can be removed completely.

Radiation therapy

Radiation therapy treats cancer with powerful energy beams. 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.

For malignant peripheral nerve sheath tumors, radiation might be used after surgery. It can kill any cancer cells that might remain. Sometimes radiation is used before surgery.

Chemotherapy

Chemotherapy treats cancer with strong medicines. Not all malignant peripheral nerve sheath tumors respond to chemotherapy. This treatment might be an option when the cancer spreads. Chemotherapy may help slow the growth of the cancer and help with symptoms, such as pain.

The prognosis for malignant peripheral nerve sheath tumors (MPNSTs) varies widely. A cancer prognosis describes how likely it is that a cancer can be treated successfully or cured. It's based on what the healthcare team knows about the cancer, the treatment options and your overall health.

In general, malignant peripheral nerve sheath tumors that can be removed completely with surgery have the most favorable outlook. Removing all of the cancer lowers the risk that the cancer will come back or spread.

If you want to know more about your outlook or wonder what your cancer means for your life expectancy, talk with your healthcare team. Your healthcare professionals can explain what factors they consider when thinking about your prognosis.

Your healthcare team may consider:

• The cancer's grade. High-grade cancers tend to grow more quickly and are more likely to spread.
• The cancer's location. Some tumors, such as those growing in the head and neck area, may be more difficult to remove completely.
• The cancer's size. Larger tumors have a greater risk of spreading.
• Results of surgery. The outlook is generally more favorable when surgeons can remove all of the cancer.
• Whether the cancer has spread. The cancer may be more difficult to control if it spreads to other parts of the body.

These factors provide general information about prognosis, but they cannot predict exactly what will happen for one person. Your healthcare team can explain what these factors mean for you.

If you have symptoms that worry you, make an appointment with a doctor or other healthcare professional.

People who are diagnosed with malignant peripheral nerve sheath tumors (MPNSTs) may receive care from:

• Neurologists. These doctors diagnose and treat nervous system conditions.
• Neurosurgeons. These surgeons do operations involving the nerves.
• Oncologists. These doctors treat cancer.
• Orthopedic surgeons. These surgeons do operations involving the bones.

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 given during an appointment. Someone who is with 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 healthcare professional.

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 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 other health conditions. How can I 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 healthcare professional 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?