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. They are categorized as either benign or malignant peripheral nerve sheath tumors.

Description

They vary from benign (soft tissue perineurioma and

schwannoma A schwannoma (or neurilemmoma) is a usually benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves. Schwannomas are homogeneous tumors, consisting only of Schwann cells ...

) that can be completely removed to benign (

plexiform neurofibroma A neurofibroma is a benign nerve-sheath tumor in the peripheral nervous system. In 90% of cases, they are found as stand-alone tumors (solitary neurofibroma, solitary nerve sheath tumor or sporadic neurofibroma), while the remainder are found in ...

) that may be locally aggressive to extremely malignant ( malignant peripheral nerve sheath tumors PNST. New and more precisely defined entities include malignant melanotic nerve sheath tumor (formerly known as melanotic schwannoma) and hybrid nerve sheath tumors. 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. Most peripheral nerve tumors occur for unknown reasons. Some, including

schwannomatosis 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

neurofibromatosis 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, e ...

(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. The typical symptoms involve a combination of

pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...

, 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. 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 In a physical examination, medical examination, clinical examination, or medical checkup, a medical practitioner examines a patient for any possible medical signs or symptoms of a Disease, medical condition. It generally consists of a series of ...

, and radiological investigations, the primary one being

magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and ...

. Other radiological investigations may include plain

radiographs Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical ("diagnostic" radiography and "therapeu ...

ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...

examination,

computed tomography A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

, and

positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...

. Definitive diagnosis is made by tumor

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...

Surgery Surgery is a medical specialty that uses manual and instrumental techniques to diagnose or treat pathological conditions (e.g., trauma, disease, injury, malignancy), to alter bodily functions (e.g., malabsorption created by bariatric surgery s ...

is the most common method of treating peripheral nerve sheath tumors. In malignant tumors, complete resection is the only known curative treatment (with a sufficiently wide margin or even amputation to improve prognosis). 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.

Epidemiological and clinical features

Formally, the majority of these tumors lack a CNS WHO grade; instead, neoplasms should be graded within each category of tumor. {, class="wikitable" , +Peripheral nerve tumors !Tumor type !Malignancy !Estimated incidence !Location , - , Schwannoma , Benign , 1.09 per 100,000/year , * Skin and subcutaneous tissues of the head and neck, or along the flexor surfaces of the extremities * Spinal intradural extramedullary site with growth into foraminal space * Eight cranial nerve (bilateral involvement in NF2) , - , Neurofibroma (Localized, diffuse, plexiform subtype) , Benign , 5.3% of all benign soft tissue tumors , * Skin, with predominant dermal involvement, less frequently medium-sized nerves, a nerve plexus, a major nerve trunk, or spinal nerve roots * Bilateral and/or multiple spinal root involvement in NF1 * Spinal cord compression * Cranial nerve involvement is ultrarare , - , 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) , * Common presentation: focal, unilateral lesion affecting major peripheral nerves (sciatic, median, radial, brachial plexus) and their branches. * Uncommon locations: cranial nerves, lateral ventricle, oral cavity, skin, and mandible. Bilateral or unilateral multifocal lesions are rare , - , Hybrid nerve sheath tumor , Benign , Very rare , * The most common site is the fingers * Rare cases of cranial nerves involvement , - , 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) , * Extremities, trunk, head, and neck area , - , Malignant melanotic nerve sheath tumour (MMNST) , Malignant , Very rare , * Common sites are spinal or autonomic nerves near the midline * Uncommon sites: gastrointestinal tract, bone, soft tissues, heart, bronchus, liver, and skin , - , Neuroendocrine tumour (previously paraganglioma) , Malignant , Very rare , * Cauda equina region

References

Neurosurgery PNS neoplasia