18F-THK5351 Positron Emission Tomography Clearly Depicted Progressive Multifocal Leukoencephalopathy after Mantle Cell Lymphoma Treatment.

An 84-year-old Japanese woman presented with left hemiplegia 8 months after completing chemotherapy for mantle cell lymphoma. Brain magnetic resonance imaging (MRI) revealed a hyperintense lesion extending from the right parietal lobe to the left parietal lobe. Compared with these MRI results, 18F-THK5351 PET revealed more extensive accumulation. A brain biopsy showed progressive multifocal leukoencephalopathy (PML). Immunohistochemistry and John Cunningham virus (JCV) DNA-polymerase chain reaction indicated JCV infection. Therefore, a diagnosis of PML was made. 18F-THK5351 PET, indicative of activated astrocytes, clearly depicted PML lesions composed of reactive and atypical astrocytes. 18F-THK5351 PET may capture fresh progressive PML lesions better than MRI.