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A nerve sheath tumor is a type of tumor of the nervous system (nervous system neoplasm) which is made up primarily of the myelin surrounding nerves. Nerve sheath tumors can be benign or malignant , and may affect both the peripheral and central nervous systems .
A malignant peripheral nerve sheath tumor (MPNST) is a form of cancer of the connective tissue surrounding peripheral 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]
New and more precisely defined entities include malignant melanotic nerve sheath tumor (formerly known as melanotic schwannoma) and hybrid nerve sheath tumors. [4] [5] The majority of peripheral nerve tumors are benign tumors of the nerve sheath (usually schwannomas); on rare occasions, they are metastatic tumors or originate from the nerve cells.
The overall incidence rate of brain tumors in children is 6.2 per 100,000. [10] Glioblastomas are the most aggressive malignant glioma and make up approximately 47.7% of all gliomas, and are more commonly found in males. [10] [16] Their incidence rate is 3.23 per 100,000 people. [10] The 5-year survival rate for glioblastoma is only 6.8%. [10]
Meningiomas, which develop in the meninges, are common primary brain tumors, representing approximately 37% of all brain tumors. [15] The incidence rate for meningiomas is 9.51 per 100,000 people. [9] Unlike gliomas, more than 98% of meningiomas are nonmalignant [15]. The 5-year survival rate for nonmalignant meningiomas is approximately 91%. [9]
Malignant peripheral nerve sheath tumor (includes epithelioid variety) ... Pediatric rhabdomyosarcoma patients have a 50–85% long term survival rate. [23]
Malignant melanotic nerve sheath tumor (previously known as melanotic schwannoma) is a rare aggressive peripheral nerve sheath tumor that typically develops in conjunction with spinal or visceral autonomic nerves, consisting uniformly of Schwann cells displaying melanocytic differentiation.
PNI and PNS are considered an unfavorable prognostic factors in head and neck cancer of virtually all sites, associated with poor local and regional disease control, probability of locoregional and distant metastases, disease recurrence, and lower survival rate. Although adenoid cystic carcinoma accounts for only 1-3% of head and neck tumors ...