Understanding Malignant Schwannoma: Symptoms, Diagnosis, and Treatment

What Is Schwannoma?

A schwannoma is a tumor that develops from Schwann cells in the peripheral nervous system, which is slow growing and benign in most cases but rare instances can turn malignant. The most common type of schwannoma is vestibular schwannoma, which affects the nerve in the inner ear that connects to the brain. The Schwann cells form the nerve cells' protective lining and help conduct the impulse. Therefore schwannomas, benign or malignant, interfere with and affect the normal functioning of the nerves. These tumors are found as a single mass, or solitary, and are also termed neurilemmomas or neuromas.

What Is Malignant Schwannoma?

Malignant schwannomas are rare tumors that develop from the Schwann cells; these tumors mainly affect the limbs' nerves, like the leg's sciatic nerve and the hand's brachial plexus nerve. Schwannoma, when it turns malignant, is termed soft tissue sarcoma. Malignant schwannomas have a higher frequency of occurrence in patients with neurofibromatosis type I or can occur spontaneously in adults.

What Are the Symptoms of Malignant Schwannoma?

Schwannomas are slow-growing tumors that can remain asymptomatic for years. As these tumors have a varied site of occurrence, symptoms, even when present, differ widely, ranging from mild to severe. Some of the common symptoms presented by malignant schwannomas are as follows:

• An observable lump or swelling which is tender on palpation.

• Numbness.

• Paresthesia.

• Muscle weakness.

• Sharp, burning pain.

The other symptoms of the schwannomas vary according to the site of the tumor-like:

• Vestibular schwannoma, which affects the nerves of the inner ear, affects the hearing and postural balance of the person.

• When it occurs in the facial nerve, schwannoma affects hearing, swallowing, facial expressions, and other functions related to the facial nerve.

• Schwannoma in the sciatic nerve at times behaves like disk herniation and presents with the symptoms like back pain and difficulty in walking and standing for long hours. The pain of the sciatic nerve radiates down the leg.

What Are the Causes of Malignant Schwannoma?

The exact cause of the malignant schwannoma is not known, but studies and cases have reported having an association with genetic disorders like neurofibromatosis and schwannomatosis. In addition, it has been reported that the gene on chromosome 22, an NF2 gene, has a great association and role in causing the disorder.

How Is Malignant Schwannoma Diagnosed?

Schwannoma is commonly an asymptomatic and a slow-growing benign tumor; therefore is present for a long duration, even for many years before it is diagnosed. These tumors are diagnosed accidentally during radiographic imaging for other conditions, or in symptomatic cases, the radiographic examination can be advised by the physician to rule out other possible conditions.

Some commonly performed radiographic test that helps in confirming the diagnosis include:

Magnetic Resonance Imaging: MRI is an imaging technique where all the organs and body structures are examined using a large magnet and radio waves to produce a clear structural image. This is one of the commonly used methods to detect and diagnose Schwannoma.

Computed Tomography: CT scan is also an imaging technique used for diagnosis, which uses X-Rays for imaging the internal structures.

Ultrasound: Itis an imaging technique that uses high-frequency sound waves to create real-time images or recordings of internal organs or other soft tissues. Ultrasound can be used to detect schwannomas under the skin.

Electromyogram (EMG): This test is performed by placing a small needle in the muscle to record the electric activity of the muscle on its movement.

Nerve Conduction Study: This test is done to assess the speed with which the electrical impulse is conducted by the muscles.

Tumor Biopsy: If imaging tests define a nerve tumor, a sample from the tumor is removed for further analysis by the physician. This is an invasive procedure; therefore, depending on the size and site of the tumor, the time and type of anesthesia to be administered are decided.

Nerve Biopsy: It is similar to a tumor biopsy, done when the lesion is found in or around the nerves.

Biopsy and other lab tests like blood examination or microscopic studies of the sample can help in confirming the diagnosis.

What Is the Differential Diagnosis of Malignant Schwannoma?

• Neurofibromas.

• Neurofibromatosis I.

These lesions are commonly confused with schwannomas and are differentiated by radiographic or imaging differences.

How Is Malignant Schwannoma Treated?

The treatment for schwannomas depends on the growth size and symptoms. Depending on the mentioned conditions, treatment can be as follows:

Monitoring: The condition is observed if it is growing fast or is stable for a long period before any invasive treatments are carried out. This phase of treatment includes regular follow-ups and imaging.

Surgery: The tumor is removed surgically when it is painful and metastases to adjacent or other sites. This surgery is performed by an experienced peripheral nerve surgeon under general anesthesia. The time taken for surgery and recovery depends on the size and location of the tumor. In addition, these tumors can recur even after the surgery.

Radiation Therapy: Radiation therapy is used as a combination of therapy and surgery, which can help control the tumor's growth.

Stereotactic Radiosurgery: This is a type of treatment performed when the tumor is near vital nerves or blood vessels; this technique is used to limit the damage and spread of the tumor, and radiation is delivered to the site precisely without making an incision.

Can Schwannomas Be Prevented?

As the schwannomas are caused due to unknown reasons, it is nearly impossible to prevent the occurrence of the tumor. In cases where the condition is genetic, parents must see a genetic counselor when planning to have a child.

What Is the Prognosis in Cases with Schwannoma?

Various factors that determine the prognosis of this tumor include:

• Site of the tumor.

• Amount of tumor excised during surgery.

• The prognosis is very good in cases where the tumor is completely excised.

• There are a few complications in treating patients with Schwannoma, which include:

• Size of the tumor: Large tumors are difficult to be treated.

• Location of the tumor: Tumors near vital organs or nerves cause complications.

• Origin: Tumor originating from the ulnar nerve.

Conclusion:

Malignant schwannomas are tumors of the soft tissues that originate from the Schwann cells. The exact etiology of the tumor is unknown and is asymptomatic in most cases; these tumors are diagnosed accidentally and are treated surgically or by radiation therapies.