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Most recently updated on April 10, 2013
Most childhood tumors (more than 60%) are located in the posterior fossa (the back compartment of the brain). This area is separated from the cerebral hemispheres by a tough membrane called the tentorium. The posterior fossa includes the cerebellum, the brainstem, and the fourth ventricle. Tumors in this area include medulloblastomas (also called primitive neuroectodermal tumors, or PNETs), cerebellar astrocytomas, brainstem gliomas, and ependymomas. Although less common, other rare types of tumors have also been observed in this area, such as rhabdoid tumors and ganglioglioma; these are not discussed in detail below.
The remaining 30% to 40% of brain tumors occur within one of the two cerebral hemispheres or in the spinal cord. Tumors of the hemispheres include astrocytomas, oligodendrogliomas, craniopharyngiomas, choroid plexus carcinomas, ependymomas, supratentorial PNETs, pineoblastomas, and germ cell tumors. The most common tumors of the spinal cord are astrocytomas and ependymomas.
Names of tumors can be confusing. One large family of tumors—comprising half of all pediatric tumors—are gliomas, meaning they arise from glial cells or the supporting cells of the nervous system. Glial cells consist of astrocytes, ependymal cells, and oligodendrocytes (myelin-forming cells). Some tumors take their names from these cells. For example, an astrocyte is a type of glial cell from which astrocytomas arise, so doctors may refer to the tumor as a glioma or as an astrocytoma. One term is simply more specific than the other. Tumors may also take their names from their location, such as the brainstem glioma.
The sudden influx of medical terminology into your life can be intimidating. Health care professionals are familiar with such terminology through years of training and experience. But these terms are new to you, so ask your child’s doctor to explain them. There are many types of brain tumors and many names for them—often even more than one name for the same tumor. The descriptions that follow include only the most common types of brain tumors found in children, divided into two broad groups according to their location.
Tumors of the Posterior Fossa
Medulloblastomas: Medulloblastomas (PNETs) are the most common malignant brain tumor in children (20% of all pediatric tumors) and usually occur in children between the ages of 4 and 10 years. Medulloblastomas occur more often in boys than in girls. These tumors typically arise in the middle of the cerebellum, interfering with the flow of CSF and causing hydrocephalus. A child may have headaches, vomit, or walk unsteadily. Sometimes there is pain at the back of the head. Medulloblastomas can spread to other parts of the brain through the CSF. Treatment is usually surgical removal, followed by radiation therapy of the entire head and spinal cord and/or chemotherapy.
Cerebellar Astrocytomas: Cerebellar astrocytomas are benign glial tumors of the cerebellum. They are the second most common childhood tumor (15% to 20% of all pediatric tumors). They can occur at any time in childhood or adolescence and have the same symptoms as medulloblastomas. Treatment is surgical removal, which is the cure in most cases if the tumor is totally removed. If the tumor has grown into the brainstem, radiation therapy or chemotherapy (depending on the child’s age) is sometimes needed.
Brainstem Gliomas: Approximately 10% to 15% of childhood brain tumors are brainstem gliomas, which most commonly affect children between the ages of 5 and 10 years. Because of their location, brainstem gliomas may cause sudden dramatic symptoms, such as double vision, clumsiness, difficulty swallowing, and weakness. These are often referred to as diffuse pontine gliomas. In these cases, surgery is not usually an option. Radiation therapy, with or without chemotherapy, is the preferred option. A small percentage of slow-growing tumors that cause slowly progressive symptoms can be treated surgically or with chemotherapy.
Ependymomas: Ependymomas make up 8% to 10% of pediatric tumors and occur at any time during childhood. They are a type of glioma involving cells lining the cerebral ventricles. Seventy percent of ependymomas develop in the posterior fossa. These tumors are not always distinguishable, on scans, from medulloblastomas. They cause similar symptoms, and hydrocephalus is often involved. Surgical removal of the tumor is the usual treatment of choice, followed by radiation therapy to the site of the resection.
Tumors of the Cerebral Hemispheres
Supratentorial Gliomas: About 30% of pediatric brain tumors are gliomas that grow in regions of the cerebral hemispheres. Treatment and prognosis depend on their exact location and how quickly they are growing. Some of the names for tumors in these areas are juvenile pilocytic astrocytoma, optic glioma or hypothalamic glioma (see below), oligodendroglioma, hemispheric astrocytoma, and ganglioglioma. Many of these tumors cause seizures. Surgical removal is the treatment of choice, unless the tumor is in an area that controls speech, movement, vision, or cognition. The tumor may be partially removed, with radiation therapy and/or chemotherapy as additional therapy.
Optic Pathway Gliomas: A small percentage (5%) of pediatric tumors are gliomas involving the optic nerves and the hypothalamus. These are usually slow-growing and can be treated successfully with surgery, radiation therapy, or chemotherapy. Because visual pathways and/or the hypothalamus are affected, children with these tumors often have vision and hormone problems.
Craniopharyngiomas: Craniopharyngiomas, which are nonglial growths, account for 5% of childhood brain tumors, usually causing growth failure because of their location near the pituitary gland. They often affect vision. Treatment is often controversial because complete surgical removal may be curative but can also cause memory, vision, behavioral, and hormonal problems. Partial surgical removal plus radiation therapy is an alternative. Children treated for these tumors usually need long-term follow-up care for visual and/or hormonal problems.
Germ Cell Tumors: A small percentage of childhood brain tumors arise in the pineal or suprasellar regions, above the pituitary gland. They are most often diagnosed around the time of puberty and are more likely to affect boys than girls. These tumors often respond favorably to chemotherapy and/or radiation therapy, following surgery.
Choroid Plexus Papillomas: The choroid plexus is located within the ventricles in the brain and produces CSF. Choroid plexus papillomas (benign) and choroid plexus carcinomas (malignant) account for 1% to 3% of pediatric brain tumors. These types of tumors usually arise in infants and often cause hydrocephalus. The treatment of choice is surgery and, if the tumor is malignant, chemotherapy, and/or radiation therapy.
Supratentorial PNETs/Pineoblastomas:Supratentorial PNETs and pineoblastomas account for approximately 5% of pediatric brain tumors. Their symptoms depend on location and proximity to the CSF spaces. Treatment involves maximal surgical resection, radiation therapy to the brain and spine, and chemotherapy.
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