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Home / Equine Research Bank / Vet Ophthalmol / Equine Corneal Stromal Invasive Squamous Cell Carcinoma: Cli...
Veterinary ophthalmology2026; 29(2); e70158; doi: 10.1111/vop.70158

Equine Corneal Stromal Invasive Squamous Cell Carcinoma: Clinical and in Vivo Confocal Microscopic Features of 7 Cases.

Abstract: To describe the clinical and in vivo confocal microscopy (IVCM) characteristics of horses with corneal stromal invasive squamous cell carcinoma (CSI-SCC). Methods: Retrospective study of 7 horses with histopathologically confirmed unilateral CSI-SCC. Methods: Horses with corneal CSI-SCC were examined by laser scanning IVCM. Signalment, clinical findings, and histopathology results were compared with IVCM findings. Results: Clinical ocular lesions in all horses included a heavily vascularized, opaque, gray or tan, anterior or midstromal opacity invading the cornea from the limbus. The corneal epithelium overlying the stromal opacities was intact and the abnormal corneal regions were markedly thickened. Crystalline, white, linear, branching stromal opacities emanated from the leading edge of the corneal lesions in 2 horses. Polygonal neoplastic epithelial cells, with prominent anisocytosis and pleomorphism, were visible in the corneal stroma by IVCM and appeared enlarged and hyperreflective. Islands and cords of neoplastic epithelial cells that occasionally branched could be followed by IVCM as they transversed the corneal stroma. The islands of neoplastic cells were occasionally arranged as circular whirls of cells grouped around concentric layers of hyperreflective cells or amorphous materials within a dark cyst-like space consistent with keratin pearls. Dense accumulations of blood vessels and leukocytes were present within and around the neoplastic cells. Conclusions: This report demonstrates the unique ability of IVCM examination to provide a rapid and noninvasive method for the presumptive diagnosis of CSI-SCC and to contribute to the formulation of diagnostic and therapeutic clinical plans for individual horses.
© 2026 American College of Veterinary Ophthalmologists.
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Publication Date: 2026-02-24 PubMed ID: 41732819DOI: 10.1111/vop.70158Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Equine corneal stromal invasive squamous cell carcinoma (CSI-SCC) is characterized by specific clinical features and distinct cellular patterns visible through in vivo confocal microscopy (IVCM), which offers a rapid, noninvasive method to assist diagnosis and treatment planning in affected horses.

Objective of the Study

  • To describe the clinical signs and in vivo confocal microscopic (IVCM) features of horses diagnosed with corneal stromal invasive squamous cell carcinoma (CSI-SCC).
  • To compare clinical findings and histopathological results with IVCM observations in affected horses.

Methods

  • A retrospective study involving 7 horses with histopathologically confirmed unilateral CSI-SCC.
  • Each horse underwent examination using laser scanning in vivo confocal microscopy, which allows detailed visualization of corneal cellular structures.
  • Clinical data, including signalment and ocular examination findings, were collected and compared to microscopic imaging and histopathology results.

Clinical Findings

  • All affected horses had unilateral corneal lesions characterized by:
    • Marked vascularization (increased blood vessel growth within the cornea).
    • Opaque areas that were gray or tan and located in the anterior or mid-stromal (middle layer) region of the cornea.
    • Lesions invading the corneal tissue originating from the limbus (the junction between the cornea and the sclera).
    • An intact corneal epithelium (the outermost corneal layer was not broken or ulcerated).
    • Noticeable thickening of affected corneal regions.
    • In two cases, the presence of crystalline, white, linear, and branching stromal opacities radiating from the lesion edges.

IVCM Observations

  • Neoplastic epithelial cells within the corneal stroma were identifiable by:
    • Polygonal (many-sided) shape.
    • Prominent anisocytosis (variation in cell sizes) and pleomorphism (variation in cell shape).
    • Enlarged size and increased reflectivity suggesting abnormal, neoplastic transformation.
  • Neoplastic epithelial cells appeared in:
    • Islands and cords, some of which branched as they extended through the corneal stroma.
    • Occasionally arranged in circular whorls surrounded by concentric layers of hyperreflective cells or amorphous material within dark cyst-like spaces, consistent with keratin pearls (a hallmark of squamous cell carcinoma).
  • Dense accumulation of new blood vessels and leukocytes (white blood cells) were observed around and within the neoplastic cell aggregates, indicating inflammation and neovascularization associated with the tumor.

Conclusions

  • IVCM is shown to be a highly valuable diagnostic tool for identifying CSI-SCC in horses noninvasively and rapidly.
  • This diagnostic technique reveals characteristic cell morphology and tumor architecture that correlate with histopathological findings.
  • IVCM can aid veterinarians in forming appropriate diagnostic and treatment plans tailored to the individual horse.
  • The study highlights the importance of differentiating CSI-SCC from other corneal opacities using advanced imaging techniques to improve clinical outcomes.

Cite This Article

APA
Ledbetter EC, Knickelbein KE, Irby NL, Schmidt C. (2026). Equine Corneal Stromal Invasive Squamous Cell Carcinoma: Clinical and in Vivo Confocal Microscopic Features of 7 Cases. Vet Ophthalmol, 29(2), e70158. https://doi.org/10.1111/vop.70158

Publication

Veterinary ophthalmology
ISSN: 1463-5224
NlmUniqueID: 100887377
Country: England
Language: English
Volume: 29
Issue: 2
Pages: e70158

Researcher Affiliations

Ledbetter, Eric C
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Knickelbein, Kelly E
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Irby, Nita L
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Schmidt, Corey
  • Veterinary Eye Specialists, Thornwood, New York, USA.

MeSH Terms

  • Animals
  • Horses
  • Horse Diseases / pathology
  • Horse Diseases / diagnostic imaging
  • Carcinoma, Squamous Cell / veterinary
  • Carcinoma, Squamous Cell / pathology
  • Eye Neoplasms / veterinary
  • Eye Neoplasms / pathology
  • Microscopy, Confocal / veterinary
  • Retrospective Studies
  • Female
  • Male
  • Corneal Stroma / pathology
  • Corneal Diseases / pathology
  • Corneal Diseases / veterinary

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