Diagnosing atypical teratoid/rhabdoid tumour (ATRT) requires a combination of imaging studies and tissue analysis to confirm the presence of this rare and aggressive brain tumor. Because symptoms can develop rapidly and mimic other common childhood illnesses, prompt and accurate testing is essential for starting appropriate care.

Who Should Undergo Diagnostics and When to Seek Testing

Parents and caregivers should consider seeking medical evaluation when a child displays certain warning signs, especially if these symptoms appear suddenly and worsen quickly over days or weeks. This rapid progression is characteristic of ATRT due to its fast-growing nature. Children younger than three years old are at highest risk, though the tumor can occur in older children and adults as well.

It is advisable to consult a doctor if your child experiences morning headaches that are particularly severe upon waking. These headaches may be accompanied by nausea and vomiting, which often improve as the day progresses. This pattern occurs because fluid can build up in the brain while lying down during sleep, increasing pressure inside the skull.^[1]

Parents should also watch for changes in their child’s activity level or unusual sleepiness and lethargy. Difficulty with balance, coordination, or walking can signal that a tumor is affecting parts of the brain responsible for movement. In infants, a noticeable increase in head size or a bulging soft spot on the skull may indicate fluid buildup in the brain, a condition called hydrocephalus—where cerebrospinal fluid accumulates and cannot drain properly.^[1][6]

Because ATRT symptoms can resemble those of more common childhood illnesses, it’s important not to dismiss persistent or worsening signs. If traditional treatments don’t improve your child’s condition, further investigation through diagnostic testing becomes necessary. Early detection can make a significant difference in treatment planning and outcomes.^[6]

Diagnostic Methods for Identifying ATRT

The diagnostic process for ATRT begins with comprehensive physical and neurological examinations. During these initial assessments, your child’s doctor will gather information about symptoms, medical history, and family health background. The neurological exam evaluates functions such as coordination, reflexes, vision, hearing, and muscle strength to identify areas potentially affected by a tumor.^[6][10]

Magnetic Resonance Imaging (MRI)

An MRI scan is the primary imaging tool used to detect ATRT. This test uses powerful magnets, radio waves, and a computer to create detailed pictures of the brain and spinal cord without using radiation. Unlike X-rays or CT scans, MRI provides exceptional clarity of soft tissues, making it ideal for examining brain structures.^[6]

On an MRI, ATRT typically appears as a very large mass with fluid-filled areas. When a contrast dye is injected into a vein before the scan, the tumor often brightens, helping doctors see its boundaries more clearly. The images may also reveal areas of bleeding or dead tissue within the tumor. Because ATRT can spread through the cerebrospinal fluid—the clear liquid that surrounds the brain and spinal cord—doctors will order MRI scans of both the brain and the entire spine to check for tumor spread.^[2][18]

Lumbar Puncture (Spinal Tap)

A lumbar puncture is performed to examine cerebrospinal fluid for the presence of tumor cells. During this procedure, a thin needle is inserted between the bones of the lower spine to collect a small sample of fluid. The sample is then analyzed under a microscope to determine if cancer cells have spread beyond the original tumor location. This test is crucial for staging the disease and understanding how extensively the tumor has spread through the central nervous system.^[6][18]

Biopsy and Tumor Tissue Analysis

The definitive diagnosis of ATRT requires removing a piece of tumor tissue for detailed examination under a microscope. In many cases, this biopsy is performed during surgery to remove as much of the tumor as possible. A specialized doctor called a neuropathologist—an expert in examining brain and nervous system tissues—reviews the sample to confirm the diagnosis.^[2][10]

What makes ATRT distinctive is the loss of specific proteins in the tumor cells. The diagnosis is confirmed through immunohistochemical staining, a laboratory technique that identifies whether certain proteins are present or absent. In ATRT, tumor cells lack either the INI1 protein (from the SMARCB1 gene) or the BRG1 protein (from the SMARCA4 gene). This absence of protein is the hallmark finding that confirms the tumor is an ATRT rather than another type of brain tumor.^[2][12]

Genetic Testing

Genetic testing is recommended for children diagnosed with ATRT to determine whether the gene mutation that caused the tumor was inherited from parents or occurred spontaneously. This testing looks for changes in the SMARCB1 or SMARCA4 genes in the child’s regular body cells, not just in the tumor. These genes are tumor suppressor genes, which normally make proteins that help control cell growth and prevent tumors from forming.^[6][10]

If the genetic change is found in the child’s normal cells, it means the mutation was inherited and the child has a condition called rhabdoid tumor predisposition syndrome. Children with this inherited condition have a higher risk of developing additional tumors, both in the brain and in other parts of the body such as the kidneys. When an inherited mutation is identified, genetic counseling is recommended for the family. This involves meeting with a trained professional who can explain the condition, discuss the risk to other family members, and provide guidance about monitoring and testing.^[10][12]

Interestingly, researchers have identified three distinct groups of ATRT based on their genetic and molecular characteristics: AT/RT-TYR, AT/RT-SHH, and AT/RT-MYC. Each group tends to occur in different locations within the central nervous system and is more common in different age groups. The AT/RT-MYC subtype is the most frequently seen in adults, though adult cases remain extremely rare overall.^[2][18]

Additional Imaging Studies

Depending on the initial findings, doctors may order additional imaging tests to get a complete picture of the tumor’s extent. While MRI remains the gold standard, a CT scan (computed tomography) may be used in emergency situations or when MRI is not immediately available. CT scans use X-rays and computer processing to create cross-sectional images of the body, though they provide less detail of soft tissues compared to MRI.^[1]

Diagnostics for Clinical Trial Qualification

When patients are being considered for enrollment in clinical trials testing new treatments for ATRT, specific diagnostic criteria must be met. These standardized requirements ensure that researchers are studying treatments in patients with confirmed ATRT and that results can be accurately compared across different studies and treatment centers.

Clinical trials typically require confirmation of the diagnosis through both imaging and tissue analysis. This means patients must have had a biopsy or surgical removal of the tumor, with laboratory confirmation showing the loss of INI1 or BRG1 protein. The tissue sample is often reviewed by multiple pathologists to ensure diagnostic accuracy, particularly for such a rare tumor type.^[2]

Staging tests are essential for clinical trial enrollment. These tests determine whether the tumor is localized (confined to one area) or disseminated (spread to multiple locations in the brain, spinal cord, or body). Complete staging requires MRI scans of both the brain and the entire spine, as well as examination of cerebrospinal fluid through lumbar puncture. These tests must show whether tumor cells have spread through the fluid pathways of the central nervous system.^[2][18]

Genetic testing results indicating whether the child has inherited or spontaneous SMARCB1 or SMARCA4 mutations may also influence trial eligibility. Some clinical trials are specifically designed for patients with particular genetic subtypes of ATRT, while others may have criteria related to whether the tumor is a first occurrence or a recurrence.^[10]

Baseline health assessments are another requirement for clinical trial participation. These typically include blood tests to check organ function, particularly of the kidneys, liver, and bone marrow. Because treatments for ATRT can be intensive, patients must have adequate organ function to safely undergo the therapies being studied. Tests may include complete blood counts, liver function tests, kidney function tests, and assessments of heart function through electrocardiogram or echocardiogram.^[10]

Age is often a critical factor in clinical trial eligibility for ATRT. Since this tumor predominantly affects very young children—most commonly those under three years old—many trials are specifically designed for pediatric patients. However, the rapid growth in understanding ATRT’s molecular characteristics has led to trials examining whether treatments can be tailored to specific genetic subtypes regardless of age.^[2][12]

Documentation of any previous treatments is also necessary for clinical trial enrollment. This includes details about prior surgeries, chemotherapy regimens, radiation therapy, and the patient’s response to those treatments. For trials studying recurrent ATRT, specific criteria about the timing and nature of the recurrence must be met, often requiring new imaging and sometimes repeat biopsies to confirm active tumor growth.^[10]

Performance status assessments evaluate how well patients can carry out daily activities. For very young children, this includes developmental milestones and overall functional capacity. Clinical trials need to enroll patients who are well enough to tolerate the experimental treatments while still having active disease that requires therapy. These assessments help ensure patient safety while allowing researchers to evaluate treatment effectiveness.^[10]

Finally, informed consent is a crucial part of the clinical trial enrollment process. For pediatric patients, parents or legal guardians must understand the nature of the study, potential benefits and risks, alternative treatment options, and their right to withdraw at any time. This process ensures families can make informed decisions about participating in research while their child receives care for ATRT.