Primary Intramedullary Spinal Cord Lymphoma Presenting as a Longitudinal Extensive Transverse Myelitis Diagnosed via Brain Biopsy: A Case Report.

Introduction: Primary intramedullary spinal cord lymphoma (PISCL) is a significantly rare condition, accounting for <1% of all central nervous system lymphomas. PISCL has nonspecific clinical and radiological features that often mimic other inflammatory or demyelinating disorders. Thus, it remains challenging to diagnose. Case Presentation: Herein, we report a 61-year-old male patient who initially presented with longitudinally extensive transverse myelitis. During the clinical course, the patient developed cerebral lesions. Despite yielding negative skin and bone marrow biopsy results, a definitive diagnosis of malignant lymphoma was ultimately established via brain biopsy. Conclusion: This case highlights the importance of considering PISCL in the differential diagnosis of acute myelitis, particularly in patients who respond poorly to immunomodulatory therapy or those who experience clinical recurrence. A comprehensive systemic evaluation, including serial brain imaging, is important in PISCL. In cases where abnormalities are detected, prompt and aggressive biopsy should be performed. Early diagnosis and timely initiation of appropriate therapy are essential for improving outcomes in patients with PISCL.