Paediatric-type diffuse high-grade glioma (PDHGG)    

What are paediatric-type diffuse high-grade gliomas?

Paediatric-type diffuse high-grade gliomas (PDHGG) are a group of rare and aggressive brain tumours that mainly affect children and young people.

They are all types of glioma, which means they develop from glial cells – the supportive cells that help the brain and nervous system function.

These tumours are described as diffuse, meaning the cancer cells spread into surrounding brain tissue rather than forming a single, clearly defined lump. This makes them very difficult to remove completely with surgery.

They are also high-grade (grade 4), which means they grow quickly and are more aggressive. Because of this, PDHGGs are particularly challenging to treat and outcomes remain poor.

This is why research is so vital. Brain Tumour Research is funding scientists across the UK to better understand these tumours and develop kinder, more effective treatments for children and young people.

Brain Tumour Research has invested more than £2.7 million in research into paediatric high-grade gliomas since 2021. Read more about what we are doing to find a cure for these devastating childhood tumours here.

What are the symptoms of a brain tumour in children? 

The symptoms a child experiences often depend on where the tumour is in the brain. They can also differ based on the child’s age and stage of development. Symptoms can include:

  • Persistent headaches 

  • Nausea or vomiting 

  • Seizures 

  • Vision or eye problems 

  • Difficulty with strength, balance or coordination 

  • Noticeable changes in behaviour 

  • Issues with posture 

  • Delayed or halted puberty 

  • An unusually large head size in a baby 

Cancer in children is rare, and these symptoms are often caused by other conditions. However, it’s important to have your child checked by their GP.

How are PDHGGs diagnosed?   

Doctors use a combination of scans and tests to diagnose PDHGGs and to understand exactly which type of tumour a child has.

Brain scans

An MRI scan of the brain and spinal cord is usually the first step. MRI scans create detailed images of the brain, helping doctors identify abnormal areas.

Scans may be repeated over time to see whether a tumour is growing or changing.

Biopsy (tissue sample) 

In most cases, doctors take a very small sample of the tumour, known as a biopsy. This sample is examined under a microscope and tested for specific genetic changes. These tests help confirm the diagnosis, give doctors a better idea of how the tumour may behave and help guide treatment decisions.

What are the different types of PDHGG? 

There are four main types of PDHGG. Each type behaves differently and may respond differently to treatment. Researchers are continuing to study these tumours to better understand the smaller subtypes within each group.

  • Diffuse midline glioma H3 K27-altered

    Diffuse midline gliomas develop in the central parts of the brain, such as the brainstem, thalamus or spinal cord. They are most often diagnosed in young children and are commonly found in the pons, a vital part of the brainstem. These tumours were previously known as diffuse intrinsic pontine glioma (DIPG).

    Because of where they grow, most diffuse midline gliomas cannot be removed safely with surgery. Treatment usually involves radiotherapy and sometimes chemotherapy.

    Despite decades of research, outcomes remain very poor, which is why this area is a major focus of research into childhood brain tumours.

  • Diffuse hemispheric glioma H3 G34-mutant 

    Diffuse hemispheric gliomas are rare tumours that mainly affect teenagers and young adults. They develop in the cerebral hemispheres – the large areas of the brain responsible for movement, speech, memory and thinking.


    These tumours are linked to specific genetic changes that help doctors identify them. Treatment usually involves surgery where possible, followed by radiotherapy and chemotherapy.

  • Diffuse paediatric-type high-grade glioma  H3-wildtype and IDH-wildtype 

    This type of tumour also usually develops in the cerebral hemispheres. It is described as H3-wildtype and IDH-wildtype as, unlike some other gliomas, it does not have certain genetic changes.

    Treatment typically involves surgery followed by radiotherapy and chemotherapy. There are several different subtypes within this group, which means outcomes can vary.

  • Infant-type hemispheric glioma 

    Infant-type hemispheric gliomas occur in babies under 12 months old and develop in the cerebral hemispheres. They have different genetic changes from other high-grade gliomas.


    Although these tumours are aggressive, many infant-type hemispheric gliomas have a better outlook than other PDHGGs.

What are the treatments for PDHGG? 

  • Surgery

    Where possible, surgeons aim to remove as much of the tumour as is safe. Some tumours grow in areas of the brain that cannot be operated on safely, in which case only a biopsy may be carried out.

    Find out more 

  • Radiotherapy

    Radiotherapy uses high-energy beams to damage tumour cells and stop them from growing. It is often given after surgery or as the main treatment when surgery is not possible.


    In some centres, proton therapy may be offered. Proton therapy is a type of radiotherapy that can be even more precise, which may help reduce long-term side effects, especially in children.

    Find out more 

  • Chemotherapy

    Chemotherapy uses medicines to slow or stop tumour growth. It may be given alongside radiotherapy or surgery. In very young children, chemotherapy is sometimes used to delay radiotherapy to help protect the developing brain.

  • Targeted Therapy

    Targeted therapies are treatments designed to block specific molecules that help cancer cells grow and survive. By focusing on these particular pathways, they aim to slow down or stop the tumour while causing less harm to healthy cells.

    There are currently no targeted therapies for paediatric high-grade gliomas, however read more here about an approved treatment for low-grade gliomas with a BRAF V600E mutation.

  • Immunotherapy

    Immunotherapy is a type of treatment that helps the body’s own immune system recognise and attack cancer cells. It’s a fast‑moving area of research, and early studies suggest it may hold promise for treating some brain tumours in the future.

    However, immunotherapy is not yet a standard treatment for paediatric high-grade gliomas. More research and clinical trials are needed to understand which approaches work best and how they can be used safely in children.

  • Clinical Trials

    Families may be offered the opportunity to take part in clinical trials, which test new treatments or combinations of treatments. Clinical trials are essential for improving outcomes for children diagnosed in the future.

    Discover how we’re funding research to move new treatments towards clinical trials for children.

    Find out more 

  • Supportive Care

    Alongside treatment, children and families receive support to help manage symptoms and cope with the emotional impact of a brain tumour diagnosis. Regular follow-up appointments and scans help doctors monitor recovery and identify any changes as early as possible.

Frequently Asked Questions

Are paediatric gliomas different to adult gliomas?  

Yes. In the past, childhood gliomas were often grouped together with adult gliomas or described using older terms, such as paediatric glioblastoma or diffuse intrinsic pontine glioma, known as DIPG.

Research has since shown that paediatric gliomas are biologically different from adult gliomas. This means they can have different genetic and molecular features and may behave differently. Because of this, the World Health Organization now classifies paediatric gliomas separately from adult gliomas.

In the 2021 World Health Organization classification of central nervous system tumours, paediatric gliomas are divided into two broad groups:

Paediatric-type diffuse low-grade gliomas, grades 1 to 2
These include tumour types such as pilocytic astrocytoma, ganglioglioma and other low-grade gliomas with specific genetic changes.

Paediatric-type diffuse high-grade gliomas, grades 3 to 4
This group includes diffuse midline glioma, H3 K27-altered; diffuse hemispheric glioma, H3 G34-mutant; diffuse paediatric-type high-grade glioma, H3-wild type and IDH-wild type; and infant-type hemispheric glioma.

Understanding these differences is important because it helps researchers develop treatments that are designed around the biology of childhood brain tumours, rather than relying on approaches developed for adult disease.

What happened to the diagnosis of paediatric glioblastoma? 

Under the latest World Health Organization (WHO) classification of brain tumours, introduced in 2021, paediatric glioblastoma is no longer recognised as a separate diagnosis.

Previously, a child whose tumour looked like a glioblastoma under the microscope would often be diagnosed with paediatric glioblastoma or glioblastoma (WHO grade 4). Today, doctors also carry out molecular and genetic testing to understand the tumour's underlying biology. This means tumours are classified not just by how they look, but by the genetic changes that drive them.

As a result, many tumours that would once have been called paediatric glioblastoma are now diagnosed as one of several paediatric-type diffuse high-grade gliomas (PDHGGs), including:

- Diffuse midline glioma, H3 K27-altered

- Diffuse hemispheric glioma, H3 G34-mutant

- Diffuse paediatric-type high-grade glioma, H3-wildtype and IDH-wildtype

- Infant-type hemispheric glioma

This change reflects research showing that childhood high-grade gliomas are biologically different from adult glioblastoma and may respond differently to treatment. More precise diagnoses help doctors better predict prognosis, identify potential targeted treatments and match children to the most appropriate clinical trials.

Although rare, some children can still be diagnosed with an adult-type glioblastoma. In these cases, molecular testing shows the tumour has the genetic characteristics of an adult-type glioblastoma rather than a paediatric-type tumour. The diagnosis is therefore based on the tumour's biology, not simply the child's age.

Can adults develop PDHGGs? 

Yes, but this is very rare. When this happens, the tumour is still described as paediatric-type because of its biology, not the person’s age.

What are brainstem gliomas?

Brainstem glioma is a broad term. Some brainstem tumours are diffuse midline gliomas, but others are different tumour types and are not classed as PDHGG.

References

References

Board, W.C. of T.E. (2022) Central Nervous System Tumours. Lyon: International Agency for Research on Cancer. ISBN: 9789283245087.

Capper, D. et al. (2018) ‘DNA methylation-based classification of central nervous system tumours’, Nature, 555(7697), pp. 469–474.

Clarke, M. et al. (2020) ‘Infant high-grade gliomas comprise multiple subgroups characterised by novel targetable gene fusions and favourable outcomes’, Cancer Discovery, 10(7), pp. 942–963.

Guerreiro Stucklin, A.S. et al. (2019) ‘Alterations in ALK/ROS1/NTRK/MET drive a group of infantile hemispheric gliomas’, Nature Communications, 10.

Korshunov, A. et al. (2017) ‘H3/IDH-wildtype paediatric glioblastoma is comprised of molecularly and prognostically distinct subtypes and associated oncogenic drivers’, Acta Neuropathologica, 134(3), pp. 507–516.

Louis, D.N. et al. (2007) ‘The WHO classification of tumours of the central nervous system’, Acta Neuropathologica, 114(2), pp. 97–109.

‘Paediatric high-grade gliomas: A comprehensive histopathological, immunohistochemical and molecular integrated approach in routine practice’ (2024) ScienceDirect.

‘European standard clinical practice recommendations for paediatric high-grade gliomas’ (2025) EJC Paediatric Oncology. Available at: View article.

This information is to provide general information and is NOT clinical information.