Brain Tumor Grades
Brain tumors are classified by the microscopic structure of their tissues and unique molecular characteristics. They are also graded to indicate how aggressive they are, using the CNS World Health Organization (WHO) scale from grade 1 (least aggressive) to grade 4 (most aggressive).
Knowing both the type and grade of a brain tumor helps the health care team predict how it may behave, determine the best treatment options, and identify potential eligibility for clinical trials.
Primary brain tumors are named based on the type of cells they form in, while the grade reflects how abnormal the cancer cells appear under a microscope or through genetic and protein changes. After a biopsy and lab analysis, your doctor will share the tumor’s type and grade with you to guide the next steps in care.
| Grade | Description |
|---|---|
| Grade I (Low-grade) | Cells resemble normal brain cells and grow slowly. Rarely spread to nearby tissue. May be cured with surgery alone. |
| Grade II | Cells grow more slowly than grade III or IV but may spread into nearby tissue. Can return after treatment and potentially progress to a higher grade. |
| Grade III | Cells appear more abnormal and grow more quickly. Likely to invade the surrounding brain tissue. |
| Grade IV (High-grade) | Cells look very abnormal, grow rapidly, and often contain areas of dead tissue. Usually cannot be cured and requires aggressive treatment. |
It’s important to note that low-grade tumors can evolve into high-grade tumors over time. Because tumors may show characteristics of multiple grades, doctors treat based on the highest grade observed in the biopsy.