A malignant peripheral nerve sheath tumor (MPNST) is a tumor that develops in the protective lining that covers nerves. The first symptom of MPNST is often a lump or mass that increases in size, sometimes causing pain or a tingling sensation. MPNST is considered an aggressive tumor because there is up to a 65% chance of the tumor regrowing after surgery (a recurrence), and approximately 40% chance of spreading to distant parts of the body (a metastasis), most commonly to the lung. Treatment of MPNST begins with surgery to remove as much of the tumor as possible. Radiation therapy may be used to decrease the chance of a recurrence. Chemotherapy might be used if the whole tumor cannot be removed during surgery, or to treat a metastasis. MPNSTs are quite rare, occurring in 0.001% of the general population.  Approximately 25-50% of MPNSTs are associated with a genetic condition known as neurofibromatosis type 1.

Malignant peripheral nerve sheath tumors (MPNST) are aggressive tumors. The chance of surviving a diagnosis of MPNST depends on the size and location of the tumor; people who have a small tumor tend to survive longer than those with a large tumor, and people with a tumor in the arms or legs tend to survive longer those with a tumor in the head and neck regions. Also, MPNSTs that are treated when they first occur have a better prognosis than when the tumor has regrown after initial treatments (recurred) or spread to distant parts of the body (metastasized). One study of 140 patients found that 26% of individuals diagnosed with MPNST were living 10 years after the initial diagnosis. Of those patients who developed a metastasis, 8% were living 10 years after the initial diagnosis.