Diagnosing and categorizing brain tumours

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Understanding the diagnosis of a brain tumour is necessary to choose the most effective treatment for your child. Find out about the different categories of brain tumours, staging and grading.

Key points

  • A primary brain tumour develops directly in the brain and the is most common type of brain tumour in children. A secondary brain tumour develops elsewhere in the body and spreads to the brain.
  • A benign tumour is not cancerous and grows slowly.
  • A malignant tumour is cancerous, grows quickly and can spread to other parts of the brain and spine (central nervous system). It is extremely rare that brain tumours spread to other parts of the body.

Diagnosis is an important stage in understanding what is happening with your child. To help make a diagnosis, your child's doctor will do a thorough neurological assessment and order some diagnostic tests. These tests can show whether a brain tumour is causing the symptoms your child has been experiencing. If there is a tumour, these tests will also provide information about the type of tumour and where the tumour is located. This information helps the treatment team choose the most effective treatment for your child.

What happens during diagnosis?

Diagnosis usually begins with a physical examination. This may be carried out by a neurologist, neurosurgeon, nurse practitioner, or medical resident. A family doctor, paediatrician, or an emergency room doctor may have already done a physical exam, but it is important for each new doctor to understand your child’s situation. The examiner will observe your child and ask questions about the symptoms as well as about your child’s past medical history. They will also conduct a neurological examination.

If the results suggest that there may be a brain tumour, additional tests will be scheduled. The next set of tests may involve brain scans or neuroimaging, which provides a picture of the brain. Your child's doctor may also decide to do electrophysiological tests to examine brain activity. For more information about all these diagnostic tests, please see the "Diagnosis of brain tumours” section on the Brain Tumours Learning Hub.

In most cases, the first doctor who will treat your child is a neurosurgeon. They will look at the results of the brain scans and physical examination and decide whether your child needs surgery.

Categorization of brain tumours

There are more than 100 different types of brain tumours in children. Tumours are usually named after the type of cell they develop from. For example, a glioma grows out of glial cells.

Tumours may also be described based on their location, such as a brainstem glioma. Sometimes the same tumour may have different names, which can be confusing. The name of a tumour can change as researchers learn more details about tumour cells.

You may also hear tumours being described in two other general ways:

  1. Where they begin to grow: primary and secondary tumours
  2. How fast they are growing: benign and malignant brain tumours. This may also be described as the grade of a tumour.

Primary and secondary brain tumours

A primary brain tumour develops directly in the brain. Most brain tumours in children are primary brain tumours.

A secondary tumour is rare in children. It develops first somewhere else in the body, such as in the bones or skin. When these abnormal bone or skin cells spread to the brain, they are called a "secondary" tumour.

Benign and malignant brain tumours

Benign brain tumours

A benign brain tumour is not cancerous. The cells in the tumour grow slowly. Many benign brain tumours can be removed by surgery and they do not grow back (recur). However, some benign brain tumours can be dangerous. This is because they are located in a part of the brain that is difficult to reach by surgery or in an important part of the brain that could be harmed by surgery.

Malignant brain tumours

A malignant brain tumour is considered cancerous. This means the abnormal cells in the tumour are making copies of themselves quickly. As a result, the tumour grows quickly, and tumour cells can spread to other parts of the brain or spine. This is called metastasis. However, in many cases, cancerous tumours can be successfully treated. They rarely spread outside the central nervous system (CNS).

Sometimes the distinction between benign and malignant is more complex. Some benign tumours can spread to other parts of the brain or spine. This may occur, for example, in the case of low-grade gliomas. This does not mean that the tumour has become malignant. The low-grade glioma that has spread can often be successfully treated with chemotherapy or (more recently) targeted therapy.

Sometimes a benign tumour can transform into a malignant tumour. Although more common in adults, this can happen in children, especially teenagers.

What is grading?

Grading is a system that indicates how aggressively tumour cells are growing. Grade 1 tumours are considered benign and they do not grow fast. Grade 4 tumours are malignant, or cancerous, and they grow very quickly. The grade of a tumour is used to plan treatment and predict the course of the disease.

A doctor called a pathologist studies the tumour cells under a microscope to give the tumour a grade. In addition, they will use modern techniques (e.g., sequencing, methylation) to identify molecular tumour markers. These results are also used to plan treatment.

What is staging?

Staging determines the type of treatment that is most effective. This depends on several factors such as the child’s age, the type of tumour and whether it has spread to other parts of the body.

To stage the tumour, the following diagnostic tools are used: computerized tomography (CT) scans, magnetic resonance imaging (MRI), lumbar puncture, and rarely, bone marrow studies.

Types of brain tumours

Tumour cell typeComments
GliomasMay be located anywhere within the major areas of the brain (cerebral hemispheres, cerebellum, brainstem) or spinal cord ranging from benign (e.g., pilocytic astrocytoma, grade 1) to malignant (e.g., diffuse midline glioma, H3K27 altered, grade 4).
MedulloblastomaThe most common malignant tumour in childhood, WHO grade 4, located in the cerebellum and fourth ventricle (a fluid-filled space in the brain). There are four molecular groups of medulloblastoma: WNT-activated, SHH-activated, group 3 and group 4.
EpendymomaThird most common brain tumour in childhood, can be located anywhere in the brain and spine. Classification of ependymoma will take location (supratentorial, post fossa, spinal), how the tumour looks under the microscope and how molecules interact with one another into consideration.
Myxopapillary ependymomaTypically located in the lower spine in teenagers or adolescents, WHO 1.
Germ cell tumours
GerminomaMost common type of germ cell tumours, located in the suprasellar (between the top of the pituitary gland and the bottom of the hypothalamus) or pineal area (located just behind the brain stem) or both, WHO grade 4.
Non-germinomatous germ cell tumoursThis is a group of different tumour types such as Yolk sac tumour, Choriocarcinoma, Embryonal Carcinoma or a combination of those different tumour types. Some of the tumour types secrete tumour marker (AFP, hCG) into the bloodstream and cerebrospinal fluid which will aid in diagnosis and prognosis.
TeratomaNon-germinoma, non-secreting tumours; may be benign (mature) or malignant (immature).
CraniopharyngiomaSlow-growing, benign tumour located in the region above the pituitary gland.
Other central nervous system tumours
Dysembryoplastic neuro-epithelial tumourBenign tumour located within the brain, often causes seizures
Choroid plexus tumoursLocated in a part of the brain called the choroid plexus, most often in the lateral ventricles
Associated with overproduction of cerebrospinal fluid (CSF)
MeningiomaRare tumour during childhood, located in external lining of brain or spinal cord, may be benign (WHO 1) or malignant (WHO 3)
Pituitary adenomaRare benign tumour of the pituitary gland
Atypical teratoid/rhabdoid tumour (ATRT)Rare, fast-growing malignant tumour found mostly in infants
SchwannomaBenign, slow-growing tumour of the peripheral nerves
Last updated: September 11th 2023