High-grade gliomas are more malignant and less effective in treatment compared to low-grade gliomas. Under the current treatment paradigm, even if the tumor is first removed through microsurgery and then treated with a combination of radiotherapy and tumor electric field therapy, eventual recurrence of high-grade glioma is almost inevitable. However, there are many types of high-grade glioma, so the time of recurrence after treatment varies, and a small percentage of high-grade glioma can survive for more than 5 years or even 10 years. Moreover, the recurrence of high-grade glioma does not mean that there is no treatment at all. Some of the recurrence of high-grade glioma can be remitted for a certain period of time through reoperation and adjuvant radiotherapy, targeted therapy and immunotherapy. Will high-grade gliomas become less malignant, lower-grade gliomas after recurrence? In general, gliomas will progress from a low grade glioma of low malignancy to a high grade glioma of high malignancy, but not vice versa from a high grade glioma of high malignancy to a low grade glioma of low malignancy. However, in actual clinical cases, there are cases that started as high-grade gliomas, but after recurrence, the pathological diagnosis is indeed a low-grade glioma. This is because the pathological examination does not take the components of high-grade glioma, which is partly because high-grade glioma is also a mixture of high- and low-grade glioma cells, and the pathological examination may take the components of low-grade. In addition, after surgical resection and radiotherapy, what remains of high-grade glioma is actually necrotic or partially necrotic tumor cells, which may also be taken as part of the tissue during pathology. High-grade glioma will not convert to low-grade glioma. For cases where high-grade glioma is diagnosed in the first surgery but low-grade glioma is diagnosed after recurrence, the pathological results of the two surgeries need to be checked and combined with the characteristics of glioma biological behavior conversion in order to make a correct judgment and formulate a reasonable follow-up treatment plan.