A 57-year-old woman with a history of multiple sclerosis presented with a 5-day history of progressive headache and confusion, followed by left hemiparesis. The patient had stopped her previous fingolimod usage during the last 8 weeks. Brain MRI and 18F-FDG PET showed a subcortical tumefactive lesion with an intense peripheric rim of hypermetabolism and central hypometabolism, with central hyperintensity, thin isointense rim, and peripheral finger-like "tentacles" of edema with an irregular and thick border enhancement on postcontrast T2-weighted MRI. Brain biopsy showed features suggestive of relapsing MS. The patient improved after methylprednisone and plasma exchange.