Once your healthcare provider knows you have a brain tumor, the next step is to find out the grade of the tumor. The grade refers to how the cancer cells look when compared to normal brain cells. Grade is determined when a tissue sample (biopsy) and other tests are done on the cancer.
The grade of your tumor will help your healthcare provider know:
How quickly the tumor is likely to grow
How likely it is that the tumor will spread to other parts of the brain
How it might respond to treatment
How likely it is to grow back after treatment
There are 4 grades of brain tumor. Grade I and II are also called low-grade tumors. Grade III and IV are also called high-grade or anaplastic tumors. The grades are:
Grade I. This kind of tumor is the least malignant. Cells in a grade I tumor look a lot like normal brain cells. Your doctor may remove a grade I tumor with surgery, if it can be done safely. Or your doctor may follow the progress of a grade I tumor with yearly MRI scans.
Grade II. This kind of tumor has cells that are not normal when looked at under a microscope. They can grow and invade the tissues around them. Even if they are fully removed with surgery, this kind of tumor can sometimes come back at a higher grade. Low-grade (diffuse) astrocytoma is an example of a grade II tumor.
Grade III. This kind of tumor has cells that look more abnormal under the microscope. This kind of tumor grows into the tissues around it. When a grade III tumor is removed with surgery, it usually grows back faster than a grade II tumor. A grade III tumor often turns into a grade IV tumor. An example of a grade III tumor is anaplastic astrocytoma.
Grade IV. This kind of tumor is the most malignant. Grade IV tumor cells are very abnormal. They grow and spread quickly into areas of the brain. Surgery can’t reach all of these areas without harming the brain, so other types of treatment are often needed. An example of a grade IV tumor is glioblastoma multiforme.
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