Before your doctor can recommend a treatment plan, he or she needs to know the grade of the cancer. The grade tells these things about the tumor:
How malignant it is
How likely it is that the cancer will spread to other parts of the brain
How it might respond to treatment
How likely it is to come back (recurrence) after treatment
A pathologist, a doctor who specializes in looking at tissue under a microscope, determines the grade by looking at the sample of tissue you had removed in a biopsy.
There are 4 grades of brain tumors. Grade I and II are also called low-grade tumors. Grade III and IV are also called high-grade or anaplastic tumors:
Grade I. Grade I tumors are the least malignant. Cells in a grade I tumor look like normal brain cells. Your doctor may remove grade I tumors 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. Grade II tumors have cells that are not normal when looked at under a microscope. They can grow and invade the tissues around them. Even if they are entirely removed with surgery, these tumors can come back at a higher grade. Low-grade (diffuse) astrocytomas are examples of grade II tumors.
Grade III. Grade III tumors are also malignant tumors. These tumors invade the tissues around them. When grade III tumors are removed with surgery, they usually grow back faster than grade II tumors. Grade III tumors frequently turn into grade IV tumors. An example of a grade III tumor is anaplastic astrocytoma.
Grade IV. Grade IV tumors are the most malignant tumors. Grade IV tumor cells are very abnormal. They grow and spread quickly and infiltrate areas of the brain that appear normal. Grade IV tumors produce new blood vessels to help the tumor grow. Surgery cannot reach these areas without damaging the normal brain. For this reason, chemotherapy and radiation are routinely given for a grade IV brain tumor. An example of a grade IV tumor is glioblastoma multiforme.
Researchers continue to look for clues that will make brain tumors easier to diagnose and stage. New findings may help doctors figure how quickly a tumor will grow and make more accurate predictions about a patient's prognosis.