Methods and systems for distinguishing an astrocytic human brain rumor from a non-astrocytic human brain tumor (FIG. 4). In one embodiment a method includes the steps of staining tumor tissue from a subject suspected of having a brain tumor with SR101 and visualizing the tissue stained with SR101 with a fluorescence imaging device to confirm an astrocytic or non-astrocytic tumor type. Advantageously, rumor tissue from a subject is stained ex vivo, and the staining and visualizing steps are performed intraoperatively so as to guide the surgeon and thereby minimize or eliminate the need for a subsequent surgery.