Progressive Multifocal Leukoencephalopathy Mimicking Malignancy on 68Ga-FAPI PET/CT: Potential Advantages of FAPI.

A 43-year-old man presented with weakness in his right upper limb for 2 months. Head MRI showed intracranial multiple abnormal signal foci. Malignancy was suspected. The patient was subsequently enrolled in the clinical trial of 68Ga-FAPI PET/CT. 68Ga-FAPI PET/CT showed intracranial multiple FAPI-avid foci. It was also highly suggestive of malignancy. However, the combination of clinical manifestations, imaging findings, cerebral spinal fluid examinations, and effective immunotherapy confirmed the diagnosis of progressive multifocal leukoencephalopathy. 68Ga-FAPI may have potential advantages in the diagnosis of progressive multifocal leukoencephalopathy.