How are Brain Tumors classified; according to grade from I-IV
Grade I tumors are often considered benign and tend to grow slowly. The brain tissue is similar to normal brain cells. Grade II tumors are malignant and the cells look less like normal brain cells than Grade I. In grade III tumors, the malignant cells look very different than normal cells, and grow rapidly, referred to as anaplastic. Grade IV tumors have the most abnormal appearance and tend to grow the most rapidly and are usually the most aggressive. Grades I-II tumors are considered low grade, while Grades III-IV are considered high grade.
There are two major categories of brain tumors, primary brain tumors, which start in the brain and rarely spread outside the nervous system, and metastatic brain tumors, which develop in other parts of the body (for example, breast, lung, skin) and spread to the brain.
Metastatic tumors are the most commonly occurring brain tumors, with an incidence rate 10 times greater than primary brain tumors. These include:
- Gliomas are the most common class of primary brain tumor and are formed from the glial cells that provide structural support for the neurons (the thinking cells in the brain). The more common gliomas include:
- Astrocytomas are the most common type of glioma and are graded I, II, III, or IV. The most common and aggressive form is grade IV astrocytoma, also known as glioblastoma multiforme, or GBM. All forms of astrocytoma can develop anywhere in the central nervous system.
- Ependymomas develop in the hollow cavities of the brain or in the spinal cord and are often benign and slow growing.
- Oligodendrogliomas originate in the cells that provide support for the connection “wires” between neurons.
There are also many types of non-glial brain tumors; however, most are rare:
- Craniopharyngiomas develop in the pituitary gland region, most often in children and adolescents.
- Meningiomas occur in the membranes protecting the brain and spinal cord and are usually slow growing and benign. Malignant meningiomas are less common, but grow more quickly.
- Pineal tumors are found near the center of the brain and are difficult to completely remove.
There are many types of brain tumors that are named based on the type of brain cells they originated from. Most primary brain tumors begin from glial cells in the brain and are called gliomas. One type of glioma is an astrocytoma, which can be any grade. Grade I-II astrocytomas are often called a low grade glioma. A grade III astrocytoma is sometimes called an anaplastic astrocytoma, while a grade IV may be called a glioblastoma.
Meningiomas are tumors that arise from the brain’s meninges and can be grade I-III, though are usually grade I and tend to grow slowly. Oligodenrogliomas come from the cells that surround and protect nerves. These can be Grade II–III.
At this time we still don’t know what causes most brain tumors. There are some rare cases of brain tumors running in families though the vast majority of brain tumors are not related to family genetics. There continues to be ongoing research into areas such as cell phone use, head injury, and chemical use to evaluate for a link, though so far there have not been any consistent results that show a cause.
The symptoms of a brain tumor can vary from person to person. They may include headache, visual changes, seizures, weakness or changes in mood or memory, to name a few.
Brain tumors are often treated differently depending on the type, location and grade of tumor. These options may include surgery, radiation therapy and chemotherapy. Surgery is usually the first treatment, and may involve removing all or part of the tumor. Depending on the grade and type of tumor, location as well as the patient’s age and overall health, this may be followed by additional treatment. This may include both radiation and chemotherapy. Radiation and chemotherapy are often given in combination following surgery for a period of several weeks. This may be followed by chemotherapy alone for a period of time. Depending on the type of chemotherapy, this may be given as either oral medication or intravenously.
While being treated, patients will typically have regular monitoring with frequent MRI’s of the brain as well as regular follow up with their doctors including surgeons, radiation and medical oncologists. We continue to learn more and more through research and clinical trials into the various types of brain tumors. This research has led to improved treatments that are helping patients to live longer and with a better quality of life than ever before.
While tumor tissue biopsy and the tumor’s appearance under the microscope is still the standard of care for diagnosing and naming brain tumors, deeper knowledge of the molecular underpinnings of a tumor’s DNA can help direct treatments and improve outcomes. To better define a tumor’s behavior and for choosing possible targets for therapy, physicians now profile most patients’ tumor’s DNA to identify the driver mutations. Even among patients with the same type of cancer, the behavior of the cancer and its response to treatment can vary widely, based on these genetic changes.
It is increasingly clear that specific characteristics of cancer cells and cancer patients can have a profound impact on prognosis and treatment outcome. Targeted therapies are based on the type of tumor and its profile. Although factoring these characteristics into treatment decisions makes cancer care more complex, it also offers the promise of improved outcomes. Targeted therapies for each tumor lead to better outcomes through personalized medicine.
Treating Brain Tumors
Treatment for brain tumors is determined by many factors, including tumor type; grade; size and location in the brain; whether it’s newly diagnosed or a recurrence; the tumor’s specific genetic makeup; and your overall health. The potential benefits of a singular or combination of treatments or participation in a clinical trial must be carefully balanced with the potential risks.
Surgery is an important treatment for most brain tumors. This is especially true if located within the membranes covering the brain or in an area where removal would not damage the surrounding areas. Even if the entire tumor cannot be removed, surgery can relieve some symptoms caused by the tumor. Many benign tumors are treated only by surgery.
Most malignant tumors also require treatment after surgery such as radiation therapy, chemotherapy, electrical field therapy, or targeted drug therapy.