While this section provides the name of many different tumours the list is not exhaustive and some rare brain tumours may not be listed. More than 60% of childhood tumours are located in the back compartment of the brain which includes the cerebellum, the brainstem and the fourth ventricle. The remaining 30 – 40% occurs in one of the two cerebral hemispheres of the cerebrum or in the spinal cord.
The 2021 CNS WHO classification of tumour type continues to support the molecular biomarkers importance in providing both ancillary and defining diagnostic information but it also emphasizes the importance of integrated diagnoses and layered reports. (Louis D.N et al Neuro-Oncology 2021).
Astrocytoma (also called Glioma)
These tumours arise from star shaped neural glial cells called astrocytes. The World Health Organisation classifies these tumours from grade 1 through to grade 4. Grade 1 is given to the most benign tumours and grade 4 to the most malignant. Common sites in children include the cerebrum, the cerebellum and the brainstem. Low-grade astrocytoma’s are usually localized and grow slowly over a long period of time. High-grade tumours are much more aggressive and may require more intensive therapy.
In children, more than 80 percent of astrocytoma’s are low-grade; nearly 20 percent are high-grade (e.g. Glioblastoma, IDH-wildtype Multiforme).
Atypical Teratoid/Rhabdoid Tumour (ATRT)
This malignant embryonal tumour most commonly occurs in children under two years of age and accounts for approximately 2% of childhood brain tumours. Intensive treatment is required and the prognosis is poor. If the tumour is found in older children there is often a better outcome.
Brainstem Gliomas
The brainstem is located deep within the posterior part of the brain and it is here where control of our most basic functions such as breathing, heart rate and blood pressure occur. Approximately 10% to 15% of childhood brain tumours are brainstem gliomas. Their location may cause sudden dramatic symptoms such as double vision, difficulty swallowing, clumsiness and weakness. The peak age group is between five and ten years. Prognosis varies dramatically with location within the brainstem.
Those tumours localised in the midbrain/medulla have a better survival than diffuse pontine gliomas. Sometimes, because of their location, surgery is not a practical or safe option. With diffuse pontine gliomas, also known as diffuse midline gliomas, prognosis is universally poor and these tumours cannot be cured. Patients’ symptoms often improve during or after six weeks of irradiation but unfortunately problems usually recur after six to nine months, and progress rapidly.
Survival past 12 to 14 months is uncommon, and new approaches to treating these tumours are urgently required.
Choroid Plexus Tumour
The choroid plexus is involved in the production of CSF and tumours arising from this location may cause marked hydrocephalus. Two types of choroid plexus tumours include the choroid plexus papilloma or carcinoma.
The choroid plexus papilloma is slow growing and tends to occur in children less than two years of age. It usually presents with hydrocephalus. Complete surgical removal of the tumour is often curative and usually no further treatment is necessary.
The choroid plexus carcinoma is a rare tumour and aggressive in its biology and behaviour. Intensive treatment is required and the prognosis is often poor.
Craniopharyngioma
This slow growing tumour accounts for 5 -10% of childhood brain tumours and it usually occurs in children between five and ten years of age. Craniopharyngiomas result from the growth of cells that early in foetal development have failed to migrate to their usual area just inside the bottom of the skull. These tumours arise from cells along the pituitary stalk and may grow up and involve the hypothalamus, optic nerve pathways and the third ventricle.
At diagnosis children may have symptoms such as headache and vomiting, hormonal deficiencies (growth delay, thyroid deficiencies, delayed puberty), visual disturbances and weight gain due to hormonal disturbances.
Complete removal of this tumour is optimal if it is in a favourable location. However, often this cannot be safely done without causing severe problems from damage to the pituitary hormones, the visual structures or the hypothalamus. For this reason, often a less aggressive approach to surgery is pursued, with subsequent radiotherapy used to provide long term control. The outcome from a craniopharyngioma in the modern era is generally favourable, but they are often associated with significant visual and hormonal deficits, and long-term follow-up is required.
Ependymoma
This tumour accounts for up to 10% of childhood tumours and often occurs in younger children. Ependymomas arise from cells lining the passageways in the brain that produce and store the cerebrospinal fluid or CSF. The tumours are most often in the back of the brain in an area called the posterior fossa, but they can also occur in the cerebral hemispheres.
Very few ependymomas spread to other parts of the brain or to the spinal cord before they are diagnosed. Symptoms from these tumours often include headache nausea, vomiting, visual changes and balance problems.
Surgery is utilised to remove as much of the tumour as possible depending on the tumour location. The best survival rates are from those children who have had a complete removal of their tumour. Radiation oncologists are now using focal radiation techniques after surgery with encouraging longer- term results. Chemotherapy, and repeat photon radiation has also been added to recent studies.
Gangliogliomas
These rare and benign tumours are slow growing but may occur anywhere in the brain or spinal cord. They arise from ganglia type cells, which are a group of nerve cells. The tumour represents about 4% of all childhood brain tumours.
Surgery is the major form of treatment if the location allows for complete removal. Radiotherapy or chemotherapy may be considered if this is not achieved. The prognosis from these tumours is usually good.
Germ Cell Tumours
Germ Cell tumours may arise anywhere in the body however these tumours that arise from the germ cells in the brain, are most commonly found in the pineal or suprasellar region above the pituitary gland. Symptoms can include hydrocephalus headache and nausea. The optic pathways may also be involved and result in double vision. Germ cells also have the ability to spread to other parts of the brain. This tumour represents about 4% of all childhood brain tumours.
Germinomas are the most common of all germ cell tumours and have a peak incidence around ten to twelve years of age with boys being affected more than girls. These tumours respond favourably to radiation therapy and chemotherapy following surgery.
Non-Germinatous Germ Cell Tumours contain a mixture of malignant cells that secrete hormones. Treatment is similar and recent studies have shown marked improvement in outcome although data available is limited.
Germ cell tumours often produce hormone chemicals that can be measured in the blood or CSF, and initial surgery is not required to establish the diagnosis. Surgery may be required later however if chemotherapy or radiotherapy does not result in complete resolution of the tumour.
Medulloblastomas
These are the most common malignant childhood brain tumour in childhood. They most often occur in the first decade of life; half occur in children younger than five to six years of age.
These tumours tend to arise in the middle of the cerebellum, interfering with CSF flow and resulting in hydrocephalus. These tumours are diagnosed by an integrated molecular and phenotypic basis that provides 4 different groups with differing outcome. This tumour type has a tendency to spread to other areas of the brain and spinal cord.
Treatment is with initial neurosurgery, aiming for complete resection. This is followed by central nervous system radiation therapy and chemotherapy. The outcome of this treatment is dependent on the biology of the tumour (identified by biological and genetic markers in the tumour specimen) but overall is considered to be favourable.
Optic Pathway Gliomas (Nerve Sheath Tumours)
This is a low grade tumour which grows along the optic nerve, optic chiasm and the hypothalamus. It is often a pilocytic astrocytoma and is called an optic pathway glioma because of its location. This tumour represents about 5% of all childhood brain tumours. 50% -70% of these children have an association with a genetic condition called neurofibromatosis Type 1. This is an inherited disorder of the nervous system causing tumours to grow on nerves.
Signs and symptoms depend on the specific location of the tumour and the age of the patient. Decreased vision and double vision may be present. Infants may display head bobbing, head tilt, and nystagmus (oscillation of the eyeballs.) Growth and endocrine disturbances can also be symptoms of optic pathway tumours including changes in sleep and appetite.
Treatment strategies include surgery, chemotherapy and radiotherapy. The location of the tumour, the age of the child and the amount of visual loss will impact on the plan. Outcome of treatment is considered to be favourable.
Clinical trials
New treatment strategies for tumours of the central nervous system are being developed all of the time. Often these involve changes to the cocktail of chemotherapy drugs used to treat a particular tumour type, or different timing or combination of various treatment modalities (e.g. giving altered doses of radiotherapy together with chemotherapy).
When these treatment changes are introduced, it is not known whether or not they will provide additional benefit, or even potentially cause more side-effects to the children. For this reason they are usually introduced on the basis of a clinical trial, where the outcome data are carefully documented, collected and reviewed over time to see whether additional benefit is provided. You should discuss new clinical trials and the thinking behind them with your treating oncologist.
If your child is enrolled in a clinical trial, it is important to realise that it does not necessarily mean that doctors know that the treatment offered is better, but it is always the hope that it will be.
