SUPPORT CANADIANS LIVING WITH CANCER
Types of childhood brain and spinal cord tumours
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.
- Cerebellar astrocytomas develop in the cerebellum and account for 10% – 20% of childhood central nervous system (CNS) tumours. They occur most commonly during the first 10 years of life.
- Pilocytic astrocytomas are generally low-grade (Grade 1) tumours, which means they are slow growing, may be surrounded by a capsule and usually do not spread.
- Fibrillary or diffuse (infiltrating) astrocytomas are slightly higher grade (Grade 2). They are not as common as low-grade pilocytic astrocytomas.
- Cerebral astrocytomas develop in the cerebrum. They can vary from low grade to high grade.
- High-grade tumours, such as anaplastic astrocytoma (a Grade 3 astrocytoma) or glioblastoma multiforme (a Grade 4 astrocytoma), will spread by growing into surrounding brain tissue.
Brain stem gliomas
Brain stem gliomas are astrocytomas that start in the brain stem.
- They account for 10% – 25% of all childhood brain tumours. They occur most often in children between the ages of 5 and 10 years.
- Brain stem gliomas can be low grade or high grade.
- The majority of childhood brain stem tumours are diffuse intrinsic pontine gliomas (DIPG). These are high-grade tumours that develop in the pons – a part of the brain stem deep within the brain. These tumours often involve surrounding tissue. Because of this and their location, DIPGs may be biopsied, but cannot be removed and are difficult to treat.
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.
- Oligodendrogliomas account for less than 5% of all childhood brain tumours.
- Most oligodendrogliomas tend to be low grade and less aggressive than other types of gliomas.
- They usually develop in the frontal lobes of the cerebrum.
Optic nerve and hypothalamic gliomas
Optic nerve gliomas develop anywhere along the nerves that carry messages from the eye. Hypothalamic gliomas occur in the hypothalamus.
- These tumours account for less than 5% of all childhood brain tumours. More than 75% of these tumours occur during the first 10 years of life and most are diagnosed in children under the age of 5.
- These are usually low-grade, slow-growing tumours.
Ependymomas start in the lining (ependyma) of the ventricles and the cavity in the centre of the spinal cord.
- Ependymomas account for 5%–10% of childhood brain tumours. They occur most commonly in children under the age of 5.
- Most ependymomas start in the back of the brain (posterior fossa), in or around the fourth ventricle. They can also occur in other areas of the brain and occasionally in the spinal cord.
- Ependymomas can cause a buildup of cerebrospinal fluid (CSF) in the brain (hydrocephalus) by blocking the flow of CSF which is made in the ventricles.
Choroid plexus tumours
Choroid plexus tumours start in the tissue of the choroid plexus, which is located in each of the ventricles. There are 2 types:
- Choroid plexus papilloma is a slow-growing tumour that doesn’t usually spread, but may block the flow of CSF. Most choroid plexus tumours are papillomas.
- Choroid plexus carcinoma is a fast-growing tumour that is more likely to spread to other parts of the brain and spinal cord. This tumour is sometimes called an anaplastic choroid plexus papilloma.
- Both choroid plexus papillomas and carcinomas can cause hydrocephalus.
Primitive neuroectodermal tumours (PNET)
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.
- This type of tumour accounts for 20%–40% of brain tumours in children under the age of 15. They occur twice as often in boys than in girls and most frequently occur between the ages of 4 and 8.
- Medulloblastomas usually develop in the posterior fossa. They can spread through the CSF to other parts of the brain and spinal cord.
- Of all the primary CNS tumours, medulloblastomas have the greatest potential to spread outside of the nervous system. The bone marrow, lymph nodes, liver, bones and lungs are common sites of spread.
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.
- Pineoblastomas are tumours that develop from primitive (very immature) cells. They are fast growing and can spread to organs outside of the brain.
- Pineocytomas are slower-growing tumours than pineoblastomas.
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
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:
- germinoma – most common type of germ cell tumour
- non-germinomatous germ cell tumour – also known as a secreting germ cell tumour
- Subtypes include choriocarcinoma, embryonal cell carcinoma and mixed tumour.
- teratoma – non-germinoma, non-secreting tumour; may be benign or malignant
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:
- benign pituitary adenomas
- These tumours are not cancerous. They grow slowly and do not usually spread to other parts of the brain.
- Types of pituitary adenomas include:
- prolactin secreting adenoma (prolactinoma)
- growth hormone (GH) secreting adenoma
- adrenocorticotropic hormone (ACTH) secreting adenoma
- thyroid-stimulating hormone (TSH) adenoma
- invasive pituitary adenomas
- These tumours are not cancerous but they can invade nearby tissues of the skull or the sinus cavity below the pituitary gland.
- pituitary carcinoma
- These are rare cancerous tumours. They can spread to other areas of the brain and spinal cord or outside of the central nervous system.
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.
- These tumours may grow and involve the hypothalamus, optic nerve pathways and third ventricle.
- Craniopharyngiomas are often made up of solid parts that contain calcium and cysts that contain fluid.
Mixed glial and neuronal tumours
Dysembryoplastic neuroepithelial tumours (DNET)
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 tumour
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.
- Intrinsic tumours develop within the spinal cord and stay within the spinal cord.
- Extrinsic tumours form on the outside of the spinal cord and put pressure on the cord as they grow.
- They can develop in the meninges (meningiomas).
- They can also grow on the nerves coming out of the spinal cord. These tumours are known as either neurofibromas or schwannomas.
- Extrinsic tumours can also be caused by cancer cells that have spread from tumours elsewhere in the body (metastases).
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.