Pediatric CNS Tumor Types Explained

"Brain tumor" is not one diagnosis. In children it covers many separate diseases. They start in different cells, sit in different places, are treated differently, and have very different outlooks.

Getting the exact name matters more than almost anything else in the first week.

Many childhood central nervous system (CNS) tumors block the flow of cerebrospinal fluid. Pressure builds inside the skull. The National Cancer Institute lists these signs for childhood glioma:

• Morning headache, or a headache that goes away after vomiting.
• Nausea and vomiting.
• Problems with vision, hearing, or speech.
• Loss of balance and trouble walking.
• Weakness, or a change in feeling on one side of the body.
• Unusual sleepiness.
• More or less energy than usual.
• Change in personality or behavior.
• Seizures.
• Weight loss or weight gain for no known reason.
• An increase in the size of the head, in infants.

Call 911 for a first seizure, a child who is hard to wake or cannot be roused, or sudden weakness on one side. Rising pressure inside the skull is an emergency, and it can worsen within hours, so call for an ambulance rather than driving. Get emergency care the same way for repeated vomiting with headache, new double vision, or a bulging soft spot in a baby.

In 2024, an estimated 14,910 children and adolescents aged 0 to 19 were expected to be diagnosed with cancer in the United States, and 1,590 to die of it. Malignant brain and other CNS tumors are among the most common types diagnosed in children, second only to leukemias.

More than 90% of children and adolescents diagnosed with cancer in the United States are cared for at a center affiliated with the NCI-supported Children's Oncology Group. If your child is not at one, ask why.

The National Cancer Institute organizes childhood CNS tumors into these groups:

• Childhood glioma, including astrocytoma.
• Childhood ependymoma.
• Childhood diffuse intrinsic pontine glioma (DIPG).
• Childhood atypical teratoid/rhabdoid tumor.
• Childhood medulloblastoma and other CNS embryonal tumors.
• Childhood CNS germ cell tumors.
• Childhood craniopharyngioma.

Gliomas start in glial cells, the supporting cells of the brain. They are the largest group.

Gliomas have four grades. They are most often grouped into low grade (I or II) or high grade (III or IV).

Low-grade gliomas grow slowly and do not spread within the brain and spinal cord. Pilocytic astrocytoma is the best-known type. Children with a low-grade glioma, astrocytoma, neuronal tumor, or glioneuronal tumor have a relatively favorable prognosis if the tumor can be removed by surgery.

High-grade gliomas are fast growing and often spread within the brain and spinal cord, which makes them harder to treat. Children with a high-grade glioma have a poor prognosis.

Other named types include diffuse astrocytoma, diffuse pediatric-type high-grade glioma, high-grade astrocytoma with piloid features, and pleomorphic xanthoastrocytoma.

Two genetic conditions raise glioma risk in children: neurofibromatosis type 1 (NF1) and tuberous sclerosis. If either runs in your family, say so.

Diffuse intrinsic pontine glioma is a fast-growing tumor that starts in the part of the brain stem called the pons. It mainly affects children between ages 5 and 10, but it can occur in younger children and teens.

Its signs come from the cranial nerves that run through the pons:

• Trouble with eye movement.
• Vision problems.
• Problems with talking, chewing, and swallowing.
• Drooping on one side of the face.
• Morning headache, or headache that goes away after vomiting.
• Nausea and vomiting.
• Weakness in the arms or legs.
• Loss of balance and trouble walking.
• Changes in behavior.
• Trouble learning in school.

DIPG is diagnosed with MRI, with or without gadolinium contrast. A biopsy, in which a surgeon takes a sample of tumor tissue from the pons, may be done.

Surgery to remove it is not an option. The pons controls breathing, heart rate, and blood pressure, and carries the nerves used in seeing, hearing, walking, talking, and eating.

DIPG is treated with external-beam radiation therapy. Radiation often improves symptoms for a period of time.

The outlook is poor, and you deserve to hear it plainly. Most children with DIPG do not live longer than 2 years after diagnosis. Ask about clinical trials early, and ask about palliative care from the beginning rather than at the end.

Ependymoma is a rare tumor that starts in the brain or spinal cord. It begins in ependymal cells, which line the ventricles and passageways of the brain and spinal cord and make cerebrospinal fluid.

Because these tumors sit in the fluid pathways, cells can be carried to other parts of the brain and spinal cord. They rarely spread outside the CNS.

Ependymomas are grouped by grade and by location: posterior fossa, supratentorial, and spinal cord.

Surgery to remove the tumor, and some healthy tissue around it, is usually the first treatment. Complete removal matters: the prognosis is better if the cancer can be completely removed. Radiation therapy is commonly given after surgery.

If the first operation did not remove everything, ask whether a second-look operation is possible, and whether a higher-volume surgical center should review the scans.

CNS embryonal tumors form in cells left over from fetal development, called embryonal cells.

Medulloblastoma is a fast-growing tumor that forms in the cerebellum, the lower, back part of the brain. It is the most common tumor in this group.

Pineoblastoma is a fast-growing tumor that forms in or around the pineal gland, a tiny organ near the center of the brain.

Other types include embryonal tumors with multilayered rosettes (ETMR), cribriform neuroepithelial tumors, CNS neuroblastomas, and medulloepitheliomas.

Atypical teratoid/rhabdoid tumor (AT/RT) is also an embryonal tumor, but it is treated differently.

These tumors tend to spread through the cerebrospinal fluid to other parts of the brain and spinal cord. That is why staging includes an MRI of the whole spine and a spinal fluid sample.

Symptoms include loss of balance, trouble walking, lack of coordination, slow speech, headache, general weakness, weakness on one side of the face, unusual sleepiness, seizures, double vision or other eye problems, and nausea and vomiting.

For medulloblastoma, treatment depends on whether the tumor is average risk or high risk. That turns on how much was removed by surgery and whether it has spread.

Treatment may involve surgery, radiation therapy, chemotherapy, high-dose chemotherapy with stem cell rescue, and targeted therapy such as vismodegib.

• What is the exact tumor name, grade, and molecular result on the pathology report?
• Has the case been reviewed by a pediatric neuropathologist?
• Did the MRI include the whole spine, and was spinal fluid sampled?
• How much of the tumor was removed, and is more surgery possible?
• Is my child eligible for a Children's Oncology Group trial?
• What late effects should we expect from this specific treatment plan?

Molecular testing has changed how these tumors are classified. Two that look identical under a microscope can behave very differently. Ask whether it is being done, and ask to see the result in writing.

• Childhood Brain and Spinal Cord Tumors — NCI
• Childhood Glioma and Astrocytoma — NCI
• Childhood Diffuse Intrinsic Pontine Glioma (DIPG) — NCI
• Childhood Ependymoma — NCI
• Childhood Medulloblastoma and Other CNS Embryonal Tumors — NCI
• Cancer in Children and Adolescents — NCI