Cutaneous schwannomas in 22 horses.
Authors: Schöniger S, Valentine B A, Fernandez C J, Summers B A
Journal: Veterinary pathology
Summary
# Editorial Summary: Cutaneous Schwannomas in Horses Schwannomas are rare benign nerve sheath tumours that have been poorly characterised in equine practice, yet this histopathological study of 22 cases across eight to 25-year-old horses reveals they present as solitary, well-demarcated dermal masses most commonly on the head and neck, with multinodular architecture in over half the cases examined. The tumours showed classic morphological features including Antoni A areas (densely packed spindle cells with nuclear palisading) and Antoni B areas (hypocellular myxomatous zones), with all 22 cases demonstrating S100 protein immunopositivity—the defining marker for schwannoma diagnosis. Long-term follow-up data from nine horses spanning eight months to ten years post-excision demonstrated that surgical removal was curative in all cases, establishing these tumours as benign with excellent prognosis. For equine practitioners, accurate histological identification is critical because schwannomas' benign nature and excellent response to complete surgical excision distinguish them from other cutaneous neoplasms requiring more aggressive intervention; misclassification may lead to unnecessary treatment or inappropriate prognostication. Clinicians encountering solitary, slow-growing cutaneous masses, particularly in middle-aged to geriatric horses, should consider schwannoma in their differential diagnoses and advocate for histopathological confirmation to guide optimal management.
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Practical Takeaways
- •Solitary cutaneous masses on the head, neck, and body in adult horses may be schwannomas — surgical excision offers a definitive cure with minimal recurrence risk
- •These are benign tumors despite being neoplastic, so complete removal is the appropriate treatment strategy with excellent long-term prognosis
- •Correct histopathological classification (including S100 immunostaining) is important for accurate prognosis and to distinguish schwannomas from other dermal tumors
Key Findings
- •Cutaneous schwannomas occurred in 22 horses aged 8-25 years, most commonly on the head (n=9) and neck (n=3)
- •All 22 tumors were immunopositive for S100 protein, with Antoni A and B histological patterns present in variable proportions
- •Surgical excision was curative in all 9 horses with follow-up data spanning 8 months to 10 years
- •Equine cutaneous schwannomas demonstrated benign clinical behavior with microscopic features consistent with human schwannoma