Tumor grade

What it is

Tumor grade is a measure of how aggressive a tumor is expected to be — essentially, how quickly it is likely to grow and spread. For gliomas, the grade is determined by how the tumor looks under the microscope and, increasingly, by its molecular features. It is one of the most important factors in predicting behavior and guiding treatment.

Understanding Tumor grade

Grading reflects features such as how abnormal the cells appear, how rapidly they are dividing, and whether aggressive features (like abnormal blood vessel growth or dead tumor tissue, called necrosis) are present. Lower-grade gliomas tend to grow more slowly, while higher-grade gliomas grow and spread more aggressively. In the modern (WHO CNS5) system, certain molecular markers can influence or determine the grade, not just the microscopic appearance. Grade is distinct from "type" (the kind of glioma): a complete diagnosis includes both, such as "astrocytoma, IDH-mutant, grade 2." Grade strongly influences treatment intensity and prognosis. Understanding tumor grade clarifies one of the central pieces of information in a glioma diagnosis. Understanding grade clarifies how aggressiveness is measured and why it guides care.

Why it matters

Understanding tumor grade helps patients and families interpret one of the most important parts of a glioma diagnosis — how aggressive the tumor is expected to be — which strongly shapes treatment and outlook.