BACKGROUND: Needle biopsy is a routinely, relatively safe, and effective tool for patients with brain tumors not suitable for surgical resection. Despite technical advancements, missed diagnosis is still reported in up to 24% of cases. The aim of this study is to investigate the role of sodium fluorescein (NaFL), a cheap and safe fluorophore, in the biopsy setting mainly with the perspective of an enhancement of the sampling accuracy.METHODS: Between January 2018 and March 2020, we prospectively enrolled 48 consecutive patients with suspicion of high-grade glioma to receive NaFL-guided brain tumor biopsy. We compared results between NaFL-group and our historical cohort of patients that underwent biopsy without any dye administration (N.=58). RESULTS: In the NaFL-guided biopsy group, there was a statistically significant increase in diagnostic accuracy compared to the historical cohort (100% vs. 86.2%, P<0.05). The mean number of samples was significantly reduced, (3.3 instead of 4.4 of the control group, P<0.05). Differences in terms of complications related to the procedure, hospital stay, and surgical time were not significant (P=0.49).CONCLUSIONS: To the authors' knowledge, this is the largest published series supporting the usefulness of NaFL during biopsy procedure, with improved diagnostic accuracy. This also allows a reduction in the number of samples needed for diagnosis, and subsequent risks of procedure-related complications, without adding risks related to the drug itself.(Cite this article as: Narducci A, Ronchetti G, Minardi M, Vercelli GG, Nunziata R, Carlino CF, et al. Sodium fluorescein application in brain tumor biopsy. J Neurosurg Sci 2023;67:439-45. DOI: 10.23736/S0390-5616.21.05291-7)