What Are the Main Types of Brain Tumors?

Brain tumors are categorized according to their brain tissue origin and how fast they grow. Fast-growing brain tumors are known as high-grade tumors, while slow-growing ones are known as low-grade tumors. Below are some of the most known brain tumors:

• Ependymoma
• Meningioma
• Astrocytoma
• Medulloblastoma
• Craniopharyngioma
• Oligodendroglioma
• Gliomas
• Brainstem Glioma
• Pituitary Adenoma
• Schwannoma
• Germ Cell Tumor
• Primitive Neuroectodermal Tumor
• Primary Central Nervous System Lymphoma
• Mixed Glioma
• Optic Nerve Glioma
• Chordoma
• Diffuse Astrocytomas
• Hemangioblastoma

1. What Is Ependymoma?

Ependymoma is a tumor that originates from ependymal cells which together form the ependyma.

The ependyma is a type of brain ciliated epithelium, known as neuroepithelium, which forms a thin membrane lining the brain cavities (ventricles) and the central canal of the spinal cord.

Ependymoma is caused by mutations in genes that control the growth of ependymal cells [1]. They are categorized as slow-growing (Low Grade which includes Grade I and Grade II) or fast-growing (High grade or Grade III) [2].

In the United States, about 1096 people are diagnosed with ependymoma each year with 13294 people living with this tumor [2].

2. What Is Meningioma?

Meningioma is a common type of brain tumor that originates from the membranes that cover the brain and spinal cord and is known as meninges.

The causes of meningioma are not well-known; however, mutations in genes that control the growth of the cells within the membranes of the meninges may be involved [3].

Meningioma is classified as low grade or slow-growing (Grade I; the most common), mid-grade or atypical meningiomas (Grade II), and fast-growing or anaplastic meningiomas (Grade III) [4].

In the United States, about 371 people are diagnosed with meningioma each year with 2692 people living with this type of tumor [4].

3. What Is Astrocytoma?

Astrocytoma is a brain tumor that originates from a type of brain cells, known as astrocytes. Astrocytes and oligodendrocytes (another type of brain cell) are also known as glial cells.

Astrocytes are star-shaped cells involved in supporting nerve cells (neurons) by providing nutrients, repairing nervous tissue following injury or infection, and regulating blood flow in the brain.

The causes of astrocytoma are not known but may involve genetic and immunologic anomalies.

Astrocytoma is categorized into the following grades:

• Astrocytoma Grade I, also known as Pilocystic Astrocytoma, is a low-grade tumor with slow growth.
• Astrocytoma Grade II, also known Low-Grade Astrocytoma, is a tumor also characterized by slow growth.
• Astrocytoma Grade III, also known as Anaplastic Astrocytoma, has a faster and more aggressive growth compared to Astrocytoma Grade III.
• Astrocytoma Grade IV, also known as Glioblastoma Multiforme, is the most aggressive and deadliest primary brain tumor [5].

In the United States and Europe, about 2 to 3 per 100,000 people are diagnosed with astrocytoma every year [5].

4. What Is Medulloblastoma?

Medulloblastoma is a brain tumor that arises from cells in the cerebellum whose functions have been altered by chromosomal abnormalities. However, the type of affected cells is not well-known and may involve cerebellar stem cells.

This type of brain tumor mostly affects children but can also affect adults but at a much lower frequency.

In the United States, about 1000 people are diagnosed with medulloblastoma each year [6].

5. What Is Craniopharyngioma?

Craniopharyngioma is a rare brain tumor that arises from epithelial cells located between the hypothalamus and the pituitary gland; however, the causes of this tumor formation are not known.

Craniopharyngioma is a very slow-growing tumor that affects children and adults over the age of 50. Craniopharyngioma has an incidence of about 0.13 to 2 per 100,000 people each year [7].

6. What Is Oligodendroglioma?

Oligodendroglioma is a tumor that originates from a type of glial cells known as oligodendrocytes. Although the causes are unknown, it mainly develops in the frontal and temporal lobes of the brain.

Oligodendrocytes are cells that provide support and insulation to the neurons’ axons through the production of myelin that covers the axons.

Oligodendrogliomas are categorized as Grade II (very slow-growing) and Grade III or anaplastic oligodendroglioma (very fast growing) [8].

In the United States, about 1271 people are diagnosed with oligodendroglioma each year with 11757 people living with this type of tumor [9].

7. What Are Gliomas?

Gliomas are brain tumors that arise from glial cells, including astrocytes, oligodendrocytes, and ependymal cells, leading to astrocytoma, oligodendroglioma, and ependymoma, respectively.

8. What Is Brainstem Glioma?

Brainstem Glioma is a tumor that is originated from glial cells (Astrocytes) in the brainstem which connects the cerebellum with the spinal cord and controls body functions such as heart rate, breathing, and swallowing [10].

Brainstem gliomas mostly affect children and young adults under the age of 20 years but can also affect adults [11]. Unfortunately, the causes of brainstem glioma are unknown.

Because brainstem gliomas are typically considered astrocytomas, they are categorized as astrocytomas grades I-IV [10].

9. What Is Pituitary Adenoma?

A pituitary adenoma is a tumor that develops from tissues in the pituitary gland which controls most of the functions of the endocrine system including growth, reproduction, metabolism, stress, and pain.

The pituitary gland controls these functions through the secretion of many hormones, including ACTH, GH, prolactin, FSH, LH, TSH, MSH, beta-endorphins, Vasopressin, and oxytocin.

Pituitary adenomas are categorized as benign adenomas, invasive adenomas, or carcinomas (epithelial tumors) but are also based on their ability to secrete hormones.

They affect about 1 in 5 people during their lifetime and are usually slow-growing, harmless, and less invasive [11].

10. What Is Schwannoma?

Schwannoma is a tumor that develops from Schwann cells that produce the myelin sheath which covers and insulate nerve cells in the peripherical nervous system.

Although the causes of Schwannoma are unknown, Schwannoma tumor cells are characterized by an abnormal growth compared to that of normal Schwann cells.

Depending on the affected peripheral nerves, schwannoma can affect different parts of the body (e.g., face, vestibule, or spinal cord root) through its compression effect on nerves.

Schwannoma is a rare tumor that affects around 200,000 people [12].

11. What Is Germ Cell Tumor?

Germ cell tumors are growths that originate from germ cells such as the gonads (ovaries or testes). They are categorized into benign germ cell tumors (e.g., mature teratoma) and malignant germ cell tumors (e.g., seminoma and dysgerminoma) [13].

In the United States, about 900 children and adolescents are diagnosed with germline tumors each year [14].

12. What Is Primitive Neuroectodermal Tumor?

A primitive neuroectodermal tumor (PNET) is a tumor that develops from the neuroectoderm during embryonic development affecting the brain and the spinal cord.

The neuroectoderm is an embryonic structure that later generates the hindbrain, the midbrain, and the forebrain.

Primitive neuroectodermal tumors (PNET) are fast-growing tumors (Grade IV) that mainly affect children and adults.

In the United States, about 129 people are diagnosed with PNET each year with 950 people living with this type of tumor [15].

13. What Is Primary Central Nervous System Lymphoma?

Primary central nervous system lymphoma (PCNSL) is a tumor that arises from the lymph node tissues in the brain and spinal cord.

Although the causes are unknown, PCNLCs are mostly large B-cell non-Hodgkin lymphomas and mainly affect patients with AIDS (Immunocompromised).

In the United States, about 1500 people are diagnosed with PCNL each year [16].

14. What Is Mixed Glioma?

Mixed gliomas are tumors that arise from more than one type of glial cells, including astrocytes, oligodendrocytes, and ependymal cells.

They are mostly originated from both astrocytes and oligodendrocytes resulting in oligoastrocytomas.

Mixed gliomas are categorized as Grade I and II (Slow-growing) or Grade III and IV (Fast-growing and likely invasive) [17].

15. What Is Optic Nerve Glioma?

Optic nerve glioma is a rare low-grade tumor that develops around the optic nerve causing vision problems [18]. It is mostly detected in children at the age of 5 years.

16. What Is Chordoma?

Chordoma is a slow-growing tumor originating from left-over cells, known as notochord cells, which role is associated with the formation of the spine during embryonic development.

Chordomas are mostly diagnosed in individuals in their 50s or 60s and in the sacral region (tailbone) or the region between the skull and the spine [19].

In the United States, about 300 people are diagnosed with chordoma each year, while 700 people are diagnosed with this type of tumor each year in Europe [20].

17. What Are Diffuse Astrocytomas?

Diffuse astrocytomas are grade II (slow-growing) tumors that develop from astrocytes in the cerebral hemispheres but are dispersed within the brain tissue instead of being well-defined within an area of the brain.

In the United States, about 1410 people were diagnosed with diffuse astrocytomas in 2017 [21].

18. What Is Hemangioblastoma?

Hemangioblastoma is a very rare benign vascular tumor that arises from cells lining the blood vessels in the cerebellum, brainstem, and spinal cord. The causes of hemangioblastoma are unknown.

In the United States, the incidence of hemangioblastoma was estimated at 0.014 per 100,000 people [22].

Conclusion

Brain tumors are classified based on the area or region of the brain tissue origin and how fast they grow. Depending on the affected tissues, brain tumors can affect brain function through compression or excess production of hormones.