Schwannoma

Schwannoma

Article
Ear, Nose, & Throat (ENT)
Brain & Nerve
+4
Contributed byKrish Tangella MD, MBADec 19, 2018

What are the other Names for this Condition? (Also known as/Synonyms)

  • Neurilemoma
  • Neurolemoma
  • Schwann Cell Tumor

What is Schwannoma? (Definition/Background Information)

  • Schwannomas are a group of tumors that arise from the Schwann cells around the nerves; these tumors are essentially nerve sheath tumors. They are commonly seen in young, middle-aged, and slightly older adults
  • It is very important to note that a Schwannoma is not a premalignant condition to a tumor called malignant peripheral nerve sheath tumor (MPNST); in other words, MPNST does not arise from a Schwannoma
  • Based upon the clinical behavior, genetic mutations, and tissue biopsy studies, Schwannomas can be subdivided into the following types:
    • Benign Conventional Schwannoma: Conventional Schwannomas are typically benign; though rarely, they can become malignant
    • Melanotic Schwannoma: A tumor of low malignancy potential
  • There are various histological types of Schwannomas, which include:
    • Cellular Schwannoma: This is a type of Schwannoma which has characteristic features, when examined under a microscope by a pathologist
    • Plexiform Schwannoma: This type of Schwannoma affects multiple nerves; it can also affect the nerve plexus (group of nerves). Only a minority of individual with this type are known to have a history of neurofibromatosis type 2 (NF2)
    • Microcystic (Reticular) Schwannoma: It is a very uncommon type of Schwannoma having a characteristic microscopic appearance
  • Currently, no causative factors have been identified for tumor formation. In case of the presence of multiple Schwannomas (in a minority of cases), the risk factors for the tumor include the presence of NF2 and a positive family history of Schwannoma
  • Schwannomas may be asymptomatic (in many cases) or symptomatic. The signs and symptoms are commonly based upon the location of the tumor and can be wide-ranging. Vestibular Schwannomas can cause hearing loss and ringing within the ears; peripheral Schwannomas that are present in the arms and legs may be present as a mass without any significant symptoms
  • In rare cases, Schwannomas are known to develop into malignant tumors. The tumors can also compress the nerve on which it lies and cause nerve dysfunction
  • In a majority of cases, a complete excision by surgery can be curative and the prognosis of Schwannoma is excellent. However, the prognosis may be influenced by factors that include the type of Schwannoma, tumor location, the presence of NF2, and if any malignant transformations are noted

Who gets Schwannoma? (Age and Sex Distribution)

  • Schwannoma is typically observed between the age ranges of 30-60 years. It is generally observed in young, middle-aged, and slightly older adults
    • Plexiform Schwannoma is usually diagnosed during childhood, some even at birth, due to its characteristic appearance
    • Microcystic (Reticular) Schwannoma is extremely rare and fewer than 10 cases have been reported
  • Schwannomas occurring in the background of neurofibromatosis type 2 (NF2) are seen before age 30 years; they usually occur earlier in life. However, against a background of NF2, the tumors may be observed with a higher incidence in females than males
  • Both males and females are equally affected
  • Schwannomas have no known geographical, racial, or ethnic preference; they are seen worldwide

What are the Risk Factors for Schwannoma? (Predisposing Factors)

9 in 10 cases of Schwannoma are solitary in nature with generally no identifiable risk factors. On the remaining cases, there may be the presence of multiple tumors in the body. The risk factors for multiple Schwannomas may include:

  • The presence of neurofibromatosis type 2 (NF2), a genetic condition that is characterized by the formation of non-cancerous tumors that affect the nervous system. Approximately 4% of the Schwannomas are associated with NF2
  • A family history of the tumor
  • Schwannomatosis: It is a genetic condition that is a usually seen in adults and manifests as multiple Schwannomas. Schwannomatosis is a type of neurofibromatosis, and it does not generally involve the vestibular nerve, unlike some Schwannoma
  • Gorlin-Koutlas syndrome: A complex genetic disorder of multiple tumors in the body including multiple Schwannomas
  • Trauma: It is often associated with Plexiform Schwannomas

Note: 5% of Schwannoma cases involve multiple tumors, even though an association with or a history of NF2 is not present.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Schwannoma? (Etiology)

  • The exact cause and mechanism of Schwannoma formation, in a majority of cases, is unknown; they are known to be the result of sporadic mutations. This implies that they do not have a preceding family history of the condition
  • Abnormalities in chromosome 22 is the most common finding; trisomy 17 is observed in recurrent Plexiform Cellular Schwannoma
  • Multiple Schwannomas are known to occur in a background of genetic disorders, such as neurofibromatosis type 2 (NF2), Gorlin-Koutlas syndrome, or a positive family history
  • In general, the tumor is believed to be caused by the overproduction of Schwann cells that wrap around the nerve

Note: Schwannomas in NF2 have a strong family history of the condition; whereas, in contrast, only 1 in 6 Schwannomatosis cases (15%) are known to have a family history.

What are the Signs and Symptoms of Schwannoma?

Schwannomas are slow-growing tumors and a majority does not exhibit any significant signs and symptoms. They are typically detected incidentally, when the individual is being examined for some other medical condition. In Schwannomas with signs and symptoms, it may be dependent upon the location and type of the tumor.

  • Schwannomas are solitary tumors (in 90% cases) that can occur anywhere in the body, around a nerve (on the nerves of the spine or peripheral nerves of the arms and legs)
  • They may range in size from 2-10 cm (along the greater dimension) and appear as a firm mass
  • Frequent areas involved include the skin, head and neck subcutaneous tissues, arms and legs; followed by the intracranial nerves (that occur inside the cranium/head)
  • Schwannoma can affect the cranial nerve and cutaneous nerve. It has to be noted that Schwannomas may or may not be attached to a nerve
  • The most common cranial nerve involved is the CN VIII, or the vestibular nerve, resulting in Vestibular Schwannoma. Due to this, individuals may have ear-related signs and symptoms including dizziness/vertigo, hearing loss, tinnitus (ringing in the ears), or altered touch sensation on the face
  • When the tumor involves the spinal nerve, it is called Spinal Schwannoma; rarely, GI tract and bones are involved, in which case, these are known as Gastrointestinal Schwannoma and Osseous Schwannoma respectively
  • Spinal Schwannoma can present pain; the pain can be localized depending on the level/region of spinal cord involved. Spinal Schwannomas are mostly observed in the cervical and lumbar region and may cause associated signs and symptoms
    • Cervical Spinal Schwannoma may result in neck pain
    • Thoracic Spinal Schwannoma may present pain in the arms and back
    • Lumbar Spinal Schwannoma may show pain in the lower back and legs
  • Cellular Schwannoma:
    • Usual locations are along the vertebral column/spinal cord (paravertebral Cellular Schwannoma), retroperitoneum (retroperitoneal Cellular Schwannoma), mediastinum (mediastinal Cellular Schwannoma), and pelvis (pelvic Cellular Schwannoma)
    • It may also involve the 5th cranial nerve (facial nerve), called facial nerve Cellular Schwannoma
    • It can affect the 8th cranial nerve, also called vestibular nerve Cellular Schwannoma
    • If the tumor is present near a bone, it can invade into the surrounding bone causing significant bone damage
  • Plexiform tumors are frequently found in association with other malignant brain tumors such as glioma and meningioma
  • In case the facial nerve is affected, it can cause swallowing difficulties, altered taste function, and abnormal eye movement
  • Schwannoma may be present as an asymptomatic mass on the arms (commonly on the brachial plexus nerve) or legs (on the sciatic nerve mostly)

How is Schwannoma Diagnosed?

A diagnosis of Schwannoma is made using the following tools:

  • Complete physical examination with thorough evaluation of the individual’s medical history (including family history of neurofibromatosis type 2 or Schwannoma)
  • Neurological exam of the entire body
  • Radiological studies (CT, MRI scan) of the affected region
  • Nerve conduction studies of the affected nerve
  • Other specific tests may be conducted based on the location of the tumor
  • Tissue biopsy: A tissue biopsy is performed and sent to a laboratory for a pathological examination, who examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis

Note:

  • Schwannomas, when examined under the microscope, have certain characteristic features. They also usually have a capsule around them. However, those arising in the brain, gastrointestinal tract (GI Schwannoma), bone (osseous Schwannoma), and underneath the skin (cutaneous Schwannoma), do not have a capsule around them
  • Cellular Schwannoma: Usually, Schwannoma has Antoni A areas and Antoni B areas admixed with Verocay bodies. In Cellular Schwannoma, there is an absence or very little of Antoni B areas; there is also an absence or decrease of Verocay bodies

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Schwannoma?

The complications can depend on where the tumors are located. The complications from Schwannoma could include:

  • Compression of the underlying nerve, which can affect nerve function
  • Damage to the nerve during surgery to remove the tumor. Sometimes, removing the tumor can worsen the signs and symptoms in some individuals
  • Infrequently, recurrence of the tumor after surgery, if the tumor is incompletely removed
  • Very rarely, Schwannomas can become malignant (malignant transformation of Schwannoma); 1% of tumors are observed to become cancerous
  • In rare instances, angiosarcoma (malignant tumor of the blood vessels) is known to arise from a Schwannoma

How is Schwannoma Treated?

Treatment measures for Schwannoma may depend upon the type and location of the tumor. In many cases, if the tumor is small-sized and there are no symptoms, no treatment may be necessary. Periodic observations can be maintained through regular check-ups.

Surgical excision and tumor removal is the usual mode of treatment of Schwannoma. A very important criterion for surgery is to preserve nerve function that is affected by the tumor. Surgical treatment options may include the following:

  • Microsurgery: The surgery is performed using microsurgical techniques, which can help minimize damage to the accompanying nerve. Since the tumor mostly affects the covering around the nerves, it can be completely removed without affecting the nerve in most cases. The following techniques may be employed:
    • Subtotal removal; when the tumor is incompletely removed
    • Near total removal; when most of the tumor is removed and there are very little tumor remnants
    • Total tumor removal; when the tumor is removed completely
  • Craniotomy: It is a surgical procedure wherein a tiny hole is created in the cranium to remove the tumor
  • Stereotactic radiosurgery is a relatively new treatment method that can be helpful in some individuals. It is a radiation therapy technique and not an invasive surgical procedure. It can be administered using a Gamma Knife (Gamma Knife radiosurgery)
  • Laminectomy: Surgical removal of the tumor can be attempted through a decompressive laminectomy for spinal Schwannomas. This intervention tool can help relieve pressure and compression caused by the tumor on the spinal cord. It is only performed when severe symptoms are noted

In case of malignancy, additional treatment options, such as chemotherapy and/or radiation therapy, may be considered.

  • Chemotherapy may be used to destroy the tumor cells
  • Radiation therapy may be useful in individuals who are not candidates for surgery. Such cases include:
    • Individuals with overall poor health status
    • Individuals with minimal symptoms
  • Treatment of the underlying neurofibromatosis type 2, if present
  • Post-operative care is important: One must maintain minimum activity levels, until the surgical wound heals
  • Follow-up care with regular screening and check-ups are important and encouraged

How can Schwannoma be Prevented?

Current medical research has not established a way of preventing Schwannoma. However, in case it is associated with genetic disorders, such as neurofibromatosis type 2, then the following may be considered:

  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks before planning for a child
  • Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as neurofibromatosis type 2
  • Regular medical screening at periodic intervals with tests and physical examinations are strongly recommended

What is the Prognosis of Schwannoma? (Outcomes/Resolutions)

  • The prognosis of Schwannoma (benign tumor) is excellent, if the tumor can be removed without damaging the underlying nerve. Most Schwannomas are benign and do not recur when completely excised
  • However, this also depends upon the subtype of the tumor, the tumor site, and the presence of neurofibromatosis type 2. If benign Schwannomas transform to malignant Schwannomas (in very rare occasions), then the prognosis may depend upon a set of several factors including the stage of the tumor, its location, overall health of the individual, and response to therapy
  • Asymptomatic tumors may require no treatment; unless they cause discomfort, affect the quality of life, or affect functioning of the underlying nerve. In such cases, close monitoring of the Schwannoma is a treatment option
  • Plexiform Schwannoma and Cellular Schwannoma are difficult to completely remove due to the fact that they may be closely involved with a nerve

Additional and Relevant Useful Information for Schwannoma:

A differential diagnosis may have to be undertaken to eliminate other tumors such as:

  • Neurofibroma
  • Leiomyosarcoma
  • Gastrointestinal stromal tumor (GIST)
  • Malignant peripheral nerve sheath tumor (MPNST)

Please visit our Cancer & Benign Tumor Health Center for more physician-approved health information:

http://www.dovemed.com/diseases-conditions/cancer/

Was this article helpful

On the Article

Krish Tangella MD, MBA picture
Approved by

Krish Tangella MD, MBA

Pathology, Medical Editorial Board, DoveMed Team

0 Comments

Please log in to post a comment.

Related Articles

Test Your Knowledge

Asked by users

Related Centers

Loading

Related Specialties

Loading card

Related Physicians

Related Procedures

Related Resources

Join DoveHubs

and connect with fellow professionals

Related Directories

Who we are

At DoveMed, our utmost priority is your well-being. We are an online medical resource dedicated to providing you with accurate and up-to-date information on a wide range of medical topics. But we're more than just an information hub - we genuinely care about your health journey. That's why we offer a variety of products tailored for both healthcare consumers and professionals, because we believe in empowering everyone involved in the care process.
Our mission is to create a user-friendly healthcare technology portal that helps you make better decisions about your overall health and well-being. We understand that navigating the complexities of healthcare can be overwhelming, so we strive to be a reliable and compassionate companion on your path to wellness.
As an impartial and trusted online resource, we connect healthcare seekers, physicians, and hospitals in a marketplace that promotes a higher quality, easy-to-use healthcare experience. You can trust that our content is unbiased and impartial, as it is trusted by physicians, researchers, and university professors around the globe. Importantly, we are not influenced or owned by any pharmaceutical, medical, or media companies. At DoveMed, we are a group of passionate individuals who deeply care about improving health and wellness for people everywhere. Your well-being is at the heart of everything we do.

© 2023 DoveMed. All rights reserved. It is not the intention of DoveMed to provide specific medical advice. DoveMed urges its users to consult a qualified healthcare professional for diagnosis and answers to their personal medical questions. Always call 911 (or your local emergency number) if you have a medical emergency!