The most common grading system we use today for gliomas is still the one developed by the World Health Organization (WHO). It classifies gliomas into 4 grades. We usually refer to low-grade gliomas as grade I and II gliomas; high-grade gliomas are grade III and IV tumors. Grade I gliomas have the best healing process and are benign tumors, the most common being hairy cell astrocytomas. Grade II and above are malignant tumors. Grade II tumors are relatively less malignant and have a better prognosis, and the main types are diffuse astrocytoma and oligodendroglioma. Grade III gliomas are relatively more malignant and have poorer prognosis, mainly including mesenchymal astrocytoma and mesenchymal oligodendroglioma. Grade IV gliomas with the highest level of malignancy, also known as glioblastoma, have the worst prognosis, with rapid recurrence and short survival. It should be noted that the prognosis cannot be measured by the grade alone, but also by the type of tumor and genetic mutation, etc. Grade IV gliomas can survive for more than five to ten years. Grade II gliomas include diffuse astrocytomas, oligodendrogliomas and ventricular meningiomas.