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Childhood brain or spinal cord tumours are divided into many different categories. Each category is based on the type of cell the tumour started from, the grade (how fast the tumour grows) and the tumour's location.
Gliomas begin in the supportive tissues (glial cells) of the brain. Gliomas in children usually occur in the cerebellum (lower part of the brain). They can also occur in the cerebrum (upper part of the brain) or brain stem (front of the cerebellum). Tumours that fall under the category of gliomas include:
Astrocytomas develop in the astrocytes which are star-shaped supporting cells that carry food to the nerve cells. Approximately 45% of all childhood brain tumours will be astrocytomas.
Brain stem gliomas are astrocytomas that start in the brain stem.
Oligodendrogliomas develop from glial cells called oligodendrocytes. Oligodendrocytes make the myelin sheath that insulates the nerve cells and helps transmit messages in the white matter of the brain.
Optic nerve gliomas develop anywhere along the nerves that carry messages from the eye. Hypothalamic gliomas occur in the hypothalamus.
Ependymomas start in the lining (ependyma) of the ventricles and the cavity in the centre of the spinal cord.
Choroid plexus tumours start in the tissue of the choroid plexus, which is located in each of the ventricles. There are 2 types:
Neuroectodermal tissue normally grows and matures into nerve cells. Primitive neuroectodermal tumours start from neuroectodermal cells that do not develop from when the fetus (baby) was growing in the uterus (womb).
Medulloblastomas are the most common type of PNET and the names are used interchangeably in some classification systems.
Tumours that look similar to medulloblastomas under the microscope, but occur above the tentorium in the cerebrum, are called supratentorial primitive neuroectodermal tumours (SPNETs).
Other types of PNETs make up less than 5% of all childhood brain tumours. They are found throughout the brain and tend to spread through the CSF. These tumours include:
Pineal tumours develop in the pineal gland.
Ependymoblastomas are fast-growing tumours that start in the ventricles where cerebrospinal fluid is made. They tend to occur in children rather than adults, but are rare.
Cerebral neuroblastomas tend to develop in the frontal (front) and temporal (side) lobes of the cerebrum. These tumours may spread throughout the subarachnoid space. They occur most often in children up to the age of 5 years.
Germ cell tumours develop from germ cells that normally develop into eggs in women and sperm in men. During normal development, germ cells travel to the ovaries and mature into egg, or to the testicles and mature into sperm. Sometimes a few germ cells do not move to the ovaries or testicles as they should and end up in abnormal places such as the brain. In some cases, these cells develop into a tumour, usually in the centre of the brain near the pineal gland.
There are 3 types of germ cell tumours:
Germ cell tumours can be benign or malignant. They have the potential to spread to other parts of the brain and spinal cord.
Pituitary tumours develop in the pituitary gland. The pituitary gland produces hormones that control growth and physical and sexual development. These hormones also affect other glands in the body, such as the thyroid and adrenal glands. Pituitary tumours are divided into 3 groups:
For more information about pituitary tumours go to pituitary gland cancer.
Craniopharyngiomas are slow-growing tumours that start in the centre part of the brain, usually near the pituitary gland.
Dysembryoplastic neuroepithelial tumours are slow-growing tumours that often develop in the temporal lobe or frontal lobe of the cerebrum. Under the microscope, they look very much like a malignant oligodendroglioma, but behave very differently and so are treated differently.
Gangliogliomas are usually slow-growing tumours that can occur anywhere in the brain. They make up approximately 10% of all primary brain tumours in children. They contain a mixture of mature neurons (nerve cells) and glial cells (supportive cells). Gangliogliomas are rarely malignant and usually do not spread.
Schwannomas start in Schwann cells that surround and insulate cranial nerves. They often develop in the part of the eighth cranial nerve (the vestibular branch) which controls balance, and are sometimes called vestibular schwannomas. Although these tumours develop in the part of the nerve that controls balance, hearing loss is usually the first sign associated with the tumour. Schwannomas are usually slow-growing and don't occur very often in children.
Meningiomas are slow-growing and occur in the outermost covering in the brain (meninges). Less commonly, they will develop in the ventricles. Meningiomas rarely occur in children.
Atypical teratoid/rhabdoid tumours are rare, high-grade tumours that can develop anywhere in the brain. These tumours tend to be fast-growing and often spread through the central nervous system. These usually occur in children less than 3 years of age.
Spinal cord tumours are rare in children and only make up a small percentage of all childhood central nervous system tumours. Most are slow-growing.
Tumours that develop in the brain can also occur in the spinal cord. The most common types include:
Spinal cord tumours can be either intrinsic or extrinsic.
Some brain tumours begin elsewhere in the body and spread to the central nervous system. This is called metastases. This type of spread is rarely seen in children. The types of childhood cancer that could spread to the brain or spinal cord include kidney tumours, leukemia or lymphoma.
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