Tumour types

Gliomas

Astrocytoma, Well-differentiated Astrocytoma, Anaplastic Astrocytoma, Glioblastoma Multiforme

Other Gliomas

Brain Stem Glioma, Ependymoma, Ganglioneuroma, Juvenile Pilocytic, Mixed Glioma, Oligodendroglioma, Optic Nerve Glioma

Non Gliomas

Chordoma, Craniopharyngioma, Medulloblastoma, Meningioma, Pineal Tumours, Pituitary Adenoma, Primitive Neuroectodermal Tumours (PNETs), Schwannoma, Vascular Tumours

Other Brain Related Conditions

CNS Lymphoma, Meningeal Carcinoma, Neurofibromatosis, Pseudotumour Cerebri, Tuberous Sclerosis

Gliomas

About half of all primary brain tumours and about one-fifth of all primary spinal cord tumours are gliomas - grow from glial cells. Within brain gliomas usually occur in the cerebral hemispheres but may also strike other areas, especially the optic nerve, the brain stem and the cerebellum (particularly among children). Gliomas are classified into several groups because there are several different kinds of glial cells.

· Astrocytoma

The most common type of glioma and also the most common type of brain tumour. Develop from star-shaped glial cells (astrocytes) and may occur anywhere in the CNS - brain, brain stem or spinal cord. Usually surgical treatment, radiation therapy and sometimes chemotherapy. Tumour grade determines treatment - the degree of anaplasia (pathology from biopsy). Anaplasia describes characteristic pattern in which tumour cells grow without form, structure or orientation to one another. An astrocytoma is assigned a grade - according to its degree of anaplasia. This reflects its potential for growth. Most rapid growing astrocytomas have greatest degree of anaplasia, are the most anaplastic and are the most malignant. Only astrocytomas are referred to by grade - other types of tumours are not.

Low-grade gliomas (general term for slow growing astrocytoma) to high-grade (the more rapid growing anaplastic astrocytoma). Within this are four subgroups according to increasing degree of anaplasia. Low-grade gliomas include the mildly anaplastic astrocytoma and the moderately anaplastic astrocytoma. High-grade gliomas include highly anaplastic astrocytoma and the glioblastoma multiforme. The WHO grades on a scale of 1-4, from least to most aggressive tumour types. There is the Kernohan-Sayre system of classification and that of the National Institute of Neurological Disorders and Stroke. This classifies astrocytomas into three grades:

· Well-differentiated astrocytomas

Low-grade (grade I) astrocytomas. Relatively normal and less malignant than other two grades. Grow slowly and may sometimes be completely removed by surgery. Can be life-threatening if they are inaccessible.

· Anaplastic astrocytomas

Mid-grade (Grade II) astrocytomas. May be more rapidly growing than the well-differentiated type and contain cells with some malignant traits.

· Glioblastoma multiforme

High-grade (grade III) astrocytomas grow rapidly, invade nearby tissue and contain cells that are very malignant. Among most common and devastating brain tumours that strike adults.

Other Gliomas

· Brain Stem Glioma

Accounts for 20% of childhood tumours (mostly between 3 and 10 years) and just short of 5% adult tumours. They range from very low-grade astrocytomas (juvenile pilocytic astrocytoma) to the rapidly anaplastic glioblastoma multiforme. Named by location at the base of brain rather than cells they contain. Symptoms of this tumour include nausea, headache, speech or balance abnormalities, difficulty with swallowing and weakness or numbness of the arms or legs. Symptoms can develop insidiously and as much as a year can pass before they are recognised. Can also develop abruptly - relates to more rapidly growing tumours. Not usual to surgically treat these brain stem gliomas because of vulnerable location. Tumours in this region are uniformly dangerous but low-grade tumours may have very long periods of remission.

· Ependymoma

About 5% of adult intracranial gliomas and 10% childhood tumours of CNS. Peaks around 5 years of age and again at 34. About 85% are benign. Develop from cells that line both the hollow cavities of brain and canal containing spinal cord, but usually arise from 4th ventricle, situated at lower back portion of brain. May produce headache, vomiting and obstruction of cerebrospinal fluid. Can cause hydrocephalus. Ependymomas are generally localised and slow growing low-grade tumours though some are anaplastic and malignant. Most are not anaplastic. The anaplastic (malignant) varieties of this tumour (malignant ependymoma and ependymoblastoma) treated like medulloblastoma but prognosis much less favourable. Ependymoblastomas in infants and children under 5 may spread through cerebrospinal fluid. The subependymoma (variant of ependymoma) apt to rise in the 4th ventricle but may occur in septum pellucidum and the cervical spinal cord. Usually affects over 40s and more often men than women. The subependymal giant-cell astrocytoma (giant-cell glioma) typically associated with tuberous sclerosis but can occur independent of that condition. This tumour tends to cause obstruction when large (arising in the walls of the lateral ventricles over the basal ganglia). Sharply defined tumour and generally benign.

· Ganglioneuroma

Rarest form of glioma. Tumours contain both glial cells and mature neurons. Relatively slow growing and may occur in brain or spinal cord. Usually surgically treated.

· Juvenile Pilocytic

JPA (Juvenile Pilocytic Astrocytoma) common childhood tumour sometimes in adults. Can arise in any area of brain but mostly in cerebellum and is surrounded by capsule-like cyst. Headache, nausea, vomiting, ataxia (muscle co-ordination) are symptoms. Low-grade glioma. Very slow growing often surgical cure. JPA in optic chiasm (for example) impossible to remove totally because of location.

· Mixed Glioma

Composed of two or more types of glioma tumour cells. Usually astrocytes and other glial cell types. Mixed tumour composed of oligodendroglioma and anaplastic astrocytoma treated as a pure anaplastic astrocytoma. Treatment is for the most malignant tumour cell found in the mix. If the oligodendroglioma is the more anaplastic of the two cell types, treatment directed towards that component. Prognosis of mixed gliomas decided according to the most anaplastic part of the mixed tumour.

· Oligodendroglioma

Develop from glial cells called oligodendroglia (about 5% of all gliomas). Mostly young adults and within the brain’s cerebral hemispheres. Relatively rare and slow growing. There is a malignant form of the oligodendroglioma and a mixed malignant astrocytoma-oligodendroglioma both treated much like the glioblastoma multiforme.

· Optic Nerve Glioma

Found on or near the nerves that travel between eye and brain vision centres. Common in people with neurofibromatosis.

Non Gliomas

· Chordoma

Common in 20s and 30s and develop from remnants of flexible spine-like structures that form and dissolve early in foetal development and is later replaced by the spinal cord. Often slow-growing tumours can metastasise or recur after treatment. Metastasise - movement of diseased malignant tissue to another area.

· Craniopharyngioma

Region of optic nerve and hypothalamus - structure near pituitary gland. Like chordomas develop from left over cells from early foetal development. Vision and hormonal problems, slowing child's growth and causing poor regulation of water balance. Benign craniopharyngioma is a tumour that usually affects infants and children but sometimes adults. Removed with minimal brain damage (not so 10 years ago) by microsurgery.

· Mebulloblastoma

Most common PNET- primitive neuroectodermal tumour - about 25% of all childhood brain tumours. More in children than adults. Medulloblastoma most often arises in cerebellum (lower back part of brain) and causes symptoms of headache, nausea, vomiting and ataxia. Unlike other primary brain tumours, medulloblastoma has a tendency to spread outside nervous system if untreated to lymph nodes, bone marrow and lungs or other parts of body. Fast-growing tumours.

· Meningioma

Common brain tumour originating from meninges, thin membranes or linings that cover the brain and spinal cord. Although forms in the meninges may extend into the substance of the brain. Account for 15% of all brain tumours and about 25% of all primary spinal cord tumours. Affects all ages but most common in 40s. Usually slow growing and generally do not invade surrounding normal tissue. Rarely spread to other parts of CNS or body. Most never become malignant. Can rarely become malignant.

· Pineal Tumours

Arise in pineal gland region (small structure deep in brain). Account for 1% of brain tumours but make up 3-8% of intracranial child tumours. At least 17 different types of tumour may occur in this area many of which are benign. Three most common are gliomas, germ cell tumours and pineal cell tumours. Histological diagnosis essential from pathology to be exact in planning therapy. Benign pineal tumours can be removed surgically. The germinoma - most common malignant tumour in this area - cured in 90% of patients.

· Pituitary Adenoma

Pituitary gland is small oval structure located at brain base in centre of head, behind eyes and optic nerve. About pea sized but very important. Secretes several chemical messengers (hormones) to help control body's other glands and regulate growth, metabolism, maturation and other essential body processes. Tiny tumour located just next to the gland. These pituitary adenomas account for about 10% of brain tumours. Two groups. Secreting and non-secreting.

Secreting tumours release unusually high levels of pituitary hormones triggering a constellation of symptoms. Usually much smaller than the gland when they begin to cause symptoms and the symptoms depend on the tumour's size and kind of hormone secreted. Prolactin-secreting adenomas affect sexual characteristics and cause impotence in men. Prolactin secreted from cells of anterior lobe and is a lactogenic hormone in women. It stimulates the developed mammary gland to secrete milk. Adenomas secreting growth hormone cause acromegaly (abnormal growth, enlarged facial features, hands and feet) and gigantism (excessive size and stature).

The less common adrenocorticotropic hormone-secreting adenoma causes Cushing's disease (concurrence of obesity, hairiness, linear atrophy of skin, loss of sexual function and curvature of spine). Some adenomas secrete a combination of these and other hormones and some secrete none. Almost all adenomas are benign but slow expansion compresses normal structure that surround it. Suppresses normal pituitary function sometimes causing headaches or vision problems. Pituitary adenomas rarely metastasise or spread to other areas of body. Microsurgically removed very successfully for the majority of patients.

· Primitive Neuroectodermal Tumours

These PNETs usually affect children and young adults. Believed to spring from primitive cells left over from early development of nervous system. Very malignant and grow rapidly spreading easily within brain and spinal cord. Rare cases cause cancer outside CNS. Medulloblastomas most common PNET. More rare are neuroblastomas, pineoblastomas, medulloepitheliomas, ependymoblastomas and polar spongioblastomas. These malignant cells often spread in scattered, patchy pattern - so these PNETs difficult to remove by surgery.

· Schwannoma

Arise from cells that form protective sheath around body's nerve fibres. Usually benign and surgically removed when possible. One of the more common forms of schwannoma affect 8th cranial (acoustic) nerve important for balance and hearing. Also known as vestibular schwannomas or acoustic neuromas grow on one or both sides of brain.

· Vascular Tumours

Rare non-cancerous tumours arise from blood vessels of brain and spinal cord. Most common vascular tumour is the haemangioblastoma linked in small number of people to a genetic disorder (von Hippel-Lindau disease). Not usually spread and typically removed surgically.

Other Brain-Related Conditions CNS Lymphoma

Form of cancer occurring when cells from body's immune system grow out of control. Affects small number of otherwise healthy people and a larger fraction of those who have an impaired immune system, whether from organ transplants, infection with the AIDS virus or other causes. CNS lymphoma can be primary or secondary. Usually treated with radiation. If lymphoma affects meninges, chemotherapy directly into cerebrospinal fluid. Often recur.

· Meningeal Carcinomatosis

Strikes when individual cells from cancer outside the CNS enter cerebrospinal fluid and grow like seeds. Cells travel with fluid and can form colonies or small tumours in many places, including roots of nerves, surface of brain, brain stem and spinal cord. Usually radiation therapy which can sometimes slow growth of cells.

· Neurofibromatosis

Genetic disorder can cause tumours in various parts of nervous system. Type 2 causes multiple central nervous system tumours (neurofibromas, bilateral vestibular schwannomas and increased risk of optic nerve gliomas). Surgical treatment usually to remove tumours causing symptoms. More common form of this disorder (neurofibromatosis Type 1) usually benign tumours outside the CNS.

· Pseudotumour Cerebri

Condition easily confused with brain tumour because symptoms closely mimic those of brain tumours. possibly because of buildup of cerebrospinal fluid placing pressure on brain. Pseudotumour cerebri is diagnosed by ruling out all other possible causes for symptoms and confirming by lumbar puncture to release cerebrospinal fluid, special drugs to correct fluid levels, shunts to drain fluid or, in severe cases, surgery to relieve pressure on brain.

· Tuberous Sclerosis

Genetic disorder causes numerous neurological and physical symptoms, including tumours of the kidneys, eyes, and CNS. About half of patients who have tuberous sclerosis develop subependymal giant-cell astrocytoma.

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