What Is a Malignant Peripheral Nerve Sheath Tumor? A Plain-Language Guide to This Rare Cancer

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

Quick Answer: Key Facts About Malignant Peripheral Nerve Sheath Tumors

A malignant peripheral nerve sheath tumor is a rare cancer that starts in the protective covering of a peripheral nerve, mostly in the deep tissue of the arms, legs and trunk. It most often spreads to the lungs. Surgery is the main treatment, and complete removal gives the greatest chance of cure, sometimes with radiation or chemotherapy.

Feature	Details
What it is	A rare cancer that starts in the protective covering of a peripheral nerve, the nerves that run from the spinal cord into the body. [1]
Where it forms	Anywhere in the body, but mostly in the deep tissue of the arms, legs, and trunk. It starts in the nerve covering, not in the nerve fiber itself. [1]
Benign or malignant	Malignant means cancerous. Not all nerve sheath growths are cancers, and benign ones usually grow slowly and do not spread. [1]
Spread	Most often to the lungs, and also to the liver, bones, and brain. [1]
Main treatment	Surgery. Complete removal gives the greatest chance for a cure, and radiation therapy and chemotherapy may also be used. [1] [2]

What the research says

• Survival and local recurrence are poor, and complete removal is the main protective factor. A meta-analysis of 28 studies found pooled 5-year overall survival of 49%, 5-year event-free survival of 37%, and a local recurrence rate of 38%. Worse outcomes were linked to NF1, large size, deep location, high grade, metastases, and trunk or head and neck location, while complete resection with adequate margins was the mainstay protective factor. (Cai et al., World J Surg Oncol, 2020) [3]

• Radiation-induced MPNSTs appeared about 12 to 14 years after radiotherapy. A systematic review of 65 radiation-induced and 26 radiation-associated MPNSTs in people with neurofibromatosis found mean latency periods of 13.5 and 11.8 years, respectively, and a prognosis worse than reported for MPNSTs that arise without prior radiation. (Yamanaka and Hayano, World Neurosurg, 2017) [4]

• The evidence for the best treatment combination is limited. A systematic review of 50 patients with NF1-associated MPNST across 12 observational studies found that patients had surgery alone (21), surgery plus chemotherapy (10), surgery plus radiotherapy (7), or all three (12). The authors concluded that the quality of evidence on optimal treatment remains tenuous and that the roles of chemotherapy and radiotherapy are unclear. (Tora et al., Neurosurg Rev, 2020) [5]

What Is a Malignant Peripheral Nerve Sheath Tumor?

A malignant peripheral nerve sheath tumor (MPNST) is a rare cancer that starts 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. [1]

MPNST can happen anywhere in the body. It mostly occurs in the deep tissue of the arms, legs, and trunk. [1]

Figure 1: How an MPNST forms: the cancer starts in the thin covering around a nerve, not in the nerve fiber itself.

What Are the Symptoms of MPNST?

Malignant peripheral nerve sheath tumors may cause signs and symptoms that get worse quickly. [1]

Symptom	What it looks like
A new lump	A new, growing lump of tissue under the skin.
Fast growth in an existing lump	A benign nerve tumor that was not growing, or was growing slowly, suddenly grows faster.
Sensation changes	A burning or tingling feeling in the area of the tumor.
Pain	Pain where the tumor is growing.
Weakness	Weakness when trying to move the body part that has the tumor, or muscles controlled by the affected nerve.

When should you see a doctor?

Make an appointment with a doctor or other healthcare professional if you have symptoms that worry you. A lump that is new, growing, or painful, especially one that causes tingling, burning, or weakness in the same area, deserves a medical evaluation. [1]

What Causes Malignant Peripheral Nerve Sheath Tumors?

Malignant peripheral nerve sheath tumors are caused by DNA changes in cells in the covering on nerves. Exactly what causes the DNA changes that lead to MPNST is not always known. [1]

A cell's DNA holds the instructions that tell a cell what to do. In healthy cells, DNA gives instructions to multiply at a set rate and to die off at a set time. In cancer cells, changes in the DNA alter these instructions. Cancer cells multiply faster than healthy cells and can keep living when healthy cells would die. This causes too many cells in the area. [1]

Figure 2: The chain of events inside a nerve covering cell: DNA changes break the normal instructions for when cells multiply and die, so too many cells build up and form a tumor.

Why do these tumors grow so quickly?

The answer is in the DNA changes described above. Because cancer cells multiply faster than healthy cells and outlive the time when healthy cells would die, the tumor builds up fast. That is also why MPNST symptoms tend to get worse quickly instead of staying stable for years.

Can MPNST Spread to Other Parts of the Body?

Yes. Over time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it is called metastatic cancer. Malignant peripheral nerve sheath tumors most often spread to the lungs. They also can spread to the liver, bones, and brain. [1]

Is MPNST a Benign or Malignant Nerve Tumor?

MPNST is called malignant because it is 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. The difference is how those cells behave over time. [1]

Feature	Benign nerve sheath tumor	Malignant peripheral nerve sheath tumor
Cancerous?	No	Yes
Growth speed	Usually grows slowly	Tends to grow quickly
Ability to spread	Does not spread	Can spread to other parts of the body, most often the lungs

What Is the Difference Between MPNST and Soft Tissue Sarcoma?

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 is malignant schwannoma, which refers to the fact that MPNST often involves nerve sheath cells called Schwann cells. [1]

Who Is at Risk for MPNST?

Three factors increase the risk of malignant peripheral nerve sheath tumors. [1]

Risk factor	What it means
A history of radiation therapy for cancer	Rarely, an MPNST 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 is a genetic condition caused by DNA changes that happen before birth. It causes changes in skin pigment and the growth of tumors on nerve tissue. In people with NF1, these tumors tend to happen at a younger age and grow larger than those in people without this condition.

How Is MPNST Diagnosed?

To diagnose a malignant peripheral nerve sheath tumor, 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. [2]

What tests are used to diagnose MPNST?

Test	What it does
Neurological exam	Checks how the brain and nerves are working: vision, hearing, balance, coordination, strength, and reflexes. It cannot diagnose MPNST, but it helps the professional see whether symptoms may be related to a nerve condition.
MRI (magnetic resonance imaging)	Makes pictures of the body to show the size of the tumor and whether it has spread. On MRI, an MPNST may look wide in the middle and narrow at both ends, round, or irregular in shape.
CT (computerized tomography)	Makes detailed pictures of the body to help see tumor size and whether it has spread.
PET (positron emission tomography)	Another imaging test that helps healthcare professionals see whether the cancer has spread.
Biopsy	A procedure to remove a sample of tissue for testing in a lab. It may involve surgery to remove some or all of the tumor, or a needle through the skin guided by imaging. The lab checks whether the sample is cancer and gathers details about the cancer cells.

How are MPNSTs graded?

The cancer's grade tells the healthcare team how the cancer is likely to behave. Lab professionals examine a sample of the cancer under a microscope. They look at how the cancer cells appear, how many cells are dividing, and how much of the cancer contains dead cells. These features are used to assign a grade from 1 to 3. [2]

Grade	What it means
Grade 1	Low grade. The cancer is likely to grow slowly.
Grade 2	Intermediate grade. The cancer is likely to grow more quickly than grade 1 cancer.
Grade 3	High grade. The cancer is more likely to grow quickly and to spread to other parts of the body.

Most malignant peripheral nerve sheath tumors are high-grade cancers. [2]

How are MPNSTs staged?

The cancer stage tells the healthcare team about the size of the cancer and whether it has spread. MPNST staging uses the same stages as soft tissue sarcoma, with different sets of stages based on where the cancer happens in the body. Most MPNSTs happen in the arms, legs, and trunk. [2]

Stage	What it means
Stage 1	Low grade and any size. The cancer has not spread.
Stage 2	Intermediate or high grade, and 5 centimeters (about 2 inches) or smaller. The cancer has not spread.
Stage 3	Intermediate or high grade, and larger than 5 centimeters. The cancer has not spread.
Stage 4	The cancer has spread to nearby lymph nodes or to other parts of the body. MPNST most often spreads to the lungs, and also can spread to the liver, bones, and brain.

If an MPNST starts in a part of the body other than the arms, legs, or trunk, the healthcare team may use a different set of stages. [2]

How Is a Malignant Peripheral Nerve Sheath Tumor Treated?

Treatment for MPNST often involves surgery to remove the cancer. Other treatments may include radiation therapy and chemotherapy. [2]

Figure 3: The main treatment options for MPNST: surgery, radiation therapy, and chemotherapy are often used together, and the plan depends on the tumor's size, location, grade, and stage.

What is the goal of surgery for MPNST?

The goal of surgery 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. [2]

Surgery is the main treatment for MPNST. When the cancer can be removed completely, this gives the greatest chance for a cure. [1]

When is radiation therapy used?

Radiation therapy treats cancer with powerful energy beams. The energy can come from X-rays, protons, or other sources. During treatment, you lie on a table while a machine moves around you and directs radiation to precise points on your body. For MPNST, radiation might be used after surgery to kill any cancer cells that might remain. Sometimes radiation is used before surgery. That can help shrink the tumor and make it more likely that the tumor can be removed completely. [2]

When is chemotherapy used?

Chemotherapy treats cancer with strong medicines. Not all MPNSTs 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. [2]

What happens when the cancer cannot be fully removed?

MPNSTs often come back after surgery or spread despite treatment. Sometimes the cancer happens in a place where it is hard to remove completely. When the cancer spreads or cannot be removed completely, treatments can help slow the growth and help with symptoms, such as pain. [1]

What Is the Outlook for Someone With MPNST?

The prognosis for MPNST varies widely. A cancer prognosis describes how likely it is that a cancer can be treated successfully or cured. It is based on what the healthcare team knows about the cancer, the treatment options, and the person's overall health. In general, MPNSTs 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. [2]

Factor	How it affects the outlook
Grade	High-grade cancers tend to grow more quickly and are more likely to spread.
Location	Some tumors, such as those growing in the head and neck area, may be more difficult to remove completely.
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. If you want to know more about your outlook, talk with your healthcare team. [2]

Who Is on the Care Team for MPNST?

People diagnosed with MPNST may receive care from a team of specialists: [2]

• Neurologists: Doctors who diagnose and treat nervous system conditions.

• Neurosurgeons: Surgeons who do operations involving the nerves.

• Oncologists: Doctors who treat cancer.

• Orthopedic surgeons: Surgeons who do operations involving the bones.

What questions should you ask at your appointment?

Appointments can be brief, and there is a lot to discuss. Asking a family member or friend to come along can help you remember the information. Questions to ask at the first appointment include: [2]

• What may be causing my symptoms? Are there other possible causes?

• What tests do I need?

• What is the next step in finding my diagnosis and deciding on treatment?

• Are there restrictions I need to follow in the meantime?

Questions to ask a specialist include:

• Do I have a malignant peripheral nerve sheath tumor?

• What are the goals of treatment for me, and 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 does not work, what is next?

• What is the outlook for my condition?

Your healthcare professional is likely to ask you questions too, such as: Have your symptoms changed over time? Does anything make your symptoms better or worse? Have you been told you have other medical conditions? [2]

Talk with a healthcare professional. If you notice a lump that is growing, painful, or causing tingling or weakness, make an appointment with a doctor or other healthcare professional. For more evidence-based health guides, visit Rinnit.com.

Frequently Asked Questions

Is a malignant peripheral nerve sheath tumor cancerous?

Yes. "Malignant" means the tumor is cancerous. However, not all growths in nerve coverings are cancers, because some are benign (noncancerous). Benign nerve tumors usually grow slowly and do not spread, while malignant ones tend to grow quickly and can spread. [1]

Where do malignant peripheral nerve sheath tumors usually form?

Malignant peripheral nerve sheath tumors can happen anywhere in the body but mostly occur in the deep tissue of the arms, legs, and trunk. [1]

Where does MPNST spread?

Malignant peripheral nerve sheath tumors most often spread to the lungs. They also can spread to the liver, bones, and brain. [1]

What is the main treatment for MPNST?

Surgery is the main treatment. The goal is to remove all of the tumor plus some of the healthy tissue around it. When the cancer can be removed completely, this gives the greatest chance for a cure. Radiation therapy and chemotherapy may also be used. [1] [2]

Does chemotherapy work for MPNST?

Not always. Not all MPNSTs respond to chemotherapy. It might be an option when the cancer spreads, and it may help slow the cancer's growth and ease symptoms such as pain. [2]

Is MPNST linked to radiation therapy or neurofibromatosis?

In some cases, yes. Rarely, an MPNST can form in an area treated with radiation therapy, and these tumors tend to develop 10 to 20 years after treatment. MPNSTs can also develop from benign nerve tumors, and people with neurofibromatosis type 1 (NF1), a genetic condition, have a higher risk, with tumors that tend to happen at a younger age and grow larger. [1]

What does the grade of an MPNST mean?

The grade, from 1 to 3, describes how the cancer is likely to behave. Grade 1 is low grade and likely to grow slowly. Grade 2 is intermediate grade. Grade 3 is high grade and more likely to grow quickly and spread. Most MPNSTs are high-grade cancers. [2]

What is the difference between MPNST and malignant schwannoma?

Malignant schwannoma is an older name for the same condition. It refers to the fact that MPNST often involves Schwann cells, which are nerve sheath cells. In the past, MPNST was also known as neurofibrosarcoma. [1]

Related Reading

• What Is Malignant Hyperthermia? The Anesthesia Reaction That Runs in Families

Conclusion

Malignant peripheral nerve sheath tumors are rare cancers that form in the protective covering of nerves running from the spinal cord into the body. They usually appear in the deep tissue of the arms, legs, or trunk as a lump that grows quickly, causes pain, or brings tingling, burning, or weakness along the affected nerve. Most are high grade. Surgery to remove the tumor completely offers the best chance of cure, with radiation therapy and chemotherapy used before or after surgery depending on the tumor's size, location, grade, and stage. Because MPNSTs can return or spread, ongoing follow-up and early attention to new or worsening symptoms matter.

References

1. Mayo Clinic Staff. Malignant peripheral nerve sheath tumors (MPNSTs) - Symptoms and causes. Mayo Clinic. August 17, 2026. https://www.mayoclinic.org/diseases-conditions/malignant-peripheral-nerve-sheath-tumors/symptoms-causes/syc-20362603

2. Mayo Clinic Staff. Malignant peripheral nerve sheath tumors (MPNSTs) - Diagnosis and treatment. Mayo Clinic. August 17, 2026. https://www.mayoclinic.org/diseases-conditions/malignant-peripheral-nerve-sheath-tumors/diagnosis-treatment/drc-20362619

3. Cai Z, et al. Prognosis and risk factors for malignant peripheral nerve sheath tumor: a systematic review and meta-analysis. World Journal of Surgical Oncology. 2020;18(1):257. PMID 32998743. https://doi.org/10.1186/s12957-020-02036-x

4. Yamanaka R, et al. Radiation-Induced Malignant Peripheral Nerve Sheath Tumors: A Systematic Review. World Neurosurgery. 2017;105:961-970.e8. PMID 28602926. https://doi.org/10.1016/j.wneu.2017.06.010

5. Tora MS, et al. Treatment of neurofibromatosis 1-associated malignant peripheral nerve sheath tumors: a systematic review. Neurosurgical Review. 2020;43(4):1039-1046. PMID 31209658. https://doi.org/10.1007/s10143-019-01135-y

Medical disclaimer

This article is for educational purposes only and is not intended as medical advice. Always consult a qualified healthcare professional for diagnosis and treatment decisions.