Evaluation of the Therapeutic Response and Recurrence by 18 F-FLT PET in a Case of Central Nervous System-Lymphomatoid Granulomatosis.

A 78-year-old man visited our hospital complaining of cognitive decline and gait disturbance. MRI revealed multiple nodular enhancing lesions in the brain. He was pathologically diagnosed with central nervous system-lymphomatoid granulomatosis (CNS-LYG) by brain biopsy. Brain PET examinations using 18 F-fluorothymidine (FLT) PET and 11 C-methionine (MET) PET were performed. Strong accumulation in the lesions was observed with 18 F-FLT PET. After treatment, the accumulation of lesions disappeared, and accumulation was observed again at the time of recurrence. In contrast, 11 C-MET PET showed unclear accumulation in the lesions both before therapy and at recurrence. 18 F-FLT uptake was likely reflecting the degree of cell infiltration and the disrupted blood-brain barrier. 18 F-FLT PET might be a useful tool for evaluating the therapeutic response and recurrence of CNS-LYG.