Cutaneous Schwannomas in 22 Horses

Schwannomas are uncommonly recognized in horses. This study describes cutaneous schwannomas in 22 horses aged 8 to 25 years: 12 male, 7 female, and 3 of unknown sex. The horses had solitary cutaneous masses: 9 on the head, 3 on the neck, and the others on the shoulder, hip, thorax, abdomen, rump, ex...

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Bibliographic Details
Published in:Veterinary Pathology 2011-03, Vol.48 (2), p.433-442
Main Authors: Schöniger, S., Valentine, B. A., Fernandez, C. J., Summers, B. A.
Format: Article
Language:English
Subjects:
Animals
Female
Glial Fibrillary Acidic Protein - metabolism
Horse Diseases - pathology
Horses
Immunohistochemistry - veterinary
Laminin - metabolism
Male
Microscopy, Electron, Transmission - veterinary
Neurilemmoma - pathology
Neurilemmoma - veterinary
Skin Neoplasms - pathology
Skin Neoplasms - veterinary
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Summary:Schwannomas are uncommonly recognized in horses. This study describes cutaneous schwannomas in 22 horses aged 8 to 25 years: 12 male, 7 female, and 3 of unknown sex. The horses had solitary cutaneous masses: 9 on the head, 3 on the neck, and the others on the shoulder, hip, thorax, abdomen, rump, extremities, or tail. The location of 1 tumor was unknown. The dermal tumors were well demarcated and expansile. Twelve had a multinodular pattern, whereas 10 formed a single nodule. Antoni A areas were observed in all tumors, and 10 tumors contained Antoni B areas. In Antoni A areas, the densely packed spindle-shaped neoplastic cells were arranged in short fascicles with nuclear palisading. In the hypocellular Antoni B areas, neoplastic cells were separated by abundant myxomatous stroma. Tumors commonly had hyalinization of stroma and vessel walls and ancient change. Cellular vacuolation was observed in 18 tumors. In all 22 cases, neoplastic cells were immunopositive for S100 protein. Expression of laminin and glial fibrillary acidic protein was observed in all 6 tumors evaluated by immunohistochemistry for these markers. One tumor was examined ultrastructurally: Neoplastic cells had branched cytoplasmic processes and were surrounded by an external lamina. Follow-up information was available 8 months to 10 years postexcision for 9 horses, for which surgical excision of the tumor was curative. The equine cutaneous schwannomas in this study had microscopic features like those of human schwannoma and had benign clinical behavior. Correct classification of equine cutaneous schwannoma will facilitate accurate prognosis and appropriate treatment.
ISSN:0300-9858
1544-2217
DOI:10.1177/0300985810377072