Equine Sarcoid Arising From the Medial Caruncle With Invasion of the Third Eyelid in a Quarter Horse Gelding.
Abstract: To describe the clinical and histologic features of a sarcoid arising from the medial caruncle with spread to the third eyelid of a horse. Methods: A 20-year-old Quarter Horse gelding. Methods: An incisional biopsy of the medial caruncle mass was initially performed, with histopathology suggesting a sarcoid or other spindle cell neoplasm. The mass grew rapidly following the biopsy, expanding to affect the third eyelid and adjacent superior palpebral conjunctiva. A complete third eyelid and medial caruncle excision with resection of affected palpebral conjunctiva and adjunctive cryotherapy was subsequently performed. Results: Histopathology revealed the mass to be consistent with an equine sarcoid as evidenced by a densely cellular population of neoplastic spindle cells arranged into interlacing bundles with collagenous stroma and with hyperplastic overlying epithelium extending into the neoplasm as thin rete ridges. Over 90% of neoplastic cells showed strong hybridization signaling for bovine papillomavirus types 1 and 2, supporting an underlying viral cause consistent with the diagnosis of a sarcoid. Conclusions: This paper describes the first reported case of an equine sarcoid arising from the medial caruncle with spread to the third eyelid, treated with third eyelid and medial caruncle excision and adjunctive cryotherapy. Veterinarians evaluating horses with masses affecting the medial caruncle and third eyelid should consider sarcoids as a differential diagnosis. Rapid growth of cutaneous sarcoids following incisional biopsy is common, and the same may be true for sarcoids that arise from the medial caruncle or third eyelid.
© 2025 American College of Veterinary Ophthalmologists.
Publication Date: 2025-09-04 PubMed ID: 40904264DOI: 10.1111/vop.70074Google Scholar: Lookup
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Summary
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Equine sarcoid, a type of skin tumor linked to bovine papillomavirus, was identified originating from the medial caruncle of a Quarter Horse and invading its third eyelid, with surgical excision and cryotherapy used for treatment.
Background and Objective
- The study focuses on an unusual case of an equine sarcoid, a common skin tumor in horses.
- This sarcoid originated specifically from the medial caruncle, a small anatomical structure at the inner corner of the eye.
- Importantly, the tumor invaded the third eyelid, a protective structure within the horse’s eye.
- The objective was to describe clinical presentation, histologic features, and the treatment approach.
Case Description and Methods
- The subject was a 20-year-old Quarter Horse gelding presenting with a mass on the medial caruncle.
- An incisional biopsy was initially performed for diagnostic purposes.
- Histopathology of the biopsy suggested the tumor might be a sarcoid or another spindle cell neoplasm.
- Following the biopsy, the mass grew rapidly and spread to involve the third eyelid and adjacent conjunctival tissue.
- Definitive treatment involved the surgical removal of the entire third eyelid and medial caruncle along with the affected conjunctiva, combined with adjunctive cryotherapy (freezing treatment) to reduce recurrence risk.
Histopathological Findings
- Microscopic analysis revealed a densely packed population of neoplastic spindle cells arranged in interlacing bundles.
- These cells were embedded within a collagen-rich stroma, a typical feature of sarcoids.
- The overlying epithelium was hyperplastic (thickened) and extended downward into the tumor as thin rete ridges, a hallmark of sarcoid architecture.
- More than 90% of tumor cells showed strong molecular signals for bovine papillomavirus (BPV) types 1 and 2.
- This viral association supports the diagnosis of a sarcoid, as BPV infection is known to play a critical role in sarcoid pathogenesis.
Significance and Clinical Implications
- This case is the first reported instance of an equine sarcoid originating from the medial caruncle and spreading into the third eyelid.
- The findings suggest that when evaluating periocular masses in horses, veterinarians should include sarcoids in their differential diagnoses.
- The rapid growth of the sarcoid following incisional biopsy is consistent with known behavior of cutaneous sarcoids, implying caution in biopsy and treatment planning.
- Effective management combined surgical excision with cryotherapy to prevent recurrence, highlighting a potential treatment protocol for similar cases.
Conclusion
- This report expands the knowledge of sarcoid behavior in horses by documenting an unusual anatomical location and invasive growth pattern.
- The combined surgical and cryotherapeutic approach was successful in addressing the tumor.
- Veterinarians should be aware of sarcoids as a possible cause of masses involving the medial caruncle and third eyelid, especially given the potential for rapid growth after biopsy.
Cite This Article
APA
Plotsker NM, Taylor R, Coffin HR, Beatty A, Newbold G, Knickelbein KE.
(2025).
Equine Sarcoid Arising From the Medial Caruncle With Invasion of the Third Eyelid in a Quarter Horse Gelding.
Vet Ophthalmol, 29(2), e70074.
https://doi.org/10.1111/vop.70074 Publication
Researcher Affiliations
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, USA.
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, USA.
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
MeSH Terms
- Animals
- Horses
- Horse Diseases / pathology
- Horse Diseases / surgery
- Horse Diseases / diagnosis
- Sarcoidosis / veterinary
- Sarcoidosis / pathology
- Sarcoidosis / surgery
- Sarcoidosis / diagnosis
- Male
- Eyelid Neoplasms / veterinary
- Eyelid Neoplasms / pathology
- Eyelid Neoplasms / surgery
- Eyelid Neoplasms / diagnosis
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