A biopsy can then be performed to identify the type of brain tumor and whether it is malignant (cancerous). During a biopsy, a small amount of the cancerous tissue is taken and analyzed under a microscope. A biopsy can usually be done during surgery in which all or part of the brain tumor is removed. Tumors buried deep in the brain sometimes cannot be approached safely. In those cases, a biopsy procedure involves using three-dimensional needle technique in which special imaging equipment guides the placement of a needle to allow cells to be drawn into the needle.