The Primary Central Nervous System Lymphoma is an uncommon disease and rarely affects the spinal cord. The authors present the case of a female patient, 67 year-old, with paresis of the left leg. Lumbosacral MRI depicts focal thickening of the cauda equina roots at L2 level, isointense on T1W and hyperintense on T2W with intense contrast enhancement. Immunohistochemistry analysis of a biopsied root confirmed the diagnosis of Diffuse Large B-cell Lymphoma. The PCNSL, generally represented by Large B-cells subtype, affects the spinal cord in less than one per cent of the cases and are generally associated with cytogenetic changes on BCL-6 gene. The appearance on MRI is not characteristic, evidencing the focal volumetric increase of the cauda equina roots, with intense contrast enhancement, being not possible to differentiate between lesions as schwannomas and meningiomas. For the diagnosis is necessary biopsy of the lesion and after intraoperative confirmation, resection should be suspended because it is not effective. The treatment is based on chemotherapy and radiotherapy, however, the prognosis is poor.
