Increased Uptake of 18F-THK5351 in Isocitrate Dehydrogenase-Wildtype Glioblastoma But Not in Meningioma

18 F-THK5351 demonstrates a strong binding affinity and selectivity for tau. However, off-target binding with monoamine oxidase-B enzyme, highly expressed in the outer mitochondrial membranes of astrocytes, is possible. In a case with isocitrate dehydrogenase-wildtype glioblastoma, 11 C-MET PET and 18 F-THK5351 PET exhibited increased uptake in the tumor. Conversely, in another case with intracranial meningioma, MET PET revealed increased uptake in the tumor, whereas 18 F-THK5351 PET showed no abnormal uptake in the tumor. However, it is challenging to distinguish meningiomas from glioblastomas on MRI. 18 F-THK5351 PET might help differentiate between isocitrate dehydrogenase-wildtype glioblastoma and meningioma.