Brain tumor

A brain tumor is any intracranial mass created by an abnormal and uncontrolled growth of cells either normally found in the brain itself: neurons, glial cells (astrocytes, oligodendrocytes, ependymal cells), lymphatic tissue, blood vessels), in the cranial nerves (myelin producing cells Schwann cells), in the brain envelopes (meninges), skull, pituitary and pineal gland, or spread from cancers primarily located in other organs (metastatic tumors).

Classification

In contrast to tumors originating elsewhere in the body, differentiating primary "brain tumors"—these are the true brain tumors, arising exclusively from cells normally present in the brain itself—into benign and malignant is of relative and limited clinical value, since even histologically-benign tumors grow by infiltration of healthy brain tissue and, in time, tend to transform into malignant forms (anaplastic degeneration).

Related Topics:
Benign - Malignant - Anaplastic degeneration

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True benign intracranial tumors arise mainly from the meninges (meningiomas; about 95% are benign), pituitary gland (pituitary adenomas) and the myelin sheath of cranial nerves (neuromas or Schwanomas, e.g. acoustic neuroma).

Related Topics:
Meninge - Meningiomas - Pituitary gland - Pituitary adenoma - Myelin sheath - Cranial nerve - Neuromas - Schwanomas - Acoustic neuroma

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Most primary brain tumors (gliomas) originate from glia: astrocytes (astrocytomas), oligodendrocytes (oligondedrogliomas). There are also mixed forms, with both an astrocytic and an oligodendroglial cell component. These are called mixed gliomas or oligoastrocytomas.

Related Topics:
Glioma - Glia - Astrocytomas - Oligondedrogliomas - Mixed gliomas - Oligoastrocytomas

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Additionally, mixed glio-neuronal tumors (tumors displaying a neuronal, as well as a glial component, e.g. gangliogliomas, disembryoplastic neuroepithelial tumors) and tumors originating from neuronal cells (e.g. gangliocytoma, central gangliocytoma) can also be encountered.

Related Topics:
Ganglioglioma - Disembryoplastic neuroepithelial tumor - Gangliocytoma - Central gangliocytoma

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Other varieties of primary brain tumors include: primitive neuroectodermal tumors (PNET, e.g. medulloblastoma, medulloepithelioma, neuroblastoma, retinoblastoma, ependymoblastoma), tumors of the pineal parenchyma (e.g. pineocytoma, pineoblastoma), ependymal cell tumors, choroid plexus tumors, neuroepithelial tumors of uncertain origin (e.g. gliomatosis cerebri, astroblastoma), etc.

Related Topics:
Primitive neuroectodermal tumor - Medulloblastoma - Medulloepithelioma - Neuroblastoma - Retinoblastoma - Ependymoblastoma - Pineal - Parenchyma - Pineocytoma - Pineoblastoma - Ependyma - Choroid plexus - Gliomatosis cerebri - Astroblastoma

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From a histological perspective, astrocytomas, oligondedrogliomas, and oligoastrocytomas may be benign or malignant. Glioblastoma multiforme represents the most aggressive variety of malignant glioma. At the opposite end of the spectrum, there are so-called pilocytic astrocytomas, a distinct variety of astrocytic tumors. The majority of them are located in the posterior cranial fossa, affect mainly children and young adults, and have a clinically favorable course and prognosis.

Related Topics:
Glioblastoma multiforme - Pilocytic astrocytoma - Posterior cranial fossa

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In contrast to other types of cancer, primary brain tumors rarely metastasize, and in this rare event, the tumor cells spread within the skull and spinal canal through the cerebrospinal fluid, rather than via bloodstream to other organs.

Related Topics:
Cancer - Skull - Spinal canal - Cerebrospinal fluid

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There are various classification systems currently in use for primary brain tumors, the most common being the World Health Organization (WHO) brain tumor classification, introduced in 1993.

Related Topics:
World Health Organization - 1993

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Secondary or metastatic brain tumors originate from malignant tumors (cancers) located primarily in other organs. Their incidence is higher than that of primary brain tumors. The most frequent types of metastatic brain tumors originate in the lung, skin (malignant melanoma), kidney (hypernephroma), breast (breast carcinoma), and colon (colon carcinoma). These tumor cells reach the brain via the blood-stream.

Related Topics:
Metastatic brain tumors - Malignant tumors - Lung - Skin - Malignant melanoma - Kidney - Hypernephroma - Breast - Breast carcinoma - Colon - Colon carcinoma

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Some non-tumoral lesions can mimic tumors of the central nervous system. These include tuberculosis of the brain and cerebral abscess.

Related Topics:
Central nervous system - Tuberculosis - Cerebral abscess

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