Types of Glioma & Astrocytoma

Three types of glial cells can produce glioma tumors. Astrocyte cells, which regulate electrical impulses in the brain, can form astrocytomas. Astrocytoma is the most common form of glioma.

Oligodendrocyte cells, which insulate nerve cells to help send nerve signals, produce oligodendrogliomas. Ependymal cells, which line the cavities of the brain, called ventricles, form ependymomas.

There are four different “grades” of gliomas, which are categorized as low-grade or high-grade. Recently, doctors have discovered that each grade of glioma is characterized by specific DNA mutations in the tumor. Doctors at NYU Langone’s Perlmutter Cancer Center can identify these mutations and provide an accurate, precision molecular diagnosis of your glioma and determine the best treatment plan for you based on the tumor’s molecular makeup.

Low-grade gliomas are grade I and grade II tumors. Grade I gliomas are rare tumors found most frequently in children. Unlike other gliomas, they may be cured with surgery. This means that if the tumor can be successfully removed by an experienced neurosurgeon, it probably won’t return. An example of a Grade I glioma is a juvenile pilocytic astrocytoma. Most grade I gliomas have DNA mutations in a gene called BRAF.

Astrocytomas and oligodendrogliomas are the most common grade II gliomas. They occur most frequently in children and young adults. Most grade II gliomas are infiltrative, which means that the tumor cells do not remain concentrated in one area, and generally cannot be cured with surgery. These tumors grow slowly over years, but eventually most transform into high-grade gliomas that can be life-threatening.

Most grade II gliomas have DNA mutations in the IDH1 or IDH2 gene. Gliomas with an IDH mutation grow more slowly than gliomas without one. Some grade II gliomas with an IDH mutation have an additional DNA irregularity called 1p/19q codeletion.  These gliomas can respond well to chemotherapy.

High-grade gliomas are grade III or grade IV tumors. Grade III gliomas include anaplastic astrocytomas and anaplastic oligodendrogliomas. Grade IV gliomas are called glioblastomas. High-grade gliomas grow rapidly and can easily spread throughout the brain. These are the most aggressive types of glioma and are life-threatening.

The majority of gliomas in adults are high-grade.

Recently, doctors have discovered that most grade III gliomas have DNA mutations in one of the IDH genes. These gliomas grow more slowly than high-grade gliomas that do not have an IDH mutation. Still, these gliomas can eventually become aggressive over time. Like low-grade gliomas with an IDH mutation, some high-grade gliomas with this mutation have an additional DNA irregularity called 1p/19q codeletion. These gliomas can respond well to chemotherapy.

Glioblastomas, which are grade IV, usually do not have an IDH mutation and are the most life-threatening gliomas. Recently, doctors have discovered that about half of glioblastomas have a DNA irregularity called MGMT methylation. These glioblastomas tend to respond better to chemotherapy than those without MGMT methylation.