Brain tumor staging

Staging is a way of describing a tumor, such as where it is located, if or where it has spread, and whether it is affecting the functions of other organs in the body. A staging system is used for most other types of cancer. There is a formal staging system for adult brain tumors; however, the grading system described below is always used instead.

After a brain tumor has been diagnosed, additional tests will be done to learn more about the tumor. If the tumor is a glial brain tumor, the pathologist will assign a “grade” using a number from I to IV (one to four). The grade indicates how different the tumor cells are from healthy cells, with a higher grade tumor having cells that are the least like healthy cells. The characteristics of the tumor, as seen under the microscope, help determine how cancerous a tumor is. Generally, the lower the grade, the better the prognosis (chance of recovery or long-term control of the tumor).

WHO histologic grading for CNS tumors:

Grade I:

• Lesions with low proliferative potential, a frequently discrete nature, and the possibility of cure following surgical resection alone
• Juvenile pilocytic astrocytoma, subependymal giant cell astrocytoma

Grade II:

• Lesions that are generally infiltrating and low in mitotic activity but recur; some tumor types tend to progress to higher grades of malignancy
• Diffuse astrocytoma, oligodendroglioma, oligoastrocytoma

Grade III:

• Lesions with histologic evidence of malignancy, generally in the form of mitotic activity, clearly expressed infiltrative capabilities, and anaplasia
• Anaplastic astrocytoma, anaplastic oligoastrocytoma, anaplastic oligoastrocytoma

Grade IV:

• Lesions that are mitotically active, necrosis-prone, and generally associated with a rapid preoperative and postoperative evolution of disease
• Glioblastoma