Extensive intraocular melanoma with secondary glaucoma in a 15-month-old Thoroughbred filly.
Abstract: A 15-month-old, grey, Thoroughbred filly presented for investigation of a 6-week history of corneal oedema and blepharospasm on the right eye (OD). The filly was otherwise healthy. Following ophthalmic examination, glaucoma on the OD was diagnosed. A space occupying mass within the anterior chamber was documented on transpalpebral ultrasonographic examination. This mass obliterated most of the anterior intraocular structures on the peripheral nasal side (corneal endothelium and drainage angle), leading to secondary glaucoma. After systemic and topical treatment addressing secondary glaucoma, the corneal oedema reduced. The mass was visualised as an irregularly rounded brown structure associated with the iris on the peripheral nasal side of the anterior chamber. Given the filly's signalment, location and appearance of the mass, a tentative diagnosis of intraocular melanoma was made and enucleation was performed. Histopathological evaluation of the globe revealed solid sheets of heavily pigmented melanocytic cells, disrupting the normal ciliary body architecture and extending into the iris and subretinal. The cells were pleomorphic, polyhedral to round with occasional spindle-shaped cells, and contained moderate to large amounts of granular black-brown pigment (melanin). The iridal component expanded into the anterior chamber, with cells directly opposed to Descemet's membrane, with loss of the endothelium and expanding and occluding the filtration angle in this area. The lesion infiltrated locally into the edge of the sclera, but did not extend through the sclera, though occasional perivascular clusters of melanophages were observed within the scleral stroma adjacent to the optic nerve. Diagnosis of a uveal melanocytic neoplasm was confirmed, with characteristics similar to only one reported case . This is a unique case of a rapidly growing, invasive, uveal melanoma in a young horse. Intraocular melanoma should be considered as a differential diagnoses for glaucoma in grey horses, regardless of the age and absence of melanocytic skin lesions.
© 2024 The Authors. Veterinary Medicine and Science published by John Wiley & Sons Ltd.
Publication Date: 2024-05-13 PubMed ID: 38739097PubMed Central: PMC11090147DOI: 10.1002/vms3.1471Google Scholar: Lookup
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Summary
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A 15-month-old Thoroughbred filly was diagnosed with an intraocular melanoma causing secondary glaucoma. This is a rare case of such a fast-growing, invasive melanoma within the eye of a young horse.
Background and Presentation
- The filly in question is a 15-month-old, grey Thoroughbred who presented with a 6-week history of corneal oedema and blepharospasm in the right eye (OD), while otherwise being healthy.
Diagnosis and Findings
- Upon examination, the filly was diagnosed to have glaucoma in the right eye.
- An ultrasonographic test revealed a space occupying mass within the anterior chamber of the eye. This mass had obliterated most of the anterior intraocular structures on the peripheral nasal side resulting in secondary glaucoma.
- A post-treatment visualization of this mass showed it to be an irregularly rounded brown structure associated with the iris on the peripheral nasal side of the anterior chamber.
- Given the filly’s history, location and appearance of the mass, a preliminary diagnosis of intraocular melanoma was made and enucleation was performed for further examination.
Further Investigation and In-Depth Analysis
- A histopathological study of the eye revealed pigmented melanocytic cells that disrupted normal ciliary body structure and had extended into the iris and subretinal.
- The cells forming the mass were found to be irregular, varying from polyhedral to round shape, with some being spindle-shaped. They contained moderate to large amounts of granular black-brown pigment, or melanin.
- This growth had expanded into the anterior chamber and had directly affected Descemet’s membrane, causing loss of the endothelium and occluding the filtration angle in that area.
- The growth had locally infiltrated into the edge of the sclera but did not penetrate it. However, clusters of melanophages were observed within the scleral stroma adjacent to the optic nerve.
- This confirmed diagnosis of a uveal melanocytic neoplasm, similar in characteristics to only one previously reported case.
Conclusion
- This represents a unique case of a rapidly growing, invasive uveal melanoma in a young horse. The findings suggest, despite the age and absence of melanocytic skin lesions, intraocular melanoma should be a differential diagnosis for glaucoma in grey horses.
Cite This Article
APA
Pereira R, Gillespie S, Rapezzano G, Withers J, Duz M, Foote A.
(2024).
Extensive intraocular melanoma with secondary glaucoma in a 15-month-old Thoroughbred filly.
Vet Med Sci, 10(3), e1471.
https://doi.org/10.1002/vms3.1471 Publication
Researcher Affiliations
- Pool House Equine Hospital, IVC Evidensia, Staffordshire, UK.
- Little Rock Equine Vets, Staffordshire, UK.
- Pool House Equine Hospital, IVC Evidensia, Staffordshire, UK.
- Pool House Equine Hospital, IVC Evidensia, Staffordshire, UK.
- School of Veterinary Medicine, University of Nottingham, Sutton Bonington, UK.
- Department of Rossdales Laboratories, Rossdales Equine Hospital and Diagnositc Centre, Newmarket, UK.
MeSH Terms
- Animals
- Horses
- Horse Diseases / pathology
- Horse Diseases / surgery
- Glaucoma / veterinary
- Glaucoma / etiology
- Melanoma / veterinary
- Melanoma / surgery
- Female
- Eye Neoplasms / veterinary
- Eye Neoplasms / surgery
Conflict of Interest Statement
The authors declare no conflicts of interest.
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This article includes 19 references
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