Grade I
The tumor grows slowly, has cells that look similar to normal cells, and rarely spreads into nearby tissues. It may be possible to remove the entire tumor by surgery.
Grade II
The tumor grows slowly, but may spread into nearby tissue and may become a higher-grade tumor.
Grade III
The tumor grows quickly, is likely to spread into nearby tissue, and the tumor cells look very different from normal cells.
Grade IV
The tumor grows very aggressively, has cells that look very different from normal cells, and is difficult to treat successfully.
The chance of recovery (prognosis) and choice of treatment depend on the type, grade, and location of the tumor and whether cancer cells remain after surgery and/or have spread to other parts of the brain.
Types of Adult Brain Tumors
The extent or spread of cancer is usually described as stages. There is no standard staging system for brain tumors. Primary brain tumors may spread within the central nervous system (brain and spinal cord), but they rarely spread to other parts of the body. For treatment, brain tumors are classified by the type of cell in which the tumor began, the location of the tumor in the central nervous system, and the grade of the tumor.
Types of adult brain tumors include the following:
Brain Stem Gliomas
These are tumors that form in the brain stem, the part of the brain connected to the spinal cord. They are often high-grade. Brain stem gliomas that are high-grade or spread widely throughout the brain stem are difficult to treat successfully. To prevent damage to healthy brain tissue, brain stem glioma is usually diagnosed without a biopsy.
Pineal Astrocytic Tumor
Pineal tumors form in or near the pineal gland. The pineal gland is a tiny organ in the brain that produces the hormone melatonin, a substance that helps control our sleeping and waking cycle. There are several kinds of pineal tumors. Pineal astrocytic tumors are astrocytomas that occur in the pineal region and may be any grade.
Pilocytic Astrocytoma (grade I)
Astrocytomas are tumors that start in brain cells called astrocytes. Pilocytic astrocytomas grow slowly and rarely spread into the tissues around them. These tumors occur most often in children and young adults. They usually can be treated successfully.
Diffuse Astrocytoma (grade II)
Diffuse astrocytomas grow slowly, but they often spread into nearby tissues. Some of them progress to a higher grade. They occur most often in young adults.
Anaplastic Astrocytoma (grade III)
Anaplastic astrocytomas are also called malignant astrocytomas. They grow rapidly and spread into nearby tissues. The tumor cells look different from normal cells. The average age of patients developing anaplastic astrocytomas is 41 years.
Glioblastoma (grade IV)
Glioblastomas, also referred to as glioblastomas multiforme, are malignant astrocytomas that grow and spread aggressively. The cells look very different from normal cells. Glioblastoma is also called glioblastoma multiforme or grade IV astrocytoma. They occur most often in adults between the ages of 45 and 70 years.
Oligodendroglial Tumors
Oligodendroglial tumors begin in the brain cells called oligodendrocytes, which support and nourish nerve cells. Grades of oligodendroglial tumors include the following:
- Oligodendroglioma (grade II): Oligodendrogliomas are slow-growing tumors with cells that look very much like normal cells. These tumors occur most often in patients between the ages of 40 and 60 years.
- Anaplastic oligodendroglioma (grade III): Anaplastic oligodendrogliomas grow quickly and the cells look very different from normal cells.
Mixed Gliomas
Mixed gliomas are brain tumors that contain more than one type of cell. The prognosis is affected by the cell type with the highest grade present in the tumor.
- Oligoastrocytoma (grade II): Oligoastrocytomas are slow-growing tumors composed of cells that look like astrocytes and oligodendrocytes.
- Anaplastic oligoastrocytoma (grade III): These are higher-grade oligoastrocytomas. The average age of patients developing anaplastic oligoastrocytomas is 45 years.
Ependymal Tumors
Ependymal tumors usually begin in cells that line the spaces in the brain and around the spinal cord. These spaces contain cerebrospinal fluid, a liquid that cushions and protects the brain and spinal cord. Grades of ependymal tumors include the following:
- Grade I and grade II ependymomas: These ependymomas grow slowly and have cells that look very much like normal cells. They can often be removed completely by surgery.
- Anaplastic ependymoma (grade III): Anaplastic ependymomas grow very quickly.
Medulloblastoma (grade IV)
Medulloblastomas are brain tumors that begin in the lower back of the brain. They are formed from abnormal brain cells at a very early stage in development. Medulloblastomas are usually found in children or young adults between the ages of 21 and 40 years. This type of cancer may spread from the brain to the spine through the cerebrospinal fluid.
Pineal Parenchymal Tumors
Pineal parenchymal tumors form from parenchymal cells or pinocytes, the cells that make up most of the pineal gland. These differ from pineal astrocytic tumors, which are astrocytomas that form in tissue that supports the pineal gland. Grades of pineal parenchymal tumors include the following:
- Pineocytomas (grade II): Pineocytomas are slow-growing pineal tumors that occur most often in adults aged 25 to 35.
- Pineoblastomas (grade IV): Pineoblastomas are rare and highly malignant. They usually occur in children.
Meningeal Tumors
Meningeal tumors form in the meninges, thin layers of tissue that cover the brain and spinal cord. Types of meningeal tumors include the following:
- Grade I meningioma: Meningiomas are the most common meningeal tumor. Grade 1 meningiomas are slow-growing and benign. They are found most often in women.
- Grade II and III meningiomas and hemangiopericytomas: These are rare malignant meningeal tumors. They grow quickly and are likely to spread within the brain and spinal cord. Grade III meningiomas are more common in men. Hemangiopericytomas often recur after treatment and most of them spread to other parts of the body.
Germ Cell Tumor
Germ cell tumors arise from germ cells, cells that are meant to form sperm in the testicles or eggs in the ovaries. These cells may travel to other parts of the body and form tumors. Types of germ cell tumors include germinomas, embryonal cell carcinomas, choriocarcinomas, and teratomas. They can occur anywhere in the body and can be either benign or malignant. In the brain, they usually form in the center, near the pineal gland, and can spread to other parts of the brain and spinal cord. Most germ cell tumors occur in children.
Craniopharyngioma (grade II)
Craniopharyngiomas occur in the sellar region of the brain, near the pituitary gland. The pituitary gland is a small organ about the size of a pea, located at the base of the brain. This gland controls many of the body's functions, especially growth. In adults, these tumors occur most often after the age of 50 years. Craniopharyngiomas can press on vital brain tissue and cause symptoms to appear. The tumors can also block fluid in the brain and cause swelling. The prognosis is good for craniopharyngiomas that are completely removed in surgery.
- Primary pituitary tumors: These benign tumors also occur in this region arising from the underside of the brain. The pituitary gland controls most of the hormone production in the body. It is close to where the optic nerves cross under the brain and can cause visual symptoms such as partial losses of vision.
Recurrent Adult Brain Tumor
Recurrent adult brain tumor is a tumor that has recurred (come back) after it has been treated. Adult brain tumors often recur, sometimes many years after the first tumor. The tumor may come back in the brain or in other parts of the body.
Metastatic or Secondary Brain Tumors
The types of cancer that commonly spread to the brain are cancers of the lung, breast, unknown primary site, melanoma, and colon. About half of metastatic spinal cord tumors are caused by lung cancer.
Prognosis depends on the following:
- Whether the patient is younger than 60 years.
- Whether there are fewer than 3 tumors in the brain and/or spinal cord.
- The location of the tumors in the brain and/or spinal cord.
- How well the primary tumor responds to treatment.
- Whether the primary tumor continues to grow or spread.
The prognosis is better for brain metastases from breast cancer than from other types of primary cancer.
The prognosis is worse for brain metastases from colon cancer.
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