What are the most common types of brain tumors?

The most common types of brain tumors in adults are gliomas and astrocytic tumors, according to WebMD. In children, brain tumors are most commonly astrocytomas, states the National Cancer Institute.

Gliomas are tumors that form in the brain’s supportive tissue known as glial tissue, according to WebMD. Astrocytomas are a type of glioma that form in astrocytes, one of several types of glial cells that make up the glial tissue.

The World Health Organization defines four classifications of astrocytomas based on growth rate and how likely they are to spread to nearby tissue, according to WebMD. Grade I astrocytomas are slow growing and unlikely to spread, while Grade IV astrocytomas are the most aggressive.