Brain tumor classification

Brain tumor Microchapters
Patient Information
Overview
Classification Adult brain tumors Glioblastoma multiforme Oligodendroglioma Meningioma Hemangioblastoma Pituitary adenoma Schwannoma Primary CNS lymphoma Childhood brain tumors Pilocytic astrocytoma Medulloblastoma Ependymoma Craniopharyngioma Pinealoma Metastasis Lung cancer Breast cancer Melanoma Gastrointestinal tract cancer Renal cell carcinoma Osteoblastoma Head and neck cancer Neuroblastoma Lymphoma Prostate cancer
Causes
Differentiating Brain Tumor from other Diseases

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Sujit Routray, M.D. [2]

Overview

Brain tumors can be classified into two main categories: primary and secondary tumors. Primary tumors originate in astrocytes, oligodendrocytes and ependymal cells. Secondary tumors originate in malignant cancers located primarily in other organs.

Classification

Primary tumors

Tumors occurring in the brain include:

• Astrocytoma
• Pilocytic astrocytoma
• Dysembryoplastic neuroepithelial tumor
• Oligodendrogliomas
• Ependymoma
• Glioblastoma multiforme
• Mixed gliomas
• Oligoastrocytomas
• Medulloblastoma
• Retinoblastoma
• Neuroblastoma
• Germinoma
• Teratoma

Most primary brain tumors originate from glia (gliomas) such as astrocytes (astrocytomas), oligodendrocytes (oligodendrogliomas), or ependymal cells (ependymoma). There are also mixed forms, with both an astrocytic and an oligodendroglial cell component. These are called mixed gliomas or oligoastrocytomas. Plus, 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.

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.

Secondary tumors and non-tumor lesions

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-

• lung cancer
• skin cancer
• malignant melanoma
• hypernephroma)
• breast cancer
• colon carcinoma)
  • These tumor cells reach the brain via the blood-stream.

Some non-tumoral masses and lesions can mimic tumors of the central nervous system. These include-

• tuberculosis of the brain
• cerebral abscess (commonly in toxoplasmosis)
• hamartomas (for example, in tuberous sclerosis)
• von Recklinghausen neurofibromatosis

Specific tumor types

Brain tumors are classified depending on:

• Location of the tumor
• Type of tissue involved
• Whether they are noncancerous (benign) or cancerous (malignant)
• Other factors

Sometimes, tumors that start out less aggressive can change their biologic behavior and become more aggressive.

Tumors can occur at any age, but many types are most common in a certain age group. In adults, gliomas and meningiomas are the most common.

Gliomas come from glial cells such as astrocytes, oligodendrocytes, and ependymal cells. Gliomas are divided into three types:

• Astrocytic tumors include astrocytomas (can be noncancerous), anaplastic astrocytomas, and glioblastomas.
• Oligodendroglial tumors. Some primary brain tumors are made up of both astrocytic and oligodendrocytic tumors. These are called mixed gliomas.
• Glioblastomas are the most aggressive type of primary brain tumor.

Meningiomas and schwannomas are two other types of brain tumors. These tumors:

• Occur most often between ages 40 and 70.
• Are usually noncancerous, but can still cause serious complications and death from their size or location. Some are cancerous and aggressive.

Other primary brain tumors in adults are rare. These include:

• Ependymomas
• Craniopharyngiomas
• Pituitary tumors
• Primary (central nervous system - CNS) lymphoma
• Pineal gland tumors
• Primary germ cell tumors of the brain

References

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