Total resection means that the tumor must have a border. If the tumor has a border, we can remove it along the border, and total resection is not difficult. The problem is that diffuse low-grade gliomas do not have borders, so there is no concept of total resection. The reason why there is no boundary is that there is no good means to determine the boundary. Currently, MRI is the most common means of diagnosing glioma. And MRI can only show up when the tumor cell density is greater than 500 cells/mm3, meaning, MRI does not show up when the tumor cell density is less than 500 cells/mm3. That is, there are tumor cells in the area where MRI is normal, and the exact extent and distance of the three-dimensional spatial distribution are not known. From this perspective, total excision is a pseudo-proposition. Of course, the absence of boundaries does not mean that one has to compromise, not to do nothing. For example, at least the areas where MRI shows abnormalities should be removed as much as possible (except for overlap with functional areas). If the tumor is in a non-functional area, remove it as large as possible, cutting to the anatomical border as appropriate. If you cannot get 100 points, try to get a high score. 90 points is better than 80 points. If the battle with the enemy is not destined to be won, at least lose a little decently and stalemate a little longer. Therefore, with the concept of functional brain boundary, we can cut all the way to the functional boundary before stopping the surgery. This is the maximum safe resection.