Multiple masses in a horse's tongue resulting from an atypical perineurial cell proliferative disorder.
Authors: Vashisht K, Rock R W, Summers B A
Journal: Veterinary pathology
Summary
# Editorial Summary A 5-year-old National Show horse presented with progressive lingual masses along the left dorsolateral tongue over a two-year period, prompting investigation into a previously unreported pathological condition. Histopathological and ultrastructural examination revealed elongated mesenchymal cells arranged in concentric whorls around both myelinated and unmyelinated nerve fibres, with immunolabelling confirming a perineurial origin (vimentin-positive, S-100 negative) rather than a schwannoma or other common nerve sheath tumour. The distinctive ultrastructural features—including concentrically laminated cell processes, discontinuous external basal laminae, and abundant pinocytotic vesicles—enabled accurate phenotyping of this proliferative disorder, though the authors could not definitively establish whether the lesion represented a true neoplasm or an atypical hyperplastic process. For equine practitioners, this case highlights the diagnostic challenge of distinguishing uncommon perineurial proliferations from conventional nerve sheath neoplasms, particularly when multiple coalescing masses develop over extended timeframes. Awareness of this condition may prove valuable when encountering recurrent or progressive tongue masses in horses, as morphological and immunohistochemical profiling can guide appropriate classification and management decisions.
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Practical Takeaways
- •Unusual tongue masses in horses warrant detailed pathological examination including immunohistochemistry and electron microscopy to establish diagnosis, as this disorder may not fit standard neoplastic classifications.
- •Progressive, multi-focal tongue masses should prompt investigation for perineurial proliferative disorders, which may be amenable to surgical management.
- •This case expands the differential diagnosis for equine tongue pathology and demonstrates the value of ultrastructural analysis in characterizing rare mesenchymal proliferations.
Key Findings
- •A 5-year-old mare developed progressive, coalescing masses on the tongue over 2 years composed of fusiform mesenchymal cells wrapped around nerves.
- •Histological and ultrastructural analysis identified the masses as perineurial cell proliferation with vimentin-positive, S-100 negative immunophenotype.
- •The proliferative disorder's neoplastic versus non-neoplastic nature remained undetermined despite detailed pathological examination.