Central nervous system lymphoma initially diagnosed as tumefactive multiple sclerosis after brain biopsy

Abstract

A 72-year-old man was admitted with left homonymous hemianopsia and hemiparesis. Magnetic resonance imaging revealed a heterogeneously enhanced lesion in the right parietal lobe. A brain biopsy showed acute demyelination without malignancy, which led to a diagnosis of tumefactive multiple sclerosis (MS). The pa-tient received corticosteroid therapy and experienced clinical and radiological improvement. Six months later, new lesions appeared, and a second biopsy revealed proliferation of dysplastic lymphocytes. This led to a re-vised diagnosis of primary central nervous system lymphoma (PCNSL). Because PCNSL mimics MS both clinically and radiologically, PCNSL is difficult to diagnose. Performing repeated brain biopsies may there-fore be required when PCNSL is strongly suspected. © 2013 The Japanese Society of Internal Medicine.