Utility of [18F]fluciclovine PET/MRI for identifying the optimal biopsy target region, helping to avoid underdiagnosis in patients with glioblastoma: illustrative case.

Background: Glioblastoma (GBM) is known for its significant intratumoral heterogeneity, making biopsies susceptible to underdiagnosis if samples are taken from less malignant regions. [18F]Fluciclovine, a novel PET tracer, has demonstrated high accumulation in glioma tissue, with minimal uptake in normal brain tissue.

Observations: A 50-year-old woman presented with sensory aphasia. MRI revealed a FLAIR lesion extending from the left parietal to the medial temporal lobe. [18F]Fluciclovine PET/MRI identified two areas of increased uptake, both FLAIR negative. Stereotactic biopsy was used to obtain samples from PET-positive (PET+) and FLAIR-positive (FLAIR+) lesions. Pathological analysis of the PET+ lesion revealed densely proliferating tumor cells with irregularly enlarged nuclei, while the FLAIR+ lesion exhibited sparsely proliferating cells. Molecular analysis showed that both lesions were IDH wildtype with MGMT promoter hypomethylation. Sanger sequencing identified a telomerase reverse transcriptase promoter -124 C>T mutation in the PET+ lesion but not in the FLAIR+ lesion. The integrated diagnosis, based primarily on the PET+ lesion, was GBM, IDH wildtype.

Lessons: This case highlights the importance of [18F]fluciclovine PET/MRI in identifying high-cell-density regions, minimizing the risk of underdiagnosis in GBM. Further studies are necessary to evaluate its prognostic value in GBM management. https://thejns.org/doi/10.3171/CASE24677.