Corneal Squamous Cell Carcinoma Arising From a Conjunctival Graft Scar in a Horse.
Abstract: To describe the case details of an equine corneal squamous cell carcinoma (SCC) arising from the central scar of a previous conjunctival pedicle graft. Methods: An 18-year-old Thoroughbred gelding, showing a progressive increase in diameter, depth, opacity, and pigmentation of a conjunctival pedicle graft scar of the left eye, 34 months after surgery. Methods: Complete ophthalmic examination, standard histologic and immunohistochemical evaluation of an incisional biopsy to formulate a definitive diagnosis. Carbon dioxide (CO) laser photoablation combined with topical mitomycin C treatment. Results: Initial examination with slit-lamp biomicroscopic examination revealed a raised, pale pink and peripherally pigmented, ovoid corneal mass (25 × 20 mm, raised 5 mm) with a smooth to cobblestone contour, paraxial ventral at 6 o'clock of the left eye. Corneal neovascularization extended from the ventral limbus to the graft scar. The remaining ophthalmic examination was unremarkable. Histologic and immunohistochemical evaluation of an incisional biopsy were supportive of a diagnosis of corneal SCC. Two rounds of CO laser photoablation, 10 weeks apart, combined with topical mitomycin C chemotherapy, without surgical debulking, was successful in resolving the neoplastic lesion. The horse was euthanized 4 years later for unrelated reasons, with no evidence of SCC recurrence grossly or histologically. Conclusions: To the authors' knowledge, this is the first report in a horse of a SCC developing at the site of corneal scarring after a conjunctival pedicle graft.
© 2025 American College of Veterinary Ophthalmologists.
Publication Date: 2025-10-15 PubMed ID: 41090548DOI: 10.1111/vop.70102Google Scholar: Lookup
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Summary
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Overview
- This study reports a unique case of corneal squamous cell carcinoma (SCC) developing from the scar of a previous conjunctival graft in a horse’s eye.
- The paper describes the diagnosis, treatment using CO2 laser photoablation combined with topical chemotherapy, and long-term outcome of the case.
Background and Case Description
- The subject was an 18-year-old Thoroughbred gelding with a history of conjunctival pedicle graft surgery on the left eye.
- 34 months post-surgery, a progressive lesion appeared at the central scar site of the graft characterized by increased size, depth, opacity, and pigmentation.
- Clinical presentation included a raised, pale pink corneal mass with peripheral pigmentation, approximately 25×20 mm in size and 5 mm thick, located ventrally in the cornea at the 6 o’clock position.
- Corneal neovascularization (new blood vessel formation) extended from the ventral limbus (corneal border) to the graft scar site.
- Other ophthalmic findings were unremarkable, indicating the lesion was localized without additional widespread eye abnormalities.
Diagnostic Approach
- A complete ophthalmic examination was performed using slit-lamp biomicroscopy to visualize the lesion’s characteristics.
- An incisional biopsy of the lesion was obtained for histologic and immunohistochemical analyses to confirm the nature of the tumor.
- Histology and immunohistochemistry supported the diagnosis of corneal squamous cell carcinoma, identifying malignant epithelial cells typical of SCC.
Treatment Methodology
- The treatment approach avoided surgical debulking (cutting out the tumor mass) due to potential complications and instead used minimally invasive techniques.
- Two sessions of carbon dioxide (CO2) laser photoablation were performed 10 weeks apart to vaporize the tumor tissue precisely and minimize damage to surrounding healthy tissue.
- Topical mitomycin C, a chemotherapeutic agent, was applied to the cornea to inhibit tumor cell proliferation and reduce risk of recurrence.
- The combined laser and chemotherapy approach successfully resolved the corneal SCC without the need for more invasive surgery.
Outcome and Follow-up
- The horse was monitored for 4 years after treatment with no clinical or histological evidence of SCC recurrence, indicating a durable remission.
- Eventually, the horse was euthanized for unrelated reasons, and necropsy confirmed absence of tumor regrowth at the treated site.
Significance and Conclusions
- This is the first documented case of corneal SCC arising from a conjunctival graft scar in a horse, highlighting a rare but possible late complication of graft surgery.
- The report demonstrates that non-surgical CO2 laser photoablation combined with topical chemotherapy can be an effective, vision-sparing treatment option for corneal SCC in equine patients.
- The study underscores the importance of long-term monitoring of graft sites for neoplastic transformation especially in species prone to corneal SCC.
- Findings contribute to veterinary ophthalmology knowledge by identifying a novel SCC etiology and a successful minimally invasive treatment protocol.
Cite This Article
APA
du Preez S, Lynch B, Lindsay S, Simon O, Ferlini Agne G.
(2025).
Corneal Squamous Cell Carcinoma Arising From a Conjunctival Graft Scar in a Horse.
Vet Ophthalmol, 29(2).
https://doi.org/10.1111/vop.70102 Publication
Researcher Affiliations
- School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, South Australia, Australia.
- School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, South Australia, Australia.
- School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, South Australia, Australia.
- School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, South Australia, Australia.
- School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, South Australia, Australia.
MeSH Terms
- Animals
- Horses
- Horse Diseases / pathology
- Horse Diseases / etiology
- Horse Diseases / diagnosis
- Horse Diseases / surgery
- Horse Diseases / therapy
- Carcinoma, Squamous Cell / veterinary
- Carcinoma, Squamous Cell / etiology
- Carcinoma, Squamous Cell / pathology
- Carcinoma, Squamous Cell / diagnosis
- Carcinoma, Squamous Cell / therapy
- Eye Neoplasms / veterinary
- Eye Neoplasms / etiology
- Eye Neoplasms / pathology
- Male
- Cicatrix / veterinary
- Cicatrix / complications
- Cicatrix / pathology
- Corneal Diseases / veterinary
- Corneal Diseases / etiology
- Corneal Diseases / pathology
- Mitomycin / therapeutic use
- Conjunctiva / transplantation
- Conjunctiva / pathology
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