Introduction Central nervous system (CNS) lymphoma is a very rare form of extranodal non-Hodgkin lymphoma. Lymphomas in the cauda equina region are even rarer. Immunocompromised patients are at high risk for its development. Because of the uncommonness of the disease and unspecific clinical signs and symptoms, the diagnosis and management are aggravated. We present clinical and histopatological findings of a rare metastatic cauda equina lymphoma. Materials and Methods A 57-year-old lady presented with 1 month of severe sciatica, bladder and bowel dysfunction, and motor and sensory disturbances in the inner parts of both thighs (mild motor weakness with limited range of left dorsal flexion, light touch, and pin prick sensations were diminished in the L1-S3 dermatomes on the left side with saddle anesthesia and affected sphincter control). The working diagnosis was a herniated lumbar disc at L5-S1 level, compressing the conus medullaris or cauda equina. On the contrary, MRI of the lumbar spine revealed a tumorous lesion at the level of L5 to S2 on the left side of the spinal cord with compression of the neural structures. No clear differentiation of extradural or intradural location of the lesion was possible. The mass showed marked and homogenous enhancement after intravenous application of gadolinium. No disc pathology was found. The intradural formation was radiologically classified as intradural metastasis. Results A classical laminectomy was performed from first to third sacral vertebra. A soft, bluish violet tumorous mass, lying predominantly extradurally, enchasing the spinal roots of L5 to S2 levels on the left side was found. The dura was infiltrated with the tumor, which was enchasing also the spinal nerve roots. The mass was removed as much as possible, in order not to additionally damage the nervous tissue. After the operation, the nervous status showed improvement of the left leg pain without improvement of neurological deficits. The frozen section showed leukemic infiltration or possibly primary cell B-type lymphoma, as was later confirmed during the definitive histological examination. A lesion was later found also retroperitoneally enchasing the left kidney. The disease was then classified as disseminated extranodal lymphoma, stage 4. After oncological treatment, resolution of the lesions and clinical improvement was documented. Conclusion The CNS is rarely affected by non-Hodgkin lymphoma, except in the late phase of widely disseminated disease. Especially the immunocompromised patients are at risk for its development. Therefore, the extradural non-Hodgkin lymphoma should be considered in the differential diagnosis of spinal cord and root compression. The treatment is tissue biopsy for diagnosis to avoid the nervous damage, followed by chemotherapy and irradiation. Glucocorticoid treatment may temporarily improve the symptoms but on the contrary may obscure the diagnosis. Disclosure of Interest None declared References Knopp EA, Chynn KY, Hughes J. Primary lymphoma of the cauda equina: myelographic, CT myelographic, and MR appearance. AJNR Am J Neuroradiol 1994;15(6):1187–1189 Shen WC, Lee SK, Ho YJ, Lee KR. Myelography, CT and MRI in leukaemic infiltration of the lumbar theca. Neuroradiology 1993;35(7):516–517 Mandawat A, Alraies MC, Miller K, Ondrejka S, Smith S. Cauda equina lymphoma: a case report including postmortem examination. Clin Adv Hematol Oncol 2011;9(5):414–418