What is brain tumor?
Brain tumor is a mass of abnormal cells in the brain, that develops due to uncontrolled growth of cells. It may originate in the brain cells only, known as primary brain tumor, or form due to metastasis of cancer cells from another part of body (where the cancer originally started), known as secondary brain tumor. The primary tumor can be benign or malignant (cancerous), and located in any part of the brain.
Although, the definitive causes of brain cancer is yet unknown, several genetic and environmental factors are attributed to it.
Types of brain tumor:
There are many types of primary brain tumors that can be classified based on the type of cells they originate from, location of tumor and other factors. They are mainly calssified as glioma, and non-glioma tumor types in adults.
Glioma begin in the glial or supportive tissue of the brain and are the most common type of primary brain tumor. Some common types of gliomas are:
Astrocytomas: The tumors begins in astrocytes, small, star-shaped cells and can grow in any part of the brain or spinal cord. In adults, astrocytomas most commonly arise in the cerebrum, whereas in children, they often occur in the brain stem, the cerebrum and the cerebellum.
Brain stem gliomas: This type of glioma occurs in the lowest part of the brain, near the stem. The brain stem is responsible for many vital functions of the body. Most brain stem gliomas come under high-grade astrocytomas.
Ependymomas: These tumors often develop in the lining of the ventricles in the brain or in the spinal cord. They are mostly found in childhood and adolescence, but can develop at any age.
Oligodendroglioma: This kind of tumor begins in the cells that produce myelin, the protective covering of the nerves. It usually occurs in the cerebrum and are rare. They grow slowly and normally do not spread to surrounding healthy brain tissue. They are mostly found in middle-aged adults but can occur in people of all ages.
Other types of brain tumors that do not begin in glial tissue are called Non-gliomas. Some of the most common types are:
Medulloblastomas: This kind of brain tumor develop from primitive or developing nerve cells which generally are not found in the body after birth. Medulloblastomas are therefore also referred to as primitive neuroectodermal tumors (PNET). Mostly, they begin in the cerebellum, but may occur in other parts as well. These tumors are most often found in children, more commonly in boys than girls.
Meningioma: These tumors grow from the meninges, or membranes that enclose the brain and spinal cord. They are usually benign. Because these tumors grow very slowly, the brain may be able to adjust to their presence. Meningiomas often grow quite large before they cause symptoms. They occur most often in women between 30 and 50 years of age.
Pineal region tumor: These non-gliomas are typically found in or around the pineal gland, a small organ located near the center of the brain. This tumor can be slow growing (called pineocytoma), or fast growing (called pineoblastoma). As pineal region is in the centre of the brain, it is very difficult to reach, and tumors in the part often cannot be removed surgically.
Craniopharyngioma: This type of tumor occurs in the pituitary gland, located near the hypothalamus. These are usually benign tumors but can be sometimes considered malignant as they may press upon or damage the hypothalamus, which affect certain vital functions of the brain part. They are most often found in children and adolescents.
Schwannoma: It is a rare tumor that develops in the Schwann cells, which produce the myelin that protects the nerve of hearing (acoustic nerve). These tumors are usually benign and mostly occur in adults, twice in women than men. It affects the vestibular nerve in the inner ear, which helps control balance.
Germ cell tumors: These types of tumors occur in the developing sex cells or germ cells. Germinoma is the most common type of germ cell tumor in the brain.