Most cancers are "staged" so doctors can determine prognosis and treatment recommendations. Unlike other cancers, brain cancer is not "staged," because brain tumors do not spread to other areas of the body. Instead, the prognosis of and treatment recommendations for brain cancer is based on the tumor's "grade."

The tumor's grade refers to how abnormal the cancer cells look under a microscope and how quickly the tumor is likely to grow and spread. The pathologist determines the grade of the tumor using tissue removed for biopsy. The following grading system may be used for adult brain tumors:

• 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.