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Plexiform Schwannoma

Last updated Dec. 17, 2018

Approved by: Krish Tangella MD, MBA, FCAP


Microscopic pathology image showing schwannoma tumor.

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

  • Non-Melanotic Plexiform Schwannoma
  • Plexiform Neurilemoma
  • Plexiform Neurolemoma

What is Plexiform 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
  • There are various histological types of schwannomas, which include:
    • Cellular Schwannoma
    • Plexiform Schwannoma
    • Microcystic (Reticular) Schwannoma
  • Plexiform Schwannoma is a subtype of schwannoma that affects children. It is called so, because the tumor has plexiform or multi-nodular growth pattern, when examined under a microscope by a pathologist. The pattern can either be conventional or cellular. Plexiform Schwannoma affects multiple nerves; it can also affect nerve plexus (group of nerves)
  • Currently, no causative factors have been identified for tumor formation. In case of multiple schwannoma (in a minority), the risk factors for the tumor include the presence of neurofibromatosis type 2 (NF2) and a positive family history
  • Plexiform Schwannomas are typically benign like conventional schwannomas. The tumors 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
  • 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 Plexiform Schwannoma is excellent. However, the prognosis may be influenced by factors that include the tumor location, the presence of NF2, and if any malignant transformations are noted

Who gets Plexiform Schwannoma? (Age and Sex Distribution)

  • Plexiform Schwannoma is usually diagnosed during childhood, some even at birth, due to its characteristic appearance. It can have a congenital presentation
  • Both males and females are equally affected
  • Schwannomas have no known geographical, racial, or ethnic preference; they are seen worldwide
  • Approximately 5% of all schwannomas are known to be Plexiform Schwannomas

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

Most Plexiform Schwannomas 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:

  • Trauma: It is often associated with Plexiform Schwannomas
  • 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. Nevertheless, this is a very rare occurrence
  • A family history of the tumor
  • Schwannomatosis: It is a genetic condition that is a usually seen in adults and manifests as multiple schwannomas. Plexiform Schwannomas are known to occur in a background of schwannomatosis
  • Gorlin-Koutlas syndrome: A complex genetic disorder of multiple tumors in the body including multiple schwannomas

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones 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 Plexiform Schwannoma? (Etiology)

  • The exact cause and mechanism of Plexiform 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

What are the Signs and Symptoms of Plexiform Schwannoma?

Plexiform 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 tumors with signs and symptoms, it may be dependent upon the location and type of the tumor.

  • Plexiform Schwannomas are solitary tumors (in a majority of the cases) that can occur anywhere in the body, around a nerve. The signs and symptoms depend upon the particular nerve that is affected
  • Most tumors are less than 2 cm (along the greater dimension) and appear as a firm mass
  • Frequent areas involved with schwannomas include the trunk, head and neck region, arms (upper extremities), followed by the legs (in some cases)
  • A majority of the tumors are located below the skin or found in the subcutaneous tissues. The tumor can affect the cutaneous nerve. Involvement of the cranial or spinal nerve is not noted
  • It has to be noted that schwannomas may or may not be attached to a nerve
  • Plexiform tumors are frequently found in association with other malignant brain tumors such as glioma and meningioma

How is Plexiform Schwannoma Diagnosed?

A diagnosis of Plexiform 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

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 Plexiform Schwannoma?

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

  • Compression of the underlying nerve, which can affect nerve function
  • The presence of other brain tumors can complicate the condition
  • 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); however, no metastasis has been documented

How is Plexiform Schwannoma Treated?

Treatment measures for Plexiform 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 Plexiform 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 is 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 Plexiform Schwannoma be Prevented?

Current medical research has not established a way of preventing Plexiform Schwannoma. 

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

  • The prognosis of Plexiform Schwannoma is excellent, if the tumor can be removed without damaging the underlying nerve. Most schwannomas are benign and do not recur when completely excised
  • In general, Plexiform Schwannomas are difficult to completely remove due to the fact that they may be closely involved with a nerve
  • The prognosis also depends upon the tumor site and 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

Additional and Relevant Useful Information for Plexiform Schwannoma:

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


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Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Aug. 27, 2016
Last updated: Dec. 17, 2018