Primary Central Nervous System Lymphoma Masquerading as Multiple Sclerosis - A Case Report

Primary central nervous system lymphoma represents a rare and aggressive variant of non-Hodgkin lymphoma that remains confined to the central nervous system without systemic involvement at the time of diagnosis.[1] We present a case of a 48-year-old immunocompetent male who initially received a diagnosis of multiple sclerosis but was subsequently found to harbor PCNSL (Primary Central Nervous System Lymphoma) of the diffuse large B-cell type.[2] This case highlights the considerable clinical and radiological similarities between PCNSL and demyelinating disorders, demonstrating the critical importance of obtaining tissue diagnosis through biopsy and comprehensive immunohistochemical evaluation for accurate diagnosis and timely therapeutic intervention.[1] Primary central nervous system lymphoma accounts for approximately 3.3% of all primary brain tumors. In immunocompetent patients, the vast majority of PCNSL cases originate from germinal center B-cells and develop within the brain parenchyma, spinal cord, cerebrospinal fluid compartment, or intraocular structures without evidence of systemic disease. The diagnosis of PCNSL poses significant challenges due to its non-specific clinical presentation, ambiguous neuroimaging characteristics, and often unrevealing cerebrospinal fluid findings, leading to frequent misdiagnosis. Through this case presentation, we aim to emphasize the importance of including PCNSL in the differential diagnosis when magnetic resonance imaging demonstrates non-enhancing, diffusely infiltrative lesions.[1]