Types of Brain Tumors

There are many different types of brain tumors. They are usually categorized by the type of cell where the tumor begins, or they are also categorized by the area of the brain where they occur. The most common types of brain tumors include the following:

Gliomas
The most common type of primary brain tumor is a glioma. Gliomas begin from glial cells, which are the supportive tissue of the brain. There are several types of gliomas, categorized by where they are found, and the type of cells that originated the tumor. The following are the different types of gliomas:

• Astrocytomas
  Astrocytomas are glial cell tumors that are derived from connective tissue cells called astrocytes. These cells can be found anywhere in the brain or spinal cord. Astrocytomas are the most common type of childhood brain tumor, and the most common type of primary brain tumor in adults. Astrocytomas are generally subdivided into high-grade or low-grade tumors. High-grade astrocytomas are the most malignant of all brain tumors. Astrocytomas are further classified for presenting signs, symptoms, treatment, and prognosis, based on the location of the tumor. The most common location of these tumors in children is in the cerebellum, where they are called cerebellar astrocytomas. These persons usually have symptoms of increased intracranial pressure, headache, and vomiting. There can also be problems with walking and coordination, as well as double vision. In adults, astrocytomas are more common in the cerebral hemispheres (cerebrum), where they commonly cause increased intracranial pressure (ICP), seizures, or changes in behavior.


• Brain stem gliomas
  Brain stem gliomas are tumors found in the brain stem. Most brain stem tumors cannot be surgically removed because of the remote location and delicate and complex function this area controls. Brain stem gliomas occur almost exclusively in children; the group most often affected is the school-age child. The child usually does not have increased intracranial pressure (ICP), but may have problems with double vision, movement of the face or one side of the body, or difficulty with walking and coordination.


• Ependymomas
  Ependymomas are also glial cell tumors. They usually develop in the lining of the ventricles or in the spinal cord. The most common place they are found in children is near the cerebellum. The tumor often blocks the flow of the CSF (cerebral spinal fluid, which bathes the brain and spinal cord), causing increased intracranial pressure. This type of tumor mostly occurs in children younger than 10 years of age. Ependymomas can be slow growing, compared to other brain tumors, but may recur after treatment is completed. Recurrence of ependymomas results in a more invasive tumor with more resistance to treatment.


• Optic nerve gliomas
  Optic nerve gliomas are found in or around the nerves that send messages from the eyes to the brain. They are frequently found in persons who have neurofibromatosis, a condition a child is born with that makes him/her more likely to develop tumors in the brain. Persons usually experience loss of vision, as well as hormone problems, since these tumors are usually located at the base of the brain where hormonal control is located. These are typically difficult to treat due to the surrounding sensitive brain structures.


• Oligodendrogliomas
  This type of tumor also arises from the supporting cells of the brain. They are found commonly in the cerebral hemispheres (cerebrum). Seizures are a very common symptom of these tumors, as well as headache, weakness, or changes in behavior or sleepiness. This tumor is more common in persons in their 40s and 50s. These tumors have a better prognosis than most other gliomas, but they can become more malignant with time.

Metastatic tumors
In adults, metastatic brain tumors are the most common type of brain tumors. These are tumors that begin to grow in another part of the body, then spread to the brain through the bloodstream. When the tumors spread to the brain, they commonly go to the part of the brain called the cerebral hemispheres, or to the cerebellum. Often, a patient may have multiple metastatic tumors in several different areas of the brain. Lung, breast, and colon cancers frequently travel to the brain, as do certain skin cancers. Metastatic brain tumors may be quite aggressive and may return even after surgery, radiation therapy, and chemotherapy.

Meningiomas
Meningiomas are usually benign tumors that come from the meninges or dura, which is the tough outer covering of the brain just under the skull. This type of tumor accounts for about 15 percent of brain tumors. They are slow growing and may exist for years before being detected. Meningiomas are most common in patients in their 40s and 50s. They are commonly found in the cerebral hemispheres just under the skull. They usually are separate from the brain and can sometimes be removed entirely during surgery. They can, however, recur after surgery and certain types can be malignant.

Schwannomas
Schwannomas are benign tumors, similar to meningiomas. They arise from the supporting cells of the nerves leaving the brain, and are most common on the nerves that control hearing and balance. When schwannomas involve these nerves, they are called vestibular schwannomas or acoustic neuromas. Commonly, they present with loss of hearing, and occasionally loss of balance, or problems with weakness on one side of the face. Surgery can be difficult because of the area of the brain in which they occur, and the vital structures around the tumor. Occasionally, radiation (or a combination of surgery and radiation) is used to treat these tumors.

Pituitary tumors
The pituitary gland is a gland located at the base of the brain. It produces hormones that control many other glands in the body. These glands include the thyroid gland, the adrenal glands, the ovaries and testes, as well as milk production by pregnant women, and fluid balance by the kidney. Tumors that occur in or around the area of the pituitary gland can affect the functioning of the gland, or overproduce hormones that are sent to the other glands. This can lead to problems with thyroid functioning, impotence, milk production from the breasts, irregular menstrual periods, or problems regulating the fluid balance in the body. In addition, due to the closeness of the pituitary to the nerves to the eyes, patients may have decreased vision. Tumors in the pituitary are frequently benign, and total removal makes the tumors less likely to recur. Since the pituitary is at the base of the skull, approaches for removal of a pituitary tumor may involve entry through the nose or the upper gum. Certain types of tumors may be treated with medication, which, in some cases, can shrink the tumor or stop the growth of the tumor.

Primitive neuroectodermal tumors (PNET)
PNET can occur anywhere in the brain, although the most common place is in the back of the brain near the cerebellum. When they occur here, they are called medulloblastomas. The symptoms depend on their location in the brain, but typically the patient experiences increased intracranial pressure. These tumors are fast growing and often malignant, with occasional spreading throughout the brain or spinal cord.

Medulloblastomas
Medulloblastomas are one type of PNET that are found near the midline of the cerebellum. This tumor is rapidly growing and often blocks drainage of the CSF (cerebral spinal fluid, which bathes the brain and spinal cord), causing symptoms associated with increased ICP. Medulloblastoma cells can spread (metastasize) to other areas of the central nervous system, especially around the spinal cord. A combination of surgery, radiation, and chemotherapy is usually necessary to control these tumors.

Craniopharyngioma
Craniopharyngioma are benign tumors that occur at the base of the brain near the nerves from the eyes to the brain, and the hormone centers. Most persons with this type of brain tumor develop symptoms before the age of 20. Symptoms include headaches, as well as problems with vision. Hormonal imbalances are common, including poor growth and short stature. Symptoms of increased intracranial pressure may also be seen. Although these tumors are benign, they are hard to remove due to the sensitive brain structures that surround them.

Pineal region tumors
Many different tumors can arise near the pineal gland, a gland that helps control sleep and wake cycles. Gliomas are common in this region, as are pineal blastomas. In addition, germ cell tumors, another form of malignant tumor, can be found in this area. Tumors in this region are more common in children than adults, and make up 3 to 8 percent of pediatric brain tumors. Benign pineal gland cysts are also seen in this location, which makes the diagnosis difficult between what is malignant and what is benign. Biopsy or removal of the tumor is frequently necessary to tell the different types of tumors apart. Persons with tumors in this region frequently experience headaches or symptoms of increased intracranial pressure. Treatment depends on the tumor type and size.