Atypical teratoid/rhabdoid tumor (AT/RT)

AT/RT is a very rare, fast-growing cancer that begins in the brain or spinal cord (the central nervous system, or CNS). Doctors call it an embryonal tumor, a type thought to start in very immature cells. It is a high-grade (grade 4) tumor, which means it grows fast. It usually affects children aged 3 and younger, but it can also occur in older children and adults.

St. Jude Children’s Research Hospital says AT/RT is the most common cancerous brain or spinal cord tumor in babies under 1 year old. About half of these tumors form in the cerebellum or brain stem, at the back and base of the brain. The cerebellum controls movement and balance. The brain stem controls breathing, heart rate and the nerves used for seeing, hearing, walking, talking and eating. AT/RT can also start in other parts of the brain and spinal cord.

AT/RT belongs to a larger family called rhabdoid tumors. Rhabdoid tumors can also form outside the brain, for example in the kidney. AT/RT was first described as its own disease in 1987. Before then it was usually labeled as another brain tumor, such as medulloblastoma.

AT/RT is linked to changes in a gene called SMARCB1 (also called INI1). Less often, the change is in a gene called SMARCA4. Both are tumor suppressor genes. Normally they make proteins that help control how and when cells grow. When a gene like this stops working, cells can grow out of control. Doctors now define AT/RT by a change in one of these two genes.

In most children, the gene change is found only in the tumor. But up to about 1 in 3 children with AT/RT (up to 35% in U.S. National Cancer Institute figures) are born with the change in every cell of the body. This is called rhabdoid tumor predisposition syndrome (RTPS). Children with RTPS are usually diagnosed younger, and they can have more than one tumor at the same time, such as in the brain and the kidney.

MedlinePlus Genetics says that when RTPS is caused by a SMARCB1 change, it usually appears for the first time in the child, with no family history. When the change is in SMARCA4, it is most often passed down from a parent who carries it but never had a tumor. The U.S. National Cancer Institute adds that a parent can also carry a SMARCB1 change without having a tumor. In a few families, more than one child has had AT/RT even though tests found the change in neither parent. For these reasons, care teams usually offer genetic counseling and testing to the child and family.

Because AT/RT grows quickly, symptoms often appear and get worse over days or weeks. Many symptoms come from pressure inside the head, often because the tumor blocks the flow of the fluid around the brain (hydrocephalus). Common signs include morning headaches or headaches that ease after vomiting, nausea and vomiting, unusual sleepiness, and loss of balance or trouble walking. In babies, the head may grow bigger and the soft spot on top of the head may bulge.

Some children lose movement skills they had already learned. Others have pain, tingling, numbness or loss of movement (paralysis) in the face, or unusual eye or face movements, because the tumor affects the nerves there. Changes in personality or behavior and irritability can also occur.

AT/RT can spread through the fluid around the brain and spinal cord (cerebrospinal fluid) to other parts of the brain and spine. Registry data suggest that 25% to 30% of children already have spread when they are diagnosed.

Treatment is intense. A pediatric oncologist leads a team that often includes a neurosurgeon, radiation oncologist, neurologist, nurse specialists, rehabilitation therapists, a psychologist, a social worker and a genetic counselor. The U.S. National Cancer Institute also lists a fertility specialist. The high doses of chemotherapy can cause bleeding and raise the risk of infection.

The side effects can be serious. In the ACNS0333 trial, 4 of 65 patients (6%) died from treatment complications: severe infection, breathing failure or brain tissue damage. Some children also need steroid or seizure medicines, and medicine for nausea.

Children who finish treatment have regular checkups and imaging scans. St. Jude lists problems with learning, thinking and memory, hormone (endocrine) problems and second cancers among the possible late effects. Children with rhabdoid tumor predisposition syndrome also need regular kidney ultrasounds to watch for new tumors.

St. Jude says it is important to balance quality of life with cancer treatment. Palliative care and quality-of-life teams can help families manage symptoms and side effects, have difficult conversations and make decisions that match their wishes.

No donor is involved in treating AT/RT. When high-dose chemotherapy with stem cell rescue is part of the plan, it uses the child’s own stem cells. They are collected and frozen before the high-dose treatment and returned afterward. No registry donor and no donor search is needed.

The rescue is there to rebuild the blood and immune system after chemotherapy strong enough to wipe out the bone marrow. The U.S. National Cancer Institute says stem cell transplants do not usually work against cancer directly. It explains that fighting cancer directly with donor immune cells, called the graft-versus-tumor effect, comes from donor transplants, mainly in leukemia. European transplant experts (EBMT, 2025) say donor transplants for children’s brain tumors are generally not recommended.

For families facing AT/RT, joining a stem cell donor registry is not a need of their own. It is a way to help other patients, such as children with leukemia, who do need a donor.