The prodrug, 5-Aminolevulinic acid (ALA), has been shown to lead to intracellular accumulation of fluorescent porphyrins in high grade malignant gliomas in the brain. On imaging, this accumulation of fluorescent porphyrins helps delineate tumor borders, resulting in the surgeon being better able to visualize and thus able to make a complete, or near-complete resection of the tumor.