Ganglioglioma

Overview

Ganglioglioma is a rare tumor that grows in the brain or spinal cord. It's made up of two types of cells found in the nervous system — glial cells and nerve cells. Ganglioglioma is classified as a glioneuronal tumor.

Most gangliogliomas are low grade. That means they are considered noncancerous (benign) and are not aggressive cancers. They grow slowly, are less likely to spread and often can be fully removed with surgery.

When the tumor is completely removed, many people live for many years and may have a typical life expectancy.

Less often, gangliogliomas may have aggressive or high-grade features. These were previously called anaplastic gangliogliomas, which we now know may include different tumor types. That means they grow more quickly and require more intensive treatment. However, high-grade forms are much less common than low-grade tumors.

Gangliogliomas most often occur in the temporal lobe of the brain. This area of the brain is a common site of seizures. Seizures are one of the most common reasons these tumors are discovered. Less often, gangliogliomas can develop in other parts of the brain or in the spinal cord.

This tumor is seen most often in children, adolescents and young adults, although it can occur at any age. Ganglioglioma accounts for a small percentage of all brain tumors.

Types

Gangliogliomas are grouped by features seen under the microscope and other genetic characteristics. Gangliogliomas are classified by the World Health Organization as low grade (WHO grade 1).

• Ganglioglioma (WHO grade 1). This is the most common type of ganglioglioma.

  Low-grade tumors grow slowly. They usually stay in one area of the brain or spinal cord. In many cases, surgery can remove the tumor completely. When that happens, long-term survival rates are high.

  Gangliogliomas are often linked to seizures, especially when the tumors grow in the temporal lobe of the brain.

  Very rarely gangliogliomas can develop high-grade or aggressive features, which is most often at time of progression or recurrence. High-grade tumors grow more quickly and are more likely to return after treatment. They often require additional treatment beyond surgery, such as radiation therapy or chemotherapy.

• Desmoplastic infantile ganglioglioma (DIG). Desmoplastic infantile ganglioglioma is a rare type that mainly affects infants and very young children.

  Desmoplastic infantile gangliogliomas most often occur in the cerebral hemispheres. Rarely, they have been reported in other areas of the brain. This includes the posterior cranial fossa, which contains the cerebellum.

  These tumors can be large at the time they are found. Even so, they are usually low-grade, slow-growing tumors. With surgery, many children have good outcomes.

Is anaplastic ganglioglioma still a grade 3 tumor?

Before 2021, some tumors were called anaplastic ganglioglioma and labeled WHO grade 3. Doctors made this diagnosis mostly by looking at the tumor under a microscope. If the tumor looked like a ganglioglioma but also showed more-aggressive features, it was called anaplastic, which meant higher grade.

At the time, experts believed these tumors were all the same type — just a more aggressive form of ganglioglioma.

What changed?

As genetic testing improved, researchers began studying these tumors more closely. This testing, called molecular testing, looks at the tumor's genes. When experts tested tumors that had been labeled anaplastic ganglioglioma, they found that most of them did not share the same genetic features.

Instead, many of these tumors matched the genetic patterns of other known tumor types, including:

• Pleomorphic xanthoastrocytoma (PXA).
• Glioblastoma, IDH-wildtype.
• Diffuse pediatric-type high-grade glioma.
• IDH-mutant astrocytoma.
• Other glioneuronal tumors.

This meant that what had been grouped together as one diagnosis was actually a mix of different tumor types that only looked alike under the microscope.

What does this mean?

Today, tumors are classified using information about how they look under a microscope and their genetic and molecular features.

Gangliogliomas are usually described in one of two ways:

• Central nervous system (CNS) WHO grade 1 (low-grade).
• Higher grade tumors that fit into other WHO-defined categories.

Because these tumors turned out to be biologically different diseases, the 2021 World Health Organization (WHO) Classification of Tumors of the Central Nervous System removed anaplastic ganglioglioma as an official diagnosis. There is no longer a recognized WHO grade 3 ganglioglioma category.

Pilocytic features

Some people may see the words pilocytic features in their pathology reports. A pathology report is the written summary a specialist creates after studying the tumor under a microscope.

Pilocytic features means that some parts of the tumor look similar to a tumor called pilocytic astrocytoma. It describes how the cells appear under the microscope. It does not mean the tumor is a different condition. Pilocytic astrocytoma and ganglioglioma are different tumor types, even though they can look similar in some ways.

Symptoms

Symptoms of ganglioglioma depend on where the tumor is located in the brain or spinal cord. Common signs and symptoms include:

• Seizures. Seizures are the most common symptom, especially when the tumor is in the temporal lobe. For some people, seizures may have been happening for months or even years before the tumor is found.
• Headaches. Headaches can occur, especially if the tumor causes pressure inside the skull. Headaches may be more frequent in the morning or linked to nausea.
• Changes in thinking or behavior. If the tumor affects areas of the brain involved in memory, speech or mood, it may cause memory problems, trouble speaking, or changes in personality or behavior.
• Weakness or balance problems. Tumors in certain parts of the brain may cause weakness on one side of the body, balance problems or trouble with coordination. If the tumor is in the spinal cord, it may cause weakness, numbness or difficulty walking.
• Symptoms in infants and young children. In infants, symptoms may look different. Signs can include an enlarged head size, vomiting, irritability or delays in development.

When to seek care

You should contact a healthcare professional if you or your child has:

• New or unexplained seizures.
• Seizures that are becoming more frequent.
• Ongoing headaches that are getting worse.
• Changes in behavior, memory or speech.
• Weakness, numbness or balance problems.

These symptoms do not always mean there is a tumor. Many other conditions can cause similar symptoms. However, ongoing or worsening symptoms should be checked by a healthcare professional.

Causes

The exact cause of ganglioglioma is often unknown.

Most gangliogliomas develop because of changes in certain genes that control how cells grow and divide. These changes only happen inside the tumor cells. They are not usually passed down in families.

Many gangliogliomas have changes that affect a cell growth pathway called the RAS-MAPK pathway. Changes in a gene called BRAF are common. These genetic changes help explain how the tumor forms, but they do not usually mean the condition is inherited.

In most people, ganglioglioma is not caused by anything a parent did or did not do. It is not linked to diet, lifestyle or routine activities.

Rarely, brain tumors can occur in people with certain genetic conditions, but ganglioglioma is usually not related to a genetic condition.

Risk factors

There are no known risk factors for ganglioglioma.

Ganglioglioma is most often diagnosed in children, teens and young adults. It's less common in adults.

Most people who develop this tumor do not have any known medical condition that raises their risk.

Prevention

There is no known way to prevent ganglioglioma.

Ganglioglioma usually develops without a known trigger. Because of this, there are no screening tests or preventive steps recommended for the general population.