Malignant peripheral nerve sheath tumor (MPNST)

Malignant peripheral nerve sheath tumors (MPNST) are exceedingly rare. They can occur at any age and on any part of the body, although they’re most likely to be found on large nerves associated with the arms, legs or pelvis. They often grow on one of the sciatic nerves, which start at the spine and travel through the hip and down the back of your legs.

What is a malignant peripheral nerve sheath tumor (MPNST)?

Malignant peripheral nerve sheath tumors are a type of soft tissue sarcoma – cancers that grow in soft tissues of the body like muscles, fat, blood vessels and nerves. MPNST cancers grow on the nerve sheath – the covering that protects the parts of nerves that allow messages to travel between your central nervous system (brain and spine) to locations all over your body.

Malignant peripheral nerve sheath tumors are cancerous. MPNSTs grow quickly and may be resistant to treatment. They tend to return after being removed through surgery or other treatments. When they return, they’re also known to spread, or metastasize, to the lungs.

Malignant peripheral nerve sheath tumors are peripheral nerve tumors. A small number of MPNST cancers grow from previously benign neurofibroma or schwannoma tumors.

We don’t know what causes malignant peripheral nerve sheath tumors. Recent research has discovered links to genes in these cancers that may lead to more effective therapies.

Malignant peripheral nerve sheath tumor symptoms

Like other kinds of tumors, malignant peripheral nerve sheath tumors may not have symptoms when they’re small. Symptoms often start after they’ve grown bigger and may include:

• Pain, tingling or weakness in the affected area
• Growing lump under the skin
• Changes in sensitivity to touch, temperature or pain

Malignant peripheral nerve sheath tumor risk factors

Malignant peripheral nerve sheath tumors are most common in young and middle-aged adults. People who have a genetic condition called neurofibromatosis type 1 make up about 50% of those diagnosed with a malignant peripheral nerve sheath tumor. Having had previous exposure to radiation, either environmental or through radiation treatment, is another risk factor.

Some malignant peripheral nerve sheath tumors happen randomly without any known risk factors..

How is a malignant peripheral nerve sheath tumor diagnosed?

Since MPNST cancers are rare, your doctor will also consider more common conditions that could be causing your symptoms. They’ll perform a complete physical and examine any lumps that can be seen or felt.

If the exam or your symptoms point toward a neuromuscular disorder, tests will be performed to see if your condition is affecting your reflexes or movements. If your symptoms indicate you may have neurofibromatosis type 1, your doctor may suggest genetic testing to verify this condition.

Imaging tests such as MRI, CT or PET will be performed to determine the size and location of any tumors and whether they have spread to other areas.

Once the location of a tumor is confirmed, we may use a needle to extract tissue for a biopsy which will allow microscopic evaluation of the tissue and molecular testing. Some tumors require a short surgery to obtain a biopsy because they’re located in places where a needle biopsy won’t work.

Your doctor will use all this information to diagnose your condition.

How is a malignant peripheral nerve sheath tumor treated?

Removing the tumor is the goal of malignant peripheral nerve sheath tumor treatment. Surgery will be used to remove as much of the nerve as possible. These surgeries are complex because they need to be done while minimizing damage to the nerves. When the malignant peripheral nerve sheath tumor is on an arm or leg, amputation is sometimes needed.

If imaging indicates the tumor can’t be completely removed, you may receive chemotherapy before surgery to help shrink the tumor and make it easier to remove. Radiation therapy may also be used to shrink your tumor before surgery.

Either chemotherapy or radiation may also be used after surgery to remove any part of the tumor that wasn’t able to be removed or to treat cancer that has spread to other areas of your body.

Treatment for cancer isn’t limited to the medical side of things. We provide wellness support to help with things like:

• Physical therapy to support strength and range of motion
• Nutritional counseling
• Emotional counseling
• Spiritual counseling
• Support for sexual wellbeing
• Palliative care and hospice care

We provide care to enhance your quality of life during your treatment and afterward.