What Is a Peripheral Nerve Sheath Tumor?
The peripheral nerve sheath is a layer of soft tissue that surrounds the nerves moving out of the brain and spinal cord. One is said to have a peripheral nerve sheath tumor (PNST) if the cells constituting the layer, i.e. the peripheral nerve sheath, are growing at an abnormal rate. Since the body is made up of nerves in every region, this tumor can develop anywhere, however, it is most common in major nerves especially those around the neck, arms, lower back, and legs. Most peripheral nerve sheath tumors are benign such as schwannomas and neurofibromas. Regardless, there are those that are malignant, i.e. the malignant peripheral nerve sheath tumor (MPNST), also known as neurofibrosarcoma or malignant schwannoma.
The Pathology Of Peripheral Nerve Sheath Tumors
Benign peripheral nerve sheath tumors, i.e. schwannomas and neurofibromas, are usually low-grade meaning they grow at a slow rate. In addition to that, they are not as life-threatening as malignant peripheral nerve sheath tumors and do not metastasize to other body areas. If they are not treated early enough, benign peripheral nerve sheath tumors can affect the functionality of nerves as they press against them. As a result, a patient which such a tumor may experience pain, numbness, and weakness in the affected peripheral nerve. MPNST is more aggressive and develops at a fast rate.
The etiology of peripheral nerve sheath tumors is unknown, however, they are related to inherited autosomal disorders. For example neurofibromatosis type 1 and type 2 which are caused by NF1 gene and NF2 gene respectively. In most incidences of malignant peripheral nerve sheath tumors, they are usually as a result of a mutation in the NF1 gene or presence of neurofibromatosis type 1 disorder. On the other hand, neurofibromatosis type 2 disorder often leads to schwannomas, especially in the spine and intracranial nerves. Peripheral nerve sheath tumors can also develop sporadically or develop as a result of past exposure to radiation.
Symptoms Of Peripheral Nerve Sheath Tumor
Symptoms of peripheral nerve sheath tumor will vary depending on which nerves have been affected and their location. During the onset of the tumor, patients will barely have any warning signs of the tumor. However, as the tumor starts to grow into a large mass and press against the affected nerves, symptoms will arise. Nonetheless, the size of the tumor does not always determine the development of symptoms. Some of the common symptoms of peripheral nerve sheath tumors include;
- A lump or swelling in the soft tissue under the skin
- The lump is usually growing in size and often larger than 5 centimeters
- Frequent pain and tingling sensation
- Weakness and loss of function related to the affected nerves
- Dizziness and loss of balance
Prognosis Of Peripheral Nerve Sheath Tumors
The prognosis of peripheral nerve sheath tumors is usually promising if detected and treated early enough. As for benign PNSTs, they have a good prognosis and will not reoccur after being surgically removed. On the other hand, MPNSTs have a poor prognosis as they continue to develop into large masses whilst they still remain undiagnosed. Peripheral nerve sheath tumors can be diagnosed via a physical examination to examine the lump under the skin, or a scan so as to get a clear image of the location and size of the tumor. A biopsy can also be done by examining a tissue sample from the lump/swelling to identify whether it is cancerous or not. The prognosis of PNST can also be determined by the rate at which the tumor is growing or the staging of the tumor. What matters most is whether the tumor can be treated or controlled, meaning the prognosis is promising, as opposed to the prognosis of a tumor which cannot be treated or controlled.
Peripheral nerve sheath tumors are a rare type of sarcomas which can affect any gender within the age bracket of 30-50 years. That, however, does not mean that children, teenagers, and older adults cannot develop such tumors. Peripheral nerve sheath tumors are treated with surgery, chemotherapy, and radiation. In a means of further understanding the tumor, a patient can be treated in a clinical trial. Whereby an investigation is conducted to weigh how the tumor will respond to new medical interventions.