Glioma

Gliomas are tumors that arise from the supportive tissue of the brain, the glial cells. There are three types of glial cells that can cause tumors. Astrocytes can produce astrocytomas (including glioblastomas), oligodendrocytes can produce oligodendrogliomas and ependymal cells can produce ependymomas. Tumors arising from a mixture of these different cells are called mixed gliomas (e.g. oligoastrocytoma). [3]

figure: Glial cells. Astrocytes, oligodendrocytes and ependymal cells [1]

Astrocytoma

Astrocytomas are tumors that arise from astrocytes (image on the left). Astrocytes make up the supportive and protecting tissue of the brain and also help to process information. They are the most abundant cells in the brain.

As astrocytes are practically omnipresent in the brain, astrocytomas can appear in various parts (including cerebellum, cerebrum, central areas of the brain, brainstem and spinal cord).

Astrocytomas can be graded from I to IV. While low-grade astrocytomas are usually localized and grow slowly and high-grade astrocytomas show a rapid growth. Grade IV astrocytoma is also called glioblastoma. Glioblastoma is the most common high-grade primary brain tumor in adults. [1,3]

Oligodendroglioma

Oligodendrogliomas develop from a type of glial cell known as an oligodendrocyte (image on the left). They usually grow slowly and don't spread. They can be of grade II or III.

They are commonly found in the frontal and temporal lobes, however they can be located anywhere within the cerebral hemisphere. Oligodendrogliomas can be present for years before they are diagnosed.

The shape of oligodendrogliomas reminds of a fried egg, potentially with “short arms”. They are generally soft and grayish-pink. [1][3]

Ependymoma

Ependymomas are tumors arising from ependymal cells (image on the left). Ependymal cells line the ventricles of the brain and the center of the spinal cord. The most common tumor type has grade II, but grading ranges from I to III.

The various types of ependymomas appear in different locations within the brain and spinal column (lower part of the spinal column, along, within or next to the ventricular system, ...).

Ependymomas are soft, grayish or red tumors, that tend to appear in kids under the age of 3 (nearly half of ependymoma diagnoses). [3][7]

Meningioma

Meningiomas are often benign tumors that develop in the meninges (layers beneath the bone, coverings of the brain and spinal cord). The majority of meningiomas are low-grade, but they represent about one-third of all primary brain tumors. Grading can range from I to III. Meningiomas occur most frequently in middle-aged women and older people. [1][3]

Medulloblastoma

Medulloblastoma is the most common type of embryonal tumors, since it arises from embryonal cells at the earliest stage of their development. Medulloblastoma is a fast-growing, high-grade tumor that is always located in the cerebellum.

It doesn't tend to spread to other areas of the body and is relatively rare. Less than 2% of all primary brain tumors and 18% of all pediatric brain tumors are medulloblastomas.

Medulloblastomas occur more often in men than in women, but more than 70% of all pediatric medulloblastomas appear in children under an age of 10. [3]

CNS Lymphoma

Lymphoma is a cancer that arises from the cells of the lymphatic system. It is caused by the uncontrolled growth of the lymph cells (a type of white blood cell). It does not only appear in people with improperly functioning immune systems, but also in people with healthy immune systems.

CNS Lymphomas represent between 2% and 3% of all primary brain tumors. They mostly occur in the cerebral hemisphere, but may also involve the ventricular system, eyes or spinal cord. They are likely to spread throughout the central nervous system. [1][3]

Others

Choroid plexus

benign or malignant, arises from brain tissue called choroid plexus, spreads widely via CSF, mostly in children [3]

Craniopharyngioma

benign, arises from small nests of cells near the pituitary stalk [3]

Cyst

tumor-like sphere filled with fluid, blood, tissue, or tumor cells; not truly a brain tumor as it does not arise from brain tissue [3]

Lipoma

rare, benign, composed of fatty tissue [3]

Neurofibroma

tumor of the nerve fibers, characterized by skin abnormalities and nervous system tumors [3]

Pineal tumors

arise from cells in the pineal gland, rarely spreads; pineal gland is involved in the secretion of specific hormones [3]

Pituitary tumors

arise from the pituitary gland (adenomas: benign, slow-growing, represent about 10% of primary brain tumors; carcinomas: rare, malignant); pituitary gland is involved in the production of several essential hormones [3]

PNET (primitive neuroectodermal tumor)

appears identical to medulloblastoma, but occurs primarily in the cerebrum, contains underdeveloped brain cells, highly malignant, tends to result in large tumors, spreads, most often occurs in very young children [3]

Schwannoma

tumor of the acoustic nerve, benign, very slow-growing, located between cerebellum and pons in the back of the skull, about 8% of all primary brain tumors [3]