PMC8204169_01
Imaging and pathological findings. Panel A: MRI brain, axial T2 FLAIR sequence, shows mild hyperintensity and thickening of the trigeminal nerve (arrow) without other changes sufficient to cause raised intracranial pressure. Panel B: MRI lumbosacral spine, sagittal T2 sequence, shows a soft tissue density causing complete effacement of the CSF spaces around the lower spinal cord. Panel C: MRI lumbosacral spine, sagittal T1 post-contrast sequence, shows diffuse leptomeningeal enhancement along the surface of the spinal cord and the cauda equina (arrow). Panel D: FDG-PET whole body scans show intense FDG uptake in the spinal column, corresponding to the soft tissue lesions detected on MRI. Panel E: H&E stain at 40x magnification shows sheets of intermediate to large cells with abundant eosinophilic cytoplasm and eccentrically placed nuclei with pale chromatin. Panels F and G: the tissue stained strongly positive for CD4 and CD163, respectively. Panel H: leucocyte common antigen (LCA) stain was weakly positive. This pattern of staining is in keeping with a diagnosis of histiocytic sarcoma. CSF, cerebrospinal fluid; FDG, fluorodeoxyglucose; PET, positron emission tomography.
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F1
An intradural infiltrative process caused complete effacement of the CSF spaces surrounding the cauda equina and conus medullaris (figure 1A, B). The cells were positive for CD68, CD163 and CD4, and negative for T-cell and B-cell markers, thus confirming their histiocytic/monocytic lineage (figure 1E-H).