Atypical teratoid/rhabdoid tumour (ATRT) — understanding your child's diagnosis

ATRT stands for Atypical Teratoid/Rhabdoid Tumour — a rare, fast-growing malignant brain (or spinal cord) tumour that occurs almost exclusively in young children, with most cases diagnosed before the age of three. What sets ATRT apart from other childhood brain tumours is its molecular fingerprint: the vast majority of ATRTs are caused by a change (inactivation) in a gene called SMARCB1 (also known as INI1) or, less commonly, SMARCA4 (BRG1). This genetic change can be identified in the tumour tissue after a biopsy and is now considered essential for a definitive diagnosis. Without this molecular testing, ATRT can look similar to other embryonal tumours under the microscope, which is why expert pathology review at a specialist centre is critical. CION’s paediatric oncology team ensures every diagnosis is verified by experienced pathologists before any treatment discussions begin.

Because ATRT most commonly affects very young children — often infants under 18 months — the symptoms can differ from those seen in older children with brain tumours. In infants, parents and caregivers often notice: a rapid or unusual increase in head size (head circumference), a tense or bulging soft spot (fontanelle), persistent and unexplained irritability, difficulty feeding, and vomiting that does not settle. In toddlers and older young children, symptoms may include new or worsening morning headaches, repeated vomiting (especially in the morning, without obvious cause), balance and walking problems, double vision or an eye that has started to turn, or loss of a developmental skill the child had already mastered. These symptoms are also seen in many non-serious childhood illnesses, but if they are persistent, worsening, or appearing together, a prompt medical review is the right step. None of these symptoms should be waited out at home for more than a few days before speaking to a doctor.

Diagnosis of ATRT in children involves several steps. First, a brain MRI with contrast is usually obtained — ATRT tumours can appear in any part of the brain or spinal cord, and the MRI helps define the tumour’s location, size, and relationship to surrounding structures. Because ATRT can spread through the cerebrospinal fluid (CSF), imaging of the entire spine is also typically done. A sample of CSF may be taken (lumbar puncture) to check for tumour cells. The definitive diagnosis requires surgical removal of a sample of the tumour (biopsy or, where possible, surgical resection) followed by detailed pathological analysis — both conventional examination under the microscope and molecular testing for the loss of INI1 or BRG1 protein expression. Because a small percentage of patients have ATRT as part of a hereditary syndrome (Rhabdoid Tumour Predisposition Syndrome), genetic counselling for the family may also be recommended after diagnosis. At CION, every paediatric brain tumour case is reviewed at a multidisciplinary tumour board before any treatment is planned.

ATRT is a medically complex tumour, and treatment is highly individualised based on the child’s age, the tumour’s location, whether it has spread through the CSF, and the extent of surgical removal. Treatment typically involves a combination of surgery, chemotherapy, and, in appropriate cases, radiation therapy. Surgery aims to remove as much of the tumour as is safely possible. Chemotherapy plays a central role — specific chemotherapy regimens designed for ATRT have been developed through international collaborative studies and differ from those used in other childhood brain tumours. Radiation therapy is effective against ATRT but its use in very young children requires careful consideration because of the potential impact on the developing brain. This is why treatment decisions for infants are often different from those for older children. The CION paediatric oncology team discusses every case at a dedicated tumour board — bringing together paediatric oncologists, neurosurgeons, radiation oncologists, and neuroradiologists — to ensure each child receives a coordinated, evidence-based plan tailored to their specific situation.

In most children diagnosed with ATRT, the genetic change in SMARCB1 or SMARCA4 occurs only in the tumour cells and is not inherited. However, in a minority of cases — particularly in very young infants, or when a family member has had a rhabdoid tumour — the change can be present in all cells of the body as a germline (inherited) mutation. This condition is called Rhabdoid Tumour Predisposition Syndrome (RTPS) and carries a risk of rhabdoid tumours at multiple sites. For this reason, genetic counselling is recommended for families of children diagnosed with ATRT, especially when the child is very young or there is a family history. Genetic testing can determine whether the mutation is germline (inherited, present in all cells) or somatic (confined to the tumour). If a germline mutation is found, other family members may be offered testing. The CION team will guide your family through this process with sensitivity and clarity.

An ATRT diagnosis is one of the most challenging experiences a family can face. At CION, we walk this journey with you — not just the medical aspects, but the emotional, practical, and developmental dimensions as well. Our allied care team includes a dedicated psycho-oncologist for children and parents, a paediatric nutritionist to support your child’s wellbeing during treatment, physiotherapy and occupational therapy support for motor skills and development, and guidance on school-reintegration for children who are well enough to return. We provide transparent, plain-language explanations at every step — before any treatment begins, before any procedure, and at every review. Our 45-minute consultations are designed so you have enough time to ask every question. You will never feel rushed, and every decision will be explained to you clearly before any action is taken. We also connect families with peer support networks and social work resources, because no parent should feel alone in this.