Tumors are graded in accordance with how normal or abnormal the cells appear. Doctors plan treatment based on this observation. Staging also gives them an idea about how fast brain tumor is likely to spread.
Grade 1 brain tumors are low grade malignant and slow-growing. It is easy to confuse them with identical healthy cells.
Grade 2 brain tumors are malignant and slow-grading. They have high chance of recurrence and are likely to spread to surrounding tissues.
Grade 3 brain tumors appear abnormal and actively metastasize into surrounding regions of the brain and are very likely to recur.
Grade 4 brain tumors look highly malignant and actively metastasize into surrounding tissues of the brain. Rarely some benign tumors can become malignant and a lower grade tumor may recur with a higher grade.
Read more on the treatment for brain tumor