WHO – Grades
The World Health Organization (WHO) divides brain tumors into 4 groups based on their growth behavior. Grade 1 tumors grow slowly and are considered benign. Grade 4 tumors grow extremely fast and have a very poor prognosis.
Grade 2 and 3 tumors are in between. A glioblastoma is a tumor that originates from the supporting or envelope cells of the nerve cells, which are called glial cells in medical terminology. This is where the name comes from.
Due to its rapid growth and poor prognosis, glioblastomas are grade 4 tumors. While grade 1 tumors are called benign brain tumors by the WHO, grade 2 tumors are already occasionally malignant cells detectable. In 50% of grade 2 tumors, a new tumor with a higher malignancy grade (grades 3-4) develops in the course of the disease, thus limiting life expectancy.
Similar to gliobastoma, these tumors originate from the supporting or envelope cells of the brain. In contrast to glioblastoma, a grade 4 tumor, grade 2 brain tumors grow much more slowly and have a much better prognosis. Grade 3 tumors are malignant brain tumors with rapid growth according to the classification of the World Health Organization (WHO).
The prognosis is poor. Despite therapy, many patients die after 2-3 years. Typical grade 3 tumors are so-called anaplastic astrocytomas; like the glioblastomas against them from the supporting and envelope cells of the nerve cells.
However, glioblastomas are group 4 tumors because of their even more rapid growth. Despite maximum therapy, the mean survival time is about 1 year. Grade 4 tumors are even more malignant, grow faster and lead to a significant reduction in life expectancy despite therapy.
The classification of the tumor into the corresponding WHO grade therefore strongly influences the prognosis of the patient. Glioblastomas are always grade 4 tumors with a very poor prognosis. Of course, other factors such as operability, localization and response to chemo- and/or radiotherapy also play an important role in the patient’s prognosis. The median survival time for a glioblastoma is on average one year after diagnosis.
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