Types of Brain and Spinal Cord Tumors in Children

Many different types of tumors can occur in the brain and spinal cord. Several factors are important when doctors are trying to figure out how best to treat a tumor and what the prognosis (outlook) is likely to be. 

The type of tumor (based on the type of cell it starts from): Tumors can form in almost any type of tissue or cell in the brain or spinal cord. Some tumors have a mix of cell types. Different types of tumors tend to start in certain parts of the brain or spinal cord, and tend to grow in certain ways. (The most common types of brain and spinal cord tumors in children are described below.)

The grade of the tumor: Some types of brain and spinal cord tumors are more likely to grow into nearby tissues (and to grow quickly) than are others. Brain and spinal cord tumors are typically divided into 4 grades (using Roman numerals I to IV), based largely on how the tumor cells look under a microscope. The higher the grade, the more quickly the tumor is likely to grow: 

• Lower grade (grade I or II) tumors tend to grow more slowly and are less likely to grow into (invade or infiltrate) nearby tissues.
• Higher grade (grade III or IV) tumors tend to grow quickly and are more likely to grow into nearby tissues. These tumors often require more intensive treatment.

Gene changes in the tumor cells: Even for a specific type of tumor, the changes in the genes of the tumor cells can be different. For example, many types of tumors are now divided based on whether the cells have mutations in one of the IDH genes. For a specific type of tumor, those with IDH mutations tend to have a better outlook than those without a mutation. Other gene mutations can also be important for certain types of tumors.

The location of the tumor: Where the tumor is in the brain and spinal cord can affect what symptoms it causes, as well as which treatments might be best. Brain tumors in children are more likely to start in the lower parts of the brain, such as the cerebellum and brain stem, than they are in adults. But they can start in the upper parts of the brain as well.

Gliomas

Gliomas are not a specific type of tumor. Glioma is a general term for a group of tumors that start in glial cells (the supporting cells of the brain). A number of tumors can be considered gliomas, including:

• Astrocytomas (which include glioblastomas)
• Oligodendrogliomas
• Ependymomas
• Brain stem gliomas
• Optic gliomas

About half of all brain and spinal cord tumors in children are gliomas.

Astrocytomas

Astrocytomas are tumors that start in cells called astrocytes, a kind of glial cell that helps support and nourish nerve cells.

Some astrocytomas can spread widely throughout the brain and blend with the normal brain tissue, which can make them hard to remove by surgery. Sometimes they spread along the cerebrospinal fluid (CSF) pathways. It is very rare for them to spread outside of the brain or spinal cord.

As with other brain tumors, astrocytomas are often grouped by grade.

Low-grade (grade I or II) astrocytomas tend to grow slowly and are the most common type in children. Some types, known as non-infiltrating astrocytomas, are grade I tumors that tend to grow very slowly and do not grow into (infiltrate) nearby tissues, so they often have a good prognosis.

• Pilocytic astrocytomas are grade I tumors that tend to grow slowly and rarely grow into nearby tissues. They most commonly occur in the cerebellum but can also begin in the optic nerve, hypothalamus, brain stem, or other areas. They account for nearly 1 out of 5 brain tumors in children.
• Subependymal giant cell astrocytomas (SEGAs) occur in the ventricles (spaces in the brain). They are grade I tumors that tend to grow slowly and rarely grow into nearby tissues. These tumors are almost always linked with an inherited condition called tuberous sclerosis.
• Diffuse astrocytomas are also slow-growing tumors, but they are grade II tumors that can grow into nearby tissues, which makes them hard to remove with surgery. Though these tumors are thought of as low grade, they tend to become more aggressive and fast growing over time.
• Pleomorphic xanthoastrocytomas (PXAs) are grade II tumors that tend to grow slowly, and most can be cured by surgery alone.
• Optic gliomas are astrocytomas that start in the optic nerves (the nerves leading from the eyes to the brain). They usually grow slowly, and are often linked with an inherited condition called neurofibromatosis type 1. These tumors are rarely fatal, but they may cause vision loss and injury to nearby brain tissue.

High-grade (grade III or IV) astrocytomas tend to grow quickly and spread into the surrounding normal brain tissue. These include:

• Glioblastomas, which are the fastest growing type of astrocytoma (grade IV). 
• Anaplastic astrocytomas, which are grade III.

Oligodendrogliomas

These tumors start in brain cells called oligodendrocytes (a type of glial cell that makes a fatty substance that helps nerve cells send electric signals). These are grade II tumors that tend to grow slowly, but most of them can grow into nearby brain tissue and can’t be removed completely by surgery. Oligodendrogliomas rarely spread along the CSF pathways and even less frequently spread outside the brain or spinal cord. As with astrocytomas, they can become more aggressive over time.

Only about 1% of brain tumors in children are oligodendrogliomas.

Ependymomas

About 5% of brain tumors in children are ependymomas. These tumors start in the ependymal cells that line the ventricles or central canal of the spinal cord. They can range from fairly low-grade (slow growing) tumors to grade III (fast growing) tumors, which are called anaplastic ependymomas.

Ependymomas may spread along the CSF pathways but do not spread outside the brain or spinal cord. These tumors can block the flow of CSF out of the ventricles, causing the ventricles to become very large – a condition called hydrocephalus.

Unlike astrocytomas and oligodendrogliomas, ependymomas usually do not grow into normal brain tissue. As a result, some (but not all) ependymomas can be removed and cured by surgery. But because they can spread along ependymal surfaces and CSF pathways, treating them can sometimes be difficult.

Brain stem gliomas

A brain stem glioma is any type of glioma that starts in the brain stem. This term refers to the location of the tumor, rather than the type of cell it starts in.

• A small number of brain stem gliomas occur as tumors with very distinct edges (called focal brain stem gliomas).
• More often, brain stem gliomas grow diffusely throughout the brain stem (where the tumor cells are spread throughout normal tissue), rather than growing as a focal tumor (where the tumor cells are clustered together). These are referred to as diffuse midline gliomas. These tumors most often start in the pons, where they are called diffuse intrinsic pontine gliomas (DIPGs). These tumors can be hard to treat.

About 10% to 20% of brain tumors in children are brain stem gliomas. Nearly all of these tumors are some type of astrocytoma.

Embryonal tumors

These tumors start in early forms of nerve cells in the central nervous system. About 10% to 20% of brain tumors in children are embryonal tumors. They are more common in younger children than older ones, and are rare in adults. Embryonal tumors tend to grow quickly and often spread throughout the CSF pathways. 

Medulloblastomas are the most common type of embryonal tumor. These tumors start in the cerebellum. There are several different types of medulloblastomas, based on how the tumor cells look under a microscope, and on which gene mutations the cells have. Some types of medulloblastoma tend to have a better outlook than others, and doctors are now trying to determine how this might affect treatment.

Medulloblastomas can often be treated effectively and tend to have a better outlook than embryonal tumors in other parts of the brain.

Other, less common types of embryonal tumors include:

• Medulloepithelioma
• Atypical teratoid/rhabdoid tumor (ATRT)
• Embryonal tumor with multilayered rosettes

In the past, many embryonal tumors were referred to as primitive neuroectodermal tumors (PNETs).

Pineal tumors

Some types of tumors occur in the pineal gland (a small gland in the middle of the brain). The most common (and fastest growing) of these are called pineoblastomas. These tumors can be hard to treat.

Germ cell tumors, which are described below, can also start in the pineal gland.

Craniopharyngiomas

These slow-growing tumors start above the pituitary gland but below the brain itself. They account for about 4% of brain tumors in children. These tumors may press on the pituitary gland and the hypothalamus, causing hormone problems. Because craniopharyngiomas start very close to the optic nerves, they can also cause vision problems. This makes them hard to remove completely without damaging the child’s vision or hormone balance.

Mixed glial and neuronal tumors

Certain tumors that develop in children and young adults (and rarely in older adults) have both glial and neuronal cell components. They tend to have a fairly good outlook.

• Dysembryoplastic neuroepithelial tumors (DNETs) tend to be slow growing (grade II) tumors, and most can be cured by surgery alone.
• Ganglioglioma is a type of grade I tumor that has both mature neurons and glial cells. Most can be cured by surgery alone or surgery combined with radiation therapy.

Choroid plexus tumors

These rare tumors start in the choroid plexus, the area that makes cerebrospinal fluid (CSF) within the ventricles of the brain. Most are benign (choroid plexus papillomas) and can be cured by surgery. However, some are malignant (choroid plexus carcinomas).

Schwannomas (neurilemmomas)

These tumors start in Schwann cells that surround and insulate cranial nerves and other nerves. Schwannomas are usually benign . They often form near the cerebellum on the cranial nerve responsible for hearing and balance, in which case they are called vestibular schwannomas or acoustic neuromas. They may also develop on spinal nerves, just past the point where the nerve leaves the spinal cord. When this is the case, the tumor can press on the spinal cord, causing weakness, sensory loss, and bowel and bladder problems.

These tumors are rare in children. When schwannomas are found in a child, particularly if there are tumors on both sides of the head, it often means the child has an inherited tumor syndrome such as neurofibromatosis type 2. (See Risk Factors for Brain and Spinal Cord Tumors in Children.)

Other tumors that start in or near the brain

Meningiomas

These tumors begin in the meninges, the layers of tissue that surround the outer part of the brain and spinal cord. Meningiomas cause symptoms by pressing on the brain or spinal cord. They are much less common in children than in adults.

Meningiomas are almost always benign and are usually cured by surgery. Some, however, are located very close to vital structures in the brain and can’t be cured by surgery alone.

Meningiomas are often assigned a grade based on how the tumor cells look.

• Grade I meningiomas, which look most like normal cells, account for most meningiomas.
• Grade II (atypical) meningiomas look slightly more abnormal.
• Grade III (anaplastic or malignant) meningiomas, which look the most abnormal, make up only about 1% to 3% of meningiomas.

Higher-grade meningiomas are more likely to come back after treatment, and some grade III meningiomas can spread to other parts of the body.

Chordomas

These tumors start in the bone at the base of the skull or at the lower end of the spine. Chordomas don’t start in the central nervous system, but they can injure nearby parts of the brain or spinal cord by pressing on them. These tumors tend to come back if they are not removed completely, causing more damage. They usually do not spread to other organs. Chordomas are much more common in adults than in children. For more on these tumors, see Bone Cancer.

Germ cell tumors

These rare tumors develop from germ cells, which normally form egg cells in women and sperm cells in men. During normal development before birth, germ cells travel to the ovaries or testicles and develop into egg or sperm cells. But sometimes some germ cells don’t move where they should and end up in abnormal locations such as the brain. They may then develop into germ cell tumors, similar to those that can form in the ovaries or testicles.

Germ cell tumors of the nervous system usually occur in children, most often in the pineal gland or above the pituitary gland. These tumors can sometimes be diagnosed without a biopsy by measuring certain chemicals in the cerebrospinal fluid (CSF) or blood.

Types of germ cell tumors include:

• Germinomas (the most common type of CNS germ cell tumor)
• Choriocarcinomas
• Embryonal carcinomas
• Teratomas
• Yolk sac tumors (endodermal sinus tumors)

Neuroblastomas

These nerve cell tumors are the third most common cancer in children. But neuroblastomas rarely develop in the brain or spinal cord; most develop from nerve cells inside the abdomen or chest. This type of cancer is most common during early infancy. For more information, see Neuroblastoma.

Lymphomas

Lymphomas are cancers that start in cells called lymphocytes, which are white blood cells that are part of the immune system. Most lymphomas start in other parts of the body, but a small portion start in the central nervous system (CNS), and are called primary CNS lymphomas. These tumors are rare in children. For more on childhood lymphomas, see Non-Hodgkin Lymphoma in Children.

Pituitary tumors

Tumors that start in the pituitary gland are almost always benign (non-cancerous). But they can still cause problems if they grow large enough to press on nearby structures or if they make too much of any kind of hormone. These tumors are more common in teens than in younger children. For more information, see Pituitary Tumors.

Cancers that spread to the brain from other parts of the body

Sometimes tumors in the brain are found to have metastasized (spread) there from some other part of the body. Tumors that start in other organs and then spread to the brain are called metastatic or secondary brain tumors (as opposed to primary brain tumors, which start in the brain). This is important because metastatic and primary brain tumors are often treated differently.

In children, metastatic brain tumors are much less common than primary brain tumors. Childhood leukemias can sometimes spread to the CSF around the brain and spinal cord. When this happens, the cancer is still considered a leukemia (the cancer cells in the CSF are leukemia cells), so doctors use treatments directed at the leukemia. For more information, see Childhood Leukemia.