Primary Central Nervous System Lymphoma: A Case of Solitary Brain Lesion.

Primary central nervous system lymphoma (PCNSL) is an uncommon variant of extranodal non-Hodgkin's lymphoma (NHL) that involves the brain, leptomeninges, eyes, or spinal cord without evidence of systemic disease. This article presents a case of a 63-year-old Caucasian female with high-grade B-cell lymphoma who was found to have a solitary brain lesion and no distant metastasis upon diagnosis. The patient had left-sided weakness and difficulty standing on presentation and was found to have a right frontal lobe mass with surrounding mild vasogenic edema and a small focal area of hemorrhage concerning for high-grade glioma versus lymphoma on MRI. However, pathology results revealed high-grade B-cell lymphoma. The case reinforces the importance of working up any lesion suspicious for lymphoma/glioma. Diagnosis of high-grade B-cell lymphoma can be difficult based on morphological and cytological appearance due to varying gene expression and presentation at diagnosis. It can closely mimic diffuse B-cell lymphoma. Extensive workup including HIV serology, MRI imaging, evaluation for spinal cord involvement, and lumbar puncture (LP), to rule out cerebrospinal fluid (CSF) involvement, prior to initiating treatment needs to be done. The case also addresses high-grade methotrexate (MTX)-based chemotherapy as a treatment that improves mortality in patients with primary central nervous system (CNS) lymphoma.