My wife went through this about a year ago. They do this because brain cancers are so invasive that you basically want to remove as much brain matter around the

My wife went through this about a year ago. They do this because brain cancers are so invasive that you basically want to remove as much brain matter around the tumor as possible with minimal functional deficiency afterwards. This is a tradeoff because it means they would want to take more, but cannot due to the functional impairment. They stimulate the brain with electric probes to find the coherent structures within the brain. This technique is actually quite old, pioneered in Canada over 50 years ago, and proliferated recently at UCSF. It is a miracle to those with benign cancers, but in most cases prolongs life by months not years unfortunately.