ATRTs are classified as embryonal tumours, meaning that they develop from stem cells that helped the embryo to form in the womb, but have unfortunately remained active in the brain after birth. When these stem cells fail to stop dividing and developing after the child is born, they can form a cancerous tumour.

Where do atypical teratoid rhabdoid tumours (ATRTs) occur?

Atypical teratoid rhabdoid tumours (ATRTs) can be found anywhere in the brain or spinal cord, which together make up the central nervous system (CNS). They tend to begin in the brain and spread to the spinal cord rather than beginning in the spinal cord, although this has been reported in some cases. 

For some patients, other forms of rhabdoid tumours may also be discovered in the kidney and other soft tissues, so a full body MRI scan is likely to be offered in order to clarify the full diagnosis. 

Atypical teratoid rhabdoid tumour (ATRT) classification

Atypical teratoid rhabdoid tumour (ATRT) is usually classified as a World Health Organisation (WHO) Grade 4 tumour, which means that it is a fast-growing form of brain cancer. Due to the rarity of this tumour, there is no standard staging system, so tumours are simply described as either newly diagnosed or recurrent.

Due to their similar appearance under a microscope, atypical teratoid rhabdoid tumours (ATRTs) often used to be diagnosed as Primitive Neuroectodermal tumours (PNETs) or as Medulloblastomas before the introduction of SMARCB1 and SMARCA4 as molecular markers, which sets them apart from these closely related paediatric brain tumours.  SMARCB1 and SMARCA4 are both tumour suppressor genes. Changes in the DNA of these genes means that they then fail to give the signal for a protein to be produced that controls cell growth, and so the body is unable to stop or “suppress” tumours from forming.

Recent research has highlighted three subgroups of atypical teratoid rhabdoid tumours, each with distinct clinical and molecular characteristics: meaning the symptoms that they present within the child, and how they can be categorised using the type of genetic profiling mentioned above. Each subgroup of ATRT tumours offers different options for personalised treatment, and researchers are working to establish the best treatment combination for each tumour, so discussing clinical trial options with the patient’s medical team is a route that is often taken by parents of children with this tumour type.

The development of an atypical teratoid rhabdoid tumour (ATRT) is generally agreed by scientists to be caused by mutations in the DNA of two genes that help to control cell growth. Known as “tumour suppressor genes”, they have been given the names SMARCB1 and SMARCA4 and are explained in more detail above.

Such genetic changes may be spontaneous (appearing for the first time in a family) or inherited. For example, the inherited genetic condition schwannomatosis may predispose someone to develop an ATRT tumour.

If the genetic mutation is inherited, the risk of rhabdoid tumours forming in different parts of the body (for example the kidneys) as well as in the brain is increased.  However, reports to date of the tumour being diagnosed in more than one family member are extremely rare.

What are the symptoms of an atypical teratoid rhabdoid tumour (ATRT)?

The symptoms vary according to the tumour location and the age of the patient, which sometimes makes this tumour difficult to diagnose. However because these are fast-growing tumours, the symptoms can both appear and progress quickly. In infants you may see an increase in the size of the head, and for patients of all ages the most common symptoms are:

•Headaches, particularly after having laid down and slept all night
•Vomiting
•Changes in activity levels
•Loss of balance

You can read more about brain tumour symptoms here.

Discover more about how a brain tumour is diagnosed.

The first line of treatment would usually be surgery, in order to remove as much of the tumour as possible and to obtain a biopsy (a sample of the tumour tissue that can then be analysed in a laboratory).

Guided by the age of the patient, the position of the tumour, how much tumour remains and the results of the biopsy, surgery is usually followed by chemotherapy and radiotherapy, sometimes with the addition of specialised drugs designed to target the particular molecular markers of the patient’s tumour type.