Glioma is the most common malignant tumor in the skull, accounting for approximately 40% of intracranial tumors. The World Health Organization classifies the pathological types of gliomas into four grades, of which grade I is benign glioma, grade II is a low-grade malignant glioma, and grades III-IV are highly malignant gliomas. Unfortunately, grade I gliomas are rare, whereas grade IV gliomas account for 50% of gliomas. All gliomas of grades II-IV recur. Many patients and friends have difficulty understanding the problem of recurrence of glioma, thinking that the doctor opened the tumor off and the doctor said it was clean, how can it still recur? In fact, the degree of complete glioma removal is relative. Generally speaking, if the surgeon removes the tumor visible to the naked eye, it is considered clean. However, due to the infiltrative growth of glioma, some tumor cells are mixed with normal brain tissues and look like normal tissues, which can deceive the doctor’s eyes. Therefore, doctors sometimes expand the scope of resection and remove part of the seemingly normal peri-tumor tissue, but even so, it fails to prevent the recurrence of malignant glioma because the degree of infiltration of malignant glioma cells is beyond the imagination of the general public. Since brain tissue is functional and does not allow for arbitrary resection, the scope of extended resection is ultimately limited. Moreover, even if one hemisphere with a tumor is completely removed, the opposite hemisphere may still have glioma growth. Hu Dezhi, Department of Neurosurgery, Huashan Hospital, Fudan University