[Cauda equina syndrome as the first presentation of intravascular large B-cell lymphoma: a lung biopsy case].

A 65-year-old male was admitted for bladder and rectal dysfunction with lower-limb sensory disturbance. Although no abnormalities were detected on magnetic resonance imaging of the brain and spinal cord, an elevation in the serum anti-cytomegalovirus (CMV) -IgM level and pneumonia suggest viral meningomyelitis. However, steroid pulse and anti-CMV treatments did not resolve the patients' symptoms. Lung and skin biopsies revealed an invasion of atypical lymphoid cells into small vessels, consistent with intravascular large B-cell lymphoma (IVLBCL). Chemotherapy comprising R-CHOP and intrathecal administration of methotrexate resolved neurological complications quickly, and the patient remains in complete remission after 2 years. Notably, IVLBCL with cauda equina syndrome is highly rare.