Introduction: When to Seek Diagnostic Testing

Neuroblastoma is most commonly diagnosed in very young children, with the majority of cases occurring before age 5. Parents or pediatricians often first notice something is wrong when a child develops unusual symptoms or when a mass is discovered during a routine examination. Because neuroblastoma can develop in different parts of the body and cause a wide variety of symptoms, knowing when to seek medical attention is important for early detection.^[1]

Children who should undergo diagnostic testing include those who have a noticeable lump in the abdomen, neck, or chest area. These lumps may be felt during a physical exam or noticed by parents during everyday activities like bathing or dressing their child. Other concerning signs that warrant medical evaluation include persistent bone pain, a swollen belly that makes breathing difficult, or unusual symptoms like bulging eyes or dark circles around the eyes that look like bruises.^[2]

Sometimes the symptoms are less specific but still troubling. A child might experience unexplained fevers, weight loss, or seem unusually tired for weeks. Some children develop weakness in their legs or have trouble walking, which can indicate that a tumor is pressing on the spinal cord. In babies, painless bluish lumps might appear under the skin. Because these symptoms can also occur with many other, less serious childhood illnesses, doctors need to perform specific tests to determine whether neuroblastoma is the cause.^[4]

In rare cases, children with a family history of neuroblastoma or certain genetic conditions may need regular screening even without symptoms. Families with known mutations in genes like ALK or PHOX2B (genes that control how cells grow and divide) should discuss monitoring plans with their healthcare team. Children with genetic syndromes such as Beckwith-Wiedemann syndrome, Li-Fraumeni syndrome, or neurofibromatosis type 1 are at increased risk and may benefit from periodic checks until age 10.^[11]

Classic Diagnostic Methods

Physical Examination

The diagnostic process typically begins with a thorough physical examination by a pediatrician or pediatric specialist. During this exam, the doctor will carefully feel different areas of the child’s body, looking for any unusual lumps or masses. The abdomen is examined closely because this is where neuroblastoma most often develops, particularly in the adrenal glands that sit on top of the kidneys. The doctor will also check the neck, chest, and areas along the spine for any abnormal growths.^[17]

The healthcare provider will ask detailed questions about when symptoms started, how they have changed over time, and whether there is any family history of cancer or genetic conditions. They will measure vital signs like blood pressure, which can sometimes be elevated if a neuroblastoma tumor is affecting the adrenal glands or kidneys. The doctor will also look for specific signs like bulging eyes, drooping eyelids, or unusual eye movements, which can occur when neuroblastoma spreads to certain areas.^[8]

Urine and Blood Tests

One of the most important early tests for neuroblastoma involves analyzing a child’s urine. Neuroblastoma cells often produce chemicals called catecholamines, which are hormone-like substances that the body breaks down and releases in urine. When these chemicals are measured in a urine sample, doctors look specifically for elevated levels of substances called vanillylmandelic acid (VMA) and homovanillic acid (HVA). Higher than normal amounts of these substances can indicate the presence of neuroblastoma.^[4]

Blood tests provide additional important information. Doctors may order a complete blood count to check for anemia, which means low red blood cells, or to see if the cancer has affected the bone marrow where blood cells are made. Other blood tests might measure substances like lactate dehydrogenase (LDH) and ferritin, which are proteins that can be elevated when neuroblastoma is present and can help doctors understand how aggressive the disease might be.^[7]

Imaging Studies

Imaging tests create detailed pictures of the inside of the body and are essential for finding tumors and seeing how large they are. An ultrasound is often the first imaging test performed, especially for babies and young children with abdominal symptoms. This test uses sound waves to create images and is completely painless. It works well for getting a first look at what might be causing a swelling or lump, though it cannot provide as much detail as other tests.^[17]

A CT scan (computed tomography scan) uses X-rays and computer technology to create detailed cross-sectional images of the body. This test can show the size and location of a tumor and whether it is affecting nearby organs or blood vessels. Children usually need to lie very still during the scan, and sometimes sedation is used for younger children who cannot remain motionless. A contrast dye may be given through an intravenous line to make the images clearer.^[17]

An MRI scan (magnetic resonance imaging) uses powerful magnets and radio waves instead of radiation to create detailed images. MRI is particularly useful for looking at tumors near the spinal cord or brain. Like CT scans, MRI requires the child to stay still, and the machine can be loud and enclosed, which some children find frightening. Sedation may be needed for young children, and child life specialists can help prepare children for what to expect.^[17]

For children where neuroblastoma is strongly suspected or confirmed, additional specialized scans may be performed. An MIBG scan (metaiodobenzylguanidine scan) is a nuclear medicine test that is very specific for neuroblastoma. A small amount of radioactive material is injected into the vein, and this substance is absorbed by neuroblastoma cells. A special camera then takes pictures over several days, showing exactly where neuroblastoma cells are located in the body, even in areas that other scans might miss.^[18]

A bone scan may be ordered to check whether neuroblastoma has spread to the bones, which unfortunately happens in many children by the time the cancer is diagnosed. Similarly, a PET scan (positron emission tomography) can show areas of increased cell activity throughout the body that might indicate cancer spread.^[7]

Biopsy

To confirm a neuroblastoma diagnosis with certainty, doctors need to examine actual tumor cells under a microscope. This requires obtaining a tissue sample through a procedure called a biopsy. During a biopsy, a surgeon removes a small piece of the tumor, or sometimes the entire tumor if it is small and easily accessible. This procedure is usually done under general anesthesia so the child does not feel any pain.^[4]

A pathologist, who is a doctor specially trained in examining tissues and cells, will study the biopsy sample under a microscope. They look at the size, shape, and arrangement of the cells to confirm whether they are neuroblastoma cells. The pathologist also examines how mature or immature the cells appear, because this affects how aggressive the cancer is likely to be and helps determine the best treatment approach.^[7]

Bone Marrow Examination

Because neuroblastoma commonly spreads to the bone marrow, which is the spongy tissue inside bones where blood cells are made, doctors need to check whether cancer cells are present there. This is done through a bone marrow aspiration and biopsy. A needle is inserted into the hip bone to withdraw a small amount of liquid marrow and a tiny piece of bone containing marrow. This is typically done under sedation or anesthesia to minimize discomfort. The marrow samples are then examined under a microscope to look for neuroblastoma cells.^[7]

Genetic and Molecular Testing

Once neuroblastoma is diagnosed, doctors perform specialized tests on the tumor cells to look for specific genetic changes. One of the most important tests checks for MYCN amplification, which means there are extra copies of the MYCN gene in the tumor cells. This finding is associated with more aggressive disease and affects treatment decisions. About 25 percent of neuroblastoma patients have MYCN amplification.^[3]

Other genetic tests look for chromosome abnormalities, such as loss of parts of chromosome 1p or 11q, or gain of chromosome 17q. These findings help doctors classify the neuroblastoma into risk groups and predict how the tumor is likely to behave. Testing may also look for mutations in the ALK gene, which occurs in some neuroblastomas and might influence treatment choices.^[7]

Diagnostics for Clinical Trial Qualification

When families consider enrolling their child in a clinical trial to access new or experimental treatments, additional specific tests may be required. Clinical trials have strict eligibility criteria to ensure that the study results are reliable and that participants are appropriate candidates for the experimental treatment being tested. Understanding these requirements helps families prepare for the enrollment process.

Most clinical trials require complete baseline documentation of the extent of disease before treatment begins. This typically includes all the standard diagnostic tests described above: imaging studies like CT scans, MRI, and MIBG scans to map exactly where the neuroblastoma is located and how large the tumors are. These baseline scans serve as a reference point for measuring whether the treatment is working later on.^[7]

Bone marrow examinations are usually mandatory for clinical trial enrollment, even if previous tests suggested the marrow is clear. Trials need precise documentation about whether cancer cells are present in the bone marrow at the start of treatment. This information is critical for determining the child’s risk category and for accurately measuring treatment response.

Blood and urine tests measuring catecholamine breakdown products (VMA and HVA) are standard requirements. Trials often specify exactly how these samples should be collected and processed. Some trials require 24-hour urine collections, where all urine produced over a full day is gathered and tested, to get the most accurate measurements.

Genetic and molecular testing of the tumor is essential for many clinical trials, particularly those testing treatments targeted at specific genetic abnormalities. Trials may require fresh tumor tissue for molecular analysis, which might necessitate a new biopsy even if one was done previously. Testing for MYCN status, chromosome abnormalities, and specific gene mutations must usually be performed at certified laboratories using standardized methods to ensure accuracy.^[7]

Organ function tests are required to verify that a child’s major organs can tolerate the trial treatment. These include kidney function tests (measuring creatinine and glomerular filtration rate), liver function tests (checking enzymes and bilirubin levels), heart function tests (usually an echocardiogram or cardiac ultrasound to measure how well the heart pumps), and sometimes hearing tests. These baseline measurements protect children from receiving treatments that their bodies cannot safely process.^[15]

For some trials, particularly those involving immunotherapy, additional specialized blood tests may be needed to assess the child’s immune system function. These might include measuring specific immune cell populations or checking for antibodies that could interfere with treatment.

Documentation of previous treatments is thoroughly reviewed for clinical trials. If a child has already received any chemotherapy, surgery, or other cancer treatment, detailed records must be provided. Some trials are only open to newly diagnosed patients who have not yet received treatment, while others specifically enroll children whose cancer has returned or did not respond to initial therapy.

Performance status assessment, which evaluates how well a child can perform daily activities, is a standard requirement. For very young children who cannot report symptoms themselves, parents and doctors assess factors like feeding ability, alertness, and overall activity level. Older children might be asked questions about whether they can play, attend school, or perform self-care activities.

Age and weight requirements vary by trial. Some experimental treatments are only tested in specific age ranges, and dosing calculations often depend on accurate measurements of the child’s body surface area, which is calculated from height and weight. Precise measurements must be documented at enrollment.

Trials testing new diagnostic methods or imaging techniques may require children to undergo experimental scans or tests in addition to standard diagnostics. These investigational procedures must be clearly explained to families as part of the informed consent process, and families have the right to decline participation if they have concerns.