5-ALA Fluorescence in Case of Brain Abscess by Aggregatibacter Mimicking Glioblastoma

Background: At present, the differential diagnosis of magnetic resonance imaging enhancing lesions can still be challenging. Preoperative imaging is a valuable tool characterized by high informative value, even if false-positive and false-negative results are possible. In this context, 5-aminolevulenic acid (5-ALA) represents a significant adjunct in glioblastoma (GBM) surgery displaying an assumed specific accumulation only in tumor cells. However, it was anecdotally reported that in some cases it can also be detected in nonneoplastic lesions mimicking GBM, thus potentially leading to misdiagnosis. Moreover, precise identification of involved pathogens from intraoperative brain samples may remain difficult. We report the case of an abscess from Aggregatibacter mimicking a GBM both during preoperative imaging and intraoperatively, since showing 5-ALA fluorescence. Case Description: A 54-year-old man presented with intense cephalalgia, vomiting, and scotomas in his left eye. Brain magnetic resonance imaging demonstrated a right temporo-occipital rim-enhancing mass, highly suggestive of a GBM, and for this reason the patient underwent 5-ALA−guided complete removal. Histopathologic analysis proved the lesion to be a bacterial abscess from Aggregatibacter as confirmed by polymerase chain reaction on bacterial deoxyribonucleic acid. Conclusions: 5-ALA fluorescence may not be specifically involved only in malignant tumor cells, thus raising the suspect for alternative diagnoses to GBM and inviting caution into fluorescence-guided surgery.