Types of Childhood Brain Tumors

Many different types of brain tumors occur in children, and the nomenclature can seem daunting. Many brain tumors are named for both the type of cell from which the tumor originated and the location of the tumor in the brain. Even the NCI PDQ states that the nomenclature of pediatric brain tumors is controversial and potentially confusing. Properly naming and classifying a tumor is important because proper treatment depends on proper diagnosis. "The pathologic classification of pediatric brain tumors is a specialized area that is evolving; review of the diagnostic tissue by a neuropathologist who has particular expertise in this area is strongly recommended.

Medulloblastomas arise from primitive neuroectodermal tissue, or PNET. PNET is a general term for a collection of many different brain tumors which arise from undeveloped brain cells. Medulloblastomas are usually located in the cerebellum and are fast growing and highly malignant. They frequently spread, invading other parts of the central nervous system via the spinal fluid. Medulloblastomas account for the largest percentage of pediatric brain cancers. It is more common in boys than girls and usually occurs between the ages of 2 and 6 (only 30% of medulloblastomas occur in adults) and frequently spreads.
Ependymomas arise from the cells that line the internal surfaces of the brain, thus, they are gliomas. The tumors arise from 'ependyma,' cells that line the fluid spaces of the brain and spinal cord. Ependymomas located in the cerebral hemispheres occur primarily in children and adolescents. Although these tumors are capable of malignant behavior, they are almost always benign.
Astrocytomas arise from brain cells which form part of the supportive system of the brain, in particular, cells called "astrocytes" for their star shaped appearance. This tumor are usually slow growing and many are considered curable. Astrocytomas are often cystic, in which case they are particularly easy to remove completely.
Optical nerve gliomas are slow growing tumors which form along the optic nerves. They usually occur in children under the age of 10. The common cell type is pilocytic astrocytoma.
Brain stem glioma, located in the brain stem, can be either slow or fast growing. Depending on the type of supporting tissue from which they arise, they can be either astrocytomas, anaplastic astrocytomas, glioblastoma multiforme, or a mixed tumor. In general, brain stem tumors are more common in children than they are in adults. Surgery is usually not possible in these tumors, and radiation and chemotherapy must be used instead.
Oligodendrogliomas are a slow growing tumor which arises from cells which make the myelin that insulates nerve fibers. They are located in the hemispheres of the brain, especially the frontal and temporal lobes, and in children are more common in the thalamus.
Gangliogliomas are usually slow growing, and rarely malignant. These tumors can be located anywhere in the brain, but are most often found in the temporal lobe. They arise from ganglia (a ganglion is a group of nerve cells). They occur most frequently in children and young adults.
Craniopharyngioma are benign (non-cancerous), congenital tumors. They are usually cystic and found primarily in children and adolescents.
Pineal Region Tumors are located in the pineal gland at the posterior portion of the third ventricle. The most common tumor of the pineal region is the germinoma. Germinomas (germ cell tumors) represent over one-third of the tumors in this region. Germinomas of the pineal region are most common in teenagers. Additional tumors found in this area include other embryonal type tumors, teratomas, astrocytomas, pineocytomas, and pineoblastomas.