Peripheral nerve sheath tumours (PNSTs) are tumours that arise from the protective layer of peripheral nerves. More specifically, they develop from nerve sheaths, which are layers of myelin and connective tissuea group of cells that work together to perform a function that provide insulation to nerve fibres within the nervous system.
The nervous system is made up of two primary components: the central nervous system (CNS), and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord, and is responsible for all sensory and motor functions in the body. The PNS encompasses all nerves outside of the CNS, and is responsible for all involuntary functions in the body. The PNS is further subdivided into the autonomic nervous system (ANS) and the somatic nervous system (SNS). The ANS controls involuntary processes and glands, such as heart rate, bloodthe red bodily fluid that transports oxygen and other nutrients around the body pressure, respiration, and digestion. Comparatively, the SNS is responsible for voluntary and involuntary muscle movements, as well as transmitting sensory information to the CNS.
This page will primarily focus on benignnot cancerous, can grow but will not spread to other body parts peripheral nerve sheath tumours (BPNSTs). BPNSTs are more common than malignantcancerous, may grow and spread to other areas of the body peripheral nerve sheath tumours (MPNSTs), however they can lead to nerve and/or muscle damage. In rare cases, BPNSTs can undergo a malignant transformation when left untreated. For more information on MPNSTs, please refer to the Rare Cancers Australia Peripheral Nerve Sheath Tumours (Malignant) page.
In general, the average age of diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results varies between BPNST subtypes.
Types of Benign Peripheral Nerve Sheath Tumours
There are several types of BPNSTs, which are categorised by the type of cellsthe basic structural and functional unit of all living things they develop from, and their cellular appearance under the microscope.
Schwannoma
Schwannomas, also known as neurinomas or neurilemmomas, are the most common BPNST in adults, and develop from Schwann cells in the PNS. Schwann cells are a type of glial (or supportive) cell that helps form the myelin sheath surrounding nerve fibres. Schwannomas are more common in people between the ages of 50 and 70, and tends to be diagnosed equally between the sexes.
For more information on schwannomas, please refer to the Rare Cancers Australia Schwannoma page.
Neurofibroma
Neurofibromas are a common type of BPNST that tends to develop along the nerves and contain fibrous or connective tissue. They are generally diagnosed equally among the sexes, and are often diagnosed between the ages of 20-40.
For more information on neurofibromas, please refer to the Rare Cancers Australia Neurofibroma page.
Perineuroma
Perineuromas are a rare type of BPNST that develops from perineural cells, a type of cell that surrounds the peripheral nerve sheath. These tumours are generally found in deeps soft tissues, the peripheral nerves of the limbs, or cranial nerves, however they can develop anywhere in the body. There are two main types of perineuroma, which are classified on their location and their proximity to large nerves.
Intraneural Perineuroma
Intraneural perineuromas are perineuromas that develop from within the nerve, such as peripheral nerves of the limbs and cranial nerves. These tumours are most commonly found in children and young adults, are generally benign, and can have a good prognosisto predict how a disease/condition may progress and what the outcome might be.
Extraneural Perineuroma
Extraneural perineuromas, also known as soft tissuetissue/the material that joins, holds up or surrounds inside body parts such as fat, muscle, ligaments and lining around joints perineuromas, are perineuromas that develop next to nerves, most notably deep in soft tissue. These tumours are not generally associated with large nerves nearby, and are generally diagnosed in patients between the ages of 16-70. Extraneural perineuromas are generally benign, and can have a good prognosis.
Hybrid Nerve Sheath Tumour
Hybrid nerve sheath tumours, also known as hybrid peripheral nerve sheath tumours (HPNSTs), are a rare subtype of BPNSTs that show characteristics of two or more types of BPNST. The most common combinations include:
- Schwannoma and perineuroma.
- Schwannoma and neurofibroma.
- Neurofibroma and perineuroma.
While these are the most commonly recognised hybrid tumours, they can occur in any combination. HPNSTs are more common in young adults, however they can develop at any age. These tumours are generally benign, and can have a good prognosis.
Treatment
When cancers are detected, they are staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you. However, as the PNSTs mentioned are considered benign, these tumours are generally considered low-grade and not staged.
Once your tumoura tissue mass that forms from groups of unhealthy cells has been diagnosed, your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, age, stage of disease and overall health.
Treatment options for BPNSTs may include:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence to remove as much of the tumour as possible.
- Watch and waitthe close monitoring of a cancer without giving treatment until symptoms appear or worsen.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
While the cause of BPNSTs remains unknown, the following factors may increase the likelihood of developing the disease:
- Being diagnosed with schwannomatosis (a rare type of neurofibromatosis).
- Being diagnosed with neurofibromatosis type 1 (NF1).
- Being diagnosed with neurofibromatosis type 2 (NF2).
- Being diagnosed with Carney complex.
Not everyone with these riskthe possibility that something bad will happen factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Symptoms
Many patients with BPNSTs may appear asymptomatic in the early stages of disease. As the tumour grows, symptoms may appear, and often vary based on location.
Some of these symptoms include:
- Pain in the affected area.
- Numbness and/or tingling in affected area.
- Itching and/or burning sensation in affected area.
- Weakness and/or loss of function in affected area.
- A massa growth of cells that come together to make a lump, may or may not be cancer that may be firm and/or palpable.
- Dizziness.
- Loss of balance.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have a BPNST, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Neurological examinationan assessment of sensory and motor functions, such as vision, balance and coordination.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- PET (positron emission tomography) scana type of medical imaging that uses radioactive tracers to create detailed images of the body.
- Ultrasounda type of medical imaging that uses soundwaves to create detailed images of the body .
- Blood teststesting done to measure the levels of certain substances in the blood.
- Electromyogram (EMG)a diagnostic procedure used to measure the response of nerves and skeletal muscles to electrical activity.
- Nerve conduction studiesa diagnostic procedure used to measure the speed of electrical impulses through a nerve.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
