**2. Different surgical options**

Gliomas represent 30% of all brain tumors and 80% of all malignant brain tumors [1]*.* The origin of gliomas are the transformed glioma cells of the central nervous system. Gliomas can be classified by cell type, localization, and grade. The grade classification is performed by World Health Organization (WHO) in 2016 and widely used [2].

There are four grades of gliomas:

Grade I—pilocytic astrocytoma;

Grade II—diffuse astrocytoma, oligodendroglioma;

Grade III—malignant glioma: anaplastic astrocytoma, anaplastic oligodendroglioma;

Grade IV—glioblastoma multiforme (IDH wild type and mutant), diffuse midline glioma, H3 K27M-mutant.

Grade I and II gliomas are classified as low grade glioma (LGG) and grade III and IV as high grade glioma (HGG). Surgical treatment options are different for every group of gliomas, LGG and HGG, due the glioma life cycle [2].
