The Appearance of Epidural Extranodal Marginal Zone Lymphoma (MALToma) on F-18 FDG PET/CT and Post Hoc PET/MRI Fusion

A 27-year-old woman previously treated for extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALToma) underwent F-18 FDG PET/CT for restaging, which demonstrated intense uptake in the lumbosacral thecal sac and adjoining nerve roots, with subtle increased paraspinal soft tissue. Contrast-enhanced MRI of the spinal cord performed 2 days later confirmed the enhancing lower lumbar and sacral epidural lymphomatous masses with resultant moderate to severe compression of the thecal sac and bilateral neural foraminal stenosis. Post hoc PET/MRI fusion was performed, proving that the enhancing masses on contrast-enhanced MRI were indeed the etiology of the hypermetabolic signal detected on the prior PET/CT. This case serves to illustrate the infrequently encountered, but virtually pathognomonic appearance of epidural involvement of lymphoma, which is easiest to recognize on maximum intensity projection images.