False-positive finding of brain metastasis on (18)F-FDG PET imaging due to early subacute ischemic stroke.

An F-FDG PET performed for staging of a left lung mass showed a hypermetabolic focus in the left posterior fossa suggestive for brain metastasis. However, subsequent MRI showed restricted diffusion in the left cerebellum indicating a subacute ischemic stroke. Follow-up PET showed resolution of FDG uptake; MRI showed focal left cerebellar encephalomalacia. This case demonstrates visualization of the hypermetabolic inflammatory phase of a subacute ischemic stroke. The rare possibility of a false-positive result for brain metastasis must be recognized, and because focal neurologic symptoms may overlap in brain metastases and stroke, MRI confirmation of positive brain findings on FDG PET is needed.