Primary cauda equina lymphoma: case report and literature review.

The central nervous system, in particular the spinal cord, is a rare site for primary lymphoma occurrence, with very few published cases. We report an extremely rare primary lymphoma in the cauda equina in a single case with literature review. An immunocompetent 59-year-old male, who complained of progressive low back and bilateral leg pain for 7 months, was studied. Magnetic resonance imaging (MRI) revealed an intradural space-occupying lesion from T12 to S1, poorly demarcated to the normal cauda equina. The intradural lesion showed T1 low intensity, T2 low isointensity, and marked homogeneous enhancement with gadolinium-diethylenetriaminepentaacetic acid on MRI. We performed spinal tap to obtain additional information about the intradural lesion. Large-sized atypical lymphoid cells were found during pathological examination. Fluorodeoxyglucose accumulation was found only in the lumbar area, which corresponded with the MRI findings, and the primary lymphoma site was defined as the cauda equina area. For further detailed pathological diagnosis, we performed surgical biopsy of the cauda equina. Morphological and immunohistochemical assessment made a diagnosis of diffuse large B-cell lymphoma of the cauda equina. The patient received radiotherapy to the lumbosacral area (50 Gy) and methotrexate (MTX) therapy after surgery. The patient was able to walk without help after the therapies. Follow-up MRI performed 1 year after biopsy showed remission of the lesion. MRI and spinal tap were effective tools for the early definitive diagnosis of cauda equina lymphoma. Combined treatment with radiotherapy and MTX should be performed as early as possible.