Malignant lymphoma originating in the cauda equina mimicking the inflammatory polyradiculoneuropathy.

A 67-year-old woman was diagnosed with inflammatory polyradiculoneuropathy. The intravenously administered immunoglobulin (IVIG) treatment that she received several times over a 3-year period relieved her clinical symptoms of muscle weakness and sensory disturbances, but these symptoms had worsened thereafter despite further IVIG treatment. MRI detected a solid tumor involving the cauda equina and pathological examinations confirmed this to be malignant lymphoma. The clinical and radiological findings for the malignant lymphoma of the cauda equina in this patient were quite similar to those for the inflammatory polyradiculoneuropathy.