| Peripheral nerve tumor | |
|---|---|
 | |
| MRI (coronal plane) showing the site of MPNST in the left tibia. | |
| Specialty | Neurosurgery |
Peripheral nerve tumors, also called tumors of peripheral nerves or tumors of the peripheral nervous system, are a diverse category with a range of morphological characteristics and biological potential. [1] They are categorized as either benign or malignant peripheral nerve sheath tumors. [2] [3]
They vary from benign (soft tissue perineurioma and schwannoma) that can be completely removed to benign (plexiform neurofibroma) that may be locally aggressive to extremely malignant (malignant peripheral nerve sheath tumors [MPNST]). [1] 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. [6] [7]
Most peripheral nerve tumors occur for unknown reasons. Some, including schwannomatosis and neurofibromatosis (types 1 and 2), are associated with recognized hereditary disorders. Others may be caused by gene mutations. In the case of schwannomatosis and neurofibromatosis, tumors can grow on or close to nerves anywhere in the body. Frequently, there are several tumors. [8]
The typical symptoms involve a combination of pain, loss of nerve function, and/or a palpable (or radiographically apparent) mass affecting a peripheral nerve. The etiology and importance of the last two symptoms should be apparent. For example, the presence of a severe nerve palsy is highly suggestive of malignancy as it is most likely the result of the tumor invading and destroying nerves. [7]
Methods used to identify tumors of the peripheral nervous system include a family history of any predisposition syndrome, including neurofibromatosis types 1 and 2, a targeted and comprehensive physical examination, and radiological investigations, the primary one being magnetic resonance imaging. [9] [10] Other radiological investigations may include plain radiographs, ultrasound examination, computed tomography, and positron emission tomography. [11] Definitive diagnosis is made by tumor biopsy. [12] Surgery is the most common method of treating peripheral nerve sheath tumors. [11] In malignant tumors, complete resection is the only known curative treatment (with a sufficiently wide margin or even amputation to improve prognosis). [12] For larger lesions or those with a more aggressive histology, adjuvant radiation is recommended. Novel or combination therapies that are the focus of ongoing clinical trials are highly desirable. [13] [14]
Formally, the majority of these tumors lack a CNS WHO grade; instead, neoplasms should be graded within each category of tumor. [5]
| Tumor type | Malignancy | Estimated incidence | Location |
|---|---|---|---|
| Schwannoma | Benign | 1.09 per 100,000/year |
|
| Neurofibroma (Localized, diffuse, plexiform subtype) | Benign | 5.3% of all benign soft tissue tumors |
|
| Perineurioma (Intraneural and soft tissue subtypes) | Benign | 1% of nerve sheath and soft tissue neoplasms, respectively (>50 cases of intraneural perineuriomas and >300 cases of soft tissue perineuriomas have been described) |
|
| Hybrid nerve sheath tumor | Benign | Very rare |
|
| Malignant peripheral nerve sheath tumour (MPNST) (epithelioid and perineural subtypes) | Malignant | 2–10% of soft tissue sarcomas. Epithelioid MPNST is particularly rare (~5% of all MPNST) |
|
| Malignant melanotic nerve sheath tumour (MMNST) | Malignant | Very rare |
|
| Neuroendocrine tumour (previously paraganglioma) | Malignant | Very rare |
|
A brain tumor occurs when abnormal cells form within the brain. There are two main types of tumors: malignant (cancerous) tumors and benign (non-cancerous) tumors. These can be further classified as primary tumors, which start within the brain, and secondary tumors, which most commonly have spread from tumors located outside the brain, known as brain metastasis tumors. All types of brain tumors may produce symptoms that vary depending on the size of the tumor and the part of the brain that is involved. Where symptoms exist, they may include headaches, seizures, problems with vision, vomiting and mental changes. Other symptoms may include difficulty walking, speaking, with sensations, or unconsciousness.
Neurofibromatosis (NF) refers to a group of three distinct genetic conditions in which tumors grow in the nervous system. The tumors are non-cancerous (benign) and often involve the skin or surrounding bone. Although symptoms are often mild, each condition presents differently. Neurofibromatosis type I (NF1) is typically characterized by café au lait spots, neurofibromas, scoliosis, and headaches. Neurofibromatosis type II (NF2), on the other hand, may present with early-onset hearing loss, cataracts, tinnitus, difficulty walking or maintain balance, and muscle atrophy. The third type is called schwannomatosis and often presents in early adulthood with widespread pain, numbness, or tingling due to nerve compression.
A vestibular schwannoma (VS), also called acoustic neuroma, is a benign tumor that develops on the vestibulocochlear nerve that passes from the inner ear to the brain. The tumor originates when Schwann cells that form the insulating myelin sheath on the nerve malfunction. Normally, Schwann cells function beneficially to protect the nerves which transmit balance and sound information to the brain. However, sometimes a mutation in the tumor suppressor gene, NF2, located on chromosome 22, results in abnormal production of the cell protein named Merlin, and Schwann cells multiply to form a tumor. The tumor originates mostly on the vestibular division of the nerve rather than the cochlear division, but hearing as well as balance will be affected as the tumor enlarges.
Spinal tumors are neoplasms located in either the vertebral column or the spinal cord. There are three main types of spinal tumors classified based on their location: extradural and intradural. Extradural tumors are located outside the dura mater lining and are most commonly metastatic. Intradural tumors are located inside the dura mater lining and are further subdivided into intramedullary and extramedullary tumors. Intradural-intramedullary tumors are located within the dura and spinal cord parenchyma, while intradural-extramedullary tumors are located within the dura but outside the spinal cord parenchyma. The most common presenting symptom of spinal tumors is nocturnal back pain. Other common symptoms include muscle weakness, sensory loss, and difficulty walking. Loss of bowel and bladder control may occur during the later stages of the disease.
Meningioma, also known as meningeal tumor, is typically a slow-growing tumor that forms from the meninges, the membranous layers surrounding the brain and spinal cord. Symptoms depend on the location and occur as a result of the tumor pressing on nearby tissue. Many cases never produce symptoms. Occasionally seizures, dementia, trouble talking, vision problems, one sided weakness, or loss of bladder control may occur.
Glioblastoma, previously known as glioblastoma multiforme (GBM), is the most aggressive and most common type of cancer that originates in the brain, and has a very poor prognosis for survival. Initial signs and symptoms of glioblastoma are nonspecific. They may include headaches, personality changes, nausea, and symptoms similar to those of a stroke. Symptoms often worsen rapidly and may progress to unconsciousness.
Neurofibromatosis type I (NF-1), or von Recklinghausen syndrome, is a complex multi-system human disorder caused by the mutation of neurofibromin 1 (NF-1), a gene on chromosome 17 that is responsible for production of a protein (neurofibromin) which is needed for normal function in many human cell types. NF-1 causes tumors along the nervous system which can grow anywhere on the body. NF-1 is one of the most common genetic disorders and is not limited to any person's race or sex. NF-1 is an autosomal dominant disorder, which means that mutation or deletion of one copy of the NF-1 gene is sufficient for the development of NF-1, although presentation varies widely and is often different even between relatives affected by NF-1.
A synovial sarcoma is a rare form of cancer which occurs primarily in the extremities of the arms or legs, often in proximity to joint capsules and tendon sheaths. It is a type of soft-tissue sarcoma.
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%. MPNST with rhabdomyoblastomatous component are called malignant triton tumors.
Neurofibromatosis type II is a genetic condition that may be inherited or may arise spontaneously, and causes benign tumors of the brain, spinal cord, and peripheral nerves. The types of tumors frequently associated with NF2 include vestibular schwannomas, meningiomas, and ependymomas. The main manifestation of the condition is the development of bilateral benign brain tumors in the nerve sheath of the cranial nerve VIII, which is the "auditory-vestibular nerve" that transmits sensory information from the inner ear to the brain. Besides, other benign brain and spinal tumors occur. Symptoms depend on the presence, localisation and growth of the tumor(s). Many people with this condition also experience vision problems. Neurofibromatosis type II is caused by mutations of the "Merlin" gene, which seems to influence the form and movement of cells. The principal treatments consist of neurosurgical removal of the tumors and surgical treatment of the eye lesions. Historically the underlying disorder has not had any therapy due to the cell function caused by the genetic mutation.
A neurofibroma is a benign nerve-sheath tumor in the peripheral nervous system. In 90% of cases, they are found as stand-alone tumors, while the remainder are found in persons with neurofibromatosis type I (NF1), an autosomal-dominant genetically inherited disease. They can result in a range of symptoms from physical disfiguration and pain to cognitive disability.
Phakomatoses, also known as neurocutaneous syndromes, are a group of multisystemic diseases that most prominently affect structures primarily derived from the ectoderm such as the central nervous system, skin and eyes. The majority of phakomatoses are single-gene disorders that may be inherited in an autosomal dominant, autosomal recessive or X-linked pattern. Presentations may vary dramatically between patients with the same particular syndrome due to mosaicism, variable expressivity, and penetrance.
Schwannomatosis is an extremely rare genetic disorder closely related to the more-common disorder neurofibromatosis (NF). Originally described in Japanese patients, it consists of multiple cutaneous schwannomas, central nervous system tumors, and other neurological complications, excluding hallmark signs of NF. The exact frequency of schwannomatosis cases is unknown, although some populations have noted frequencies as few as 1 case per 1.7 million people.
A schwannoma is a usually benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves.
A nerve sheath tumor is a type of tumor of the nervous system which is made up primarily of the myelin surrounding nerves. From benign tumors like schwannoma to high grade malignant neoplasms known as malignant peripheral nerve sheath tumors, peripheral nerve sheath tumors include a range of clearly characterized clinicopathologic entities. A peripheral nerve sheath tumor (PNST) is a nerve sheath tumor in the peripheral nervous system. Benign peripheral nerve sheath tumors include schwannomas and neurofibromas.
The Ewing family of tumors (EFTs) is a group of small cell sarcomas including Ewing sarcoma of the bone, extra osseous Ewing tumors, and primitive neuroectodermal tumors. They are rare cancers, usually diagnosed in peoples' twenties. The sarcoma of bone is the most common of the variants. All forms are predisposed to metastasis and have had historically high rates of mortality. The family of tumors shares a common translocation mutation of the EWS gene on chromosome 22 to an ETS-type gene, most commonly the FLI1 gene. EFTs are highly malignant, with 5-year survival for patients with metastatic disease at 20%. The current standard of care includes resection, radiation, and chemotherapy.
Malignant triton tumor (MTT) is a relatively rare, aggressive tumor made up of both malignant schwannoma cells and malignant rhabdomyoblasts. It is classified as a malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation.
Neuro-oncology is the study of brain and spinal cord neoplasms, many of which are very dangerous and life-threatening. Among the malignant brain cancers, gliomas of the brainstem and pons, glioblastoma multiforme, and high-grade astrocytoma/oligodendroglioma are among the worst. In these cases, untreated survival usually amounts to only a few months, and survival with current radiation and chemotherapy treatments may extend that time from around a year to a year and a half, possibly two or more, depending on the patient's condition, immune function, treatments used, and the specific type of malignant brain neoplasm. Surgery may in some cases be curative, but, as a general rule, malignant brain cancers tend to regenerate and emerge from remission easily, especially highly malignant cases. In such cases, the goal is to excise as much of the mass and as much of the tumor margin as possible without endangering vital functions or other important cognitive abilities. The Journal of Neuro-Oncology is the longest continuously published journal in the field and serves as a leading reference to those practicing in the area of neuro-oncology.
Within medical ophthalmology, Intraocular schwannoma, also termed uveal schwannoma, is a type of schwannoma found in the eye. These tumors are almost always benign in nature and while malignant forms have been documented in other areas of the body, this has not been reported in the uveal region. Composed of Schwann cells, these masses are generally slow growing and can be found in the peripheral nerve tract, often around the head and neck.
An intraneural perineurioma is a rare benign tumor within the sheath of a single nerve that grows but typically does not recur or metastasize. These lesions are only composed of perineurial cells, cloned from a single cell. They are distinct from schwannoma and neurofibroma.