A 64-year-old woman with progressive dementia and leukoencephalopathy.

In a 64-year-old woman presenting with rapidly progressive dementia, brain magnetic resonance imaging revealed a diffuse leukoencephalopathy without gadolinium enhancement, and the 14.3.3 protein was found to be positive in the cerebrospinal fluid. An electroencephalogram showed diffused slow waves and epileptic seizures without periodic paroxysmal activity. The patient died 3 months after onset of symptoms, and an autopsy restricted to the brain was performed. Gross examination was not informative, and only microscopic examination permitted identification of scattered lymphomatous cells on all sections from the brain hemispheres, brain stems and cerebellum. Immunopositivity of these tumor cells for CD20 attested their B phenotype. This observation illustrates "lymphomatosis cerebri," a recently described entity, which has to be considered in the differential diagnosis of rapidly progressive dementia in adults.