Unexpected [18F] Fluciclovine Uptake in Pilocytic Astrocytoma: A Pediatric Case Report

A 5-year-old asymptomatic boy underwent MRI, which revealed a mass lesion in the septum pellucidum suspected to be a glioma. [18F]Fluciclovine PET, which provides insight into amino acid metabolism, revealed high uptake (SUVmax, 2.37; TBR, 3.56), which was consistent with high-grade glioma. In contrast, [18F] Fluorodeoxyglucose PET showed low uptake (SUV max: 2.2; TBR: 0.29). Partial resection and histopathology confirmed pilocytic astrocytoma, a WHO grade 1 tumor, with KIAA1549-BRAF fusion. High [18F] Fluciclovine uptake in pilocytic astrocytoma may reflect amino acid transporter expression, which may lead to overestimation of the WHO grade. Awareness of this pitfall is essential in pediatric neuro-oncology.