Spinal Cord Medulloepithelioma in a Cat.

A 13-month-old, neutered, male, domestic shorthair cat was referred with a history of progressive paraparesis, proprioceptive ataxia, and lumbar spinal pain. Neurological examination revealed non-ambulatory paraparesis consistent with L4-S1 myelopathy. Magnetic resonance of the thoracolumbar spinal cord identified a dorsal intradural extramedullary space-occupying lesion extending from L5 to L6. It was homogeneously hyperintense in T2-weighted imaging and isointense in T1-weighted imaging and exhibited marked and homogeneous contrast enhancement in the T1-weighted post-contrast imaging. The removed tissue was composed of neoplastic cells arranged as pseudostratified or multilayered trabecular and tubular structures, supported by internal and external limiting PAS-positive membranes. The neoplastic cells were immunoreactive for vimentin and NSE and negative for GFAP, Olig2, synaptophysin, PCK, S-100, NeuN, and nestin. The Ki-67 nuclear labeling index was up to 90%. The tumor was consistent with the diagnosis of medulloepithelioma, which is most frequently reported as an intraocular tumor. The morphological and immunohistochemical features of the tumor showed remarkable concordance with most human medulloepitheliomas. This is the first spinal cord medullopethelioma report in a cat, with the clinical, neuroradiological, histological, and immunohistochemical findings being described.