Sacral nerve root neurolymphomatosis diagnosed on FDG-PET/CT and magnetic resonance imaging.

A 67-year-old male with transformed diffuse large B cell lymphoma presented with severe neuropathic-type pain radiating down his posterior right thigh. Initial lumbar radiographs and MRI of the lumbar spine failed to identify a cause for his symptoms. A FDG-PET/CT scan demonstrated increased focal FDG uptake in the right sacral (S2) nerve root. Review of the lumbar spine MRI performed 6 days earlier demonstrated abnormal right S2 nerve root enhancement. The combined FDG-PET/CT and MRI findings allowed a presumptive diagnosis of neurolymphomatosis. However, the patient succumbed to his illness before planned local radiotherapy could be performed.