A malignant peripheral nerve sheath tumor (MPNST) (also known as "Malignant schwannoma,"[1] "Neurofibrosarcoma,"[1] and "Neurosarcoma"[1]) is a form of cancer of the connective tissue surrounding nerves. Given its origin and behavior it is classified as a sarcoma. About half the cases are diagnosed in people with neurofibromatosis; the lifetime risk for an MPNST in patients with neurofibromatosis type 1 is 8-13%.[2] MPNST with rhabdomyoblastomatous component are called malignant triton tumors.

The first-line treatment is surgical resection with wide margins. Chemotherapy (e.g. high-dose doxorubicin) and often radiotherapy are done as adjuvant and/or neoadjuvant treatment.