Spinal Cord Compression in a Horse due to a Granular Cell Variant of Neurofibroma.

This study examines a unique case of a horse with spinal cord compression caused by a rare subtype of neurofibroma. This is the first reported case of such in an animal, shedding light on granular cell differentiation in other peripheral nerve sheath tumors.

Case Presentation and Examination

• The research focuses on a 7-year-old horse who had been displaying ataxia (loss of full control of bodily movements) affecting the forelimbs and hindlimbs for three months. Based on these symptoms, it was suggested that the underlying complication had a C1-C6 neuroanatomical localization.
• Upon investigation following the horse’s death, an intradural mass was found. Positioned on the right sixth cervical spinal nerve, this mass was creating pressure on the spinal cord – a condition known as spinal cord compression.

Investigation into the Intrudural Mass

• The mass was examined histologically and found to be predominantly made up of wavy spindle cells. These spindle cells are a mixture of Schwann cells, perineurial cells, and fibroblasts, closely linked with ropy collagen fibres.
• Around a quarter of these spindle cells were swollen and filled with densely-packed eosinophilic and Periodic Acid-Schiff (PAS)-positive cytoplasmic granules. This description suggests that the horse was suffering from a granular cell form of neurofibroma, something not previously reported in animal cases.

Immunohistochemistry and Cell Labeling

• Immunohistochemistry is a process used to identify cells of various types in tissues. In this study, it was used to highlight some of the neoplastic cells within the mass. The antigens for S100 and Glial Fibrillary Acidic Protein (GFAP) were used, confirming their presence within the neoplastic cells.
• The cytoplasmic granules of the cells within the mass were also proven to be positive for S100 and neuron specific enolase through this method. This further indicated the presence of a granular cell variant of neurofibroma.

Significance and Further Discussion

• This study is significant as it presents the first reported case of a horse, or indeed any animal, suffering from a granular cell form of neurofibroma.
• The report also briefly discusses the phenomenon of granular cell differentiation in other types of peripheral nerve sheath tumors found in animals. This suggests that further investigation into this particular cell differentiation could lead to new understanding and treatment methods for similar conditions in veterinary medicine.