Solitary Central Nervous System Relapse of Posttransplant Lymphoproliferative Disorder on 18 F-FDG PET/CT.

A 41-year-old woman received stem cell transplant due to acute myeloid leukemia. Six months after the stem cell transplant, the patient experienced monomorphic PTLD (posttransplant lymphoproliferative disorder) and underwent chemotherapy. Postchemotherapy PET/CT did not show any abnormal 18 F-FDG accumulation in the scanned body, including brain. Four months later, she presented with nausea and vomiting. Brain MRI showed a lesion in the right temporal lobe. In addition to the abnormal 18 F-FDG accumulation in the brain, no other abnormal foci were noted in the torso PET/CT. Biopsy pathology confirmed the diagnosis of monomorphic PTLD.