Overview
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.
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Symptoms
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.
Causes
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.
Risk factors
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.
Aug. 14, 2026