Abstract
A 75-year-old man presented with cognitive decline, headaches, and ataxic gait. Magnetic resonance imaging (MRI) revealed acute infarcts in multiple brain regions, and vessel wall MRI (VW-MRI) demonstrated concentric arterial wall thickening and enhancement in some intracranial arteries, initially suggesting primary central nervous system vasculitis (PCNSV). Despite immunosuppressive therapy, the patient developed further infarction. A skin biopsy revealed intravascular large B-cell lymphoma (IVLBCL), and autopsy revealed tumor cells in the arterial walls corresponding to the VW-MRI findings. This case highlights the risk of a misdiagnosis of PCNSV based solely on imaging findings and underscores the need for histological confirmation.