Fluciclovine-PET Uptake in Microcystic Meningioma Mimicking High-grade Glioma: A Case Report

A 69-year-old asymptomatic woman underwent magnetic resonance imaging (MRI), revealing a left parietal lobe tumor suspected to be a high-grade glioma (HGG). [ 18 F]Fluciclovine-positron emission tomography (PET), which reflects amino acid metabolism, showed moderate uptake [SUVmax 1.4, tumor-to-normal ratio (TNR) 1.9], consistent with HGG, whereas [ 18 F]fluorodeoxyglucose-PET findings demonstrated low uptake (SUVmax 2.5, TNR 0.22), which is atypical for HGG. Surgical and pathologic investigations confirmed the diagnosis of microcystic meningioma, a rare subtype classified as grade 1. Microcystic meningiomas mimic HGG on magnetic resonance imaging and [ 18 F]fluciclovine-PET due to l -amino acid transporter expression, complicating diagnosis.