Surgical management of a progressive iris melanocytoma in a Mustang.
Abstract: A 7-year-old gray Mustang gelding weighing 454 kg was presented for evaluation of a brown mass within the left eye (OS) of 1 year's duration with recent enlargement. Results: A nonpainful, 8 mm diameter, brown, vascularized mass was identified in the anterior chamber of the OS. Ocular B-scan ultrasound confirmed iris involvement and corneal endothelial contact. Histopathology confirmed the presumptive diagnosis of a uveal melanocytic neoplasm, and revealed 1-3 mitotic figures per high power (400x) field. Results: The mass was removed via sector iridectomy without complications, but without complete margins. Three cutaneous melanocytomas noted 1.5 months postoperatively were completely excised. No tumor regrowth was noted 15 months postoperatively, supporting a diagnosis of melanocytoma for the iridal mass. Conclusions: Sector iridectomy is a reasonable treatment option for uncomplicated iridal melanocytomas in horses. Mitotic index and presence of cutaneous melanocytic neoplasms may be irrelevant to the prognosis of equine iridal melanocytic neoplasms.
Publication Date: 2008-02-28 PubMed ID: 18302571DOI: 10.1111/j.1463-5224.2008.00603.xGoogle Scholar: Lookup
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Summary
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This research investigates the cause and treatment of an uncommon eye tumor in a horse. The team surgically removed the growth, and no signs of recurrence were observed post-surgery, making surgical removal a plausible treatment method.
Introduction
- The research focuses on a 7-year-old Mustang gelding (a castrated male horse) that was examined due to a brown mass in its left eye which had been present for a year, with recent enlargement.
- An 8 mm brown and vascularized mass was found in the anterior chamber (front part) of the horse’s eye, which was not causing any pain to the horse.
Methodology and Findings
- A B-scan ultrasound, a diagnostic procedure, was used to verify that the iris (the colored part of the eye) was affected, and that the mass was in contact with the corneal endothelium (the inner layer of the cornea).
- Upon further examination via histopathology (the microscopic examination of tissues), it was confirmed that the mass was actually a type of uveal melanocytic tumor, and the researchers found 1-3 mitotic (dividing) cells per high power field, an indicator of cell proliferation.
- The tumor was removed surgically through a process known as sector iridectomy, which is the removal of a portion of the iris, without any complications arising from the surgery. However, the tumor could not be removed completely due to its position and size.
Postoperative Observations
- A postoperative examination 1.5 months later found three skin melanocytomas (benign melanocytic tumors), which were also fully excised.
- No re-growth of the tumor was detected 15 months after the operation, further confirming the diagnosis of the initial eye tumor as a melanocytoma.
Conclusion
- The study concludes that sector iridectomy is an effective treatment for uncomplicated iridal melanocytomas in horses.
- It also suggests that the mitotic index (rate of cell division) and presence of skin melanocytic tumors do not affect the prognosis of eye melanocytic tumors in horses.
Cite This Article
APA
Scotty NC, Barrie KB, Brooks DE, Taylor D.
(2008).
Surgical management of a progressive iris melanocytoma in a Mustang.
Vet Ophthalmol, 11(2), 75-80.
https://doi.org/10.1111/j.1463-5224.2008.00603.x Publication
Researcher Affiliations
- University of Minnesota Veterinary Medical Center, 1365 Gortner Ave., Saint Paul, MN 55108, USA. scott592@umn.edu
MeSH Terms
- Animals
- Anterior Eye Segment / pathology
- Anterior Eye Segment / surgery
- Horse Diseases / pathology
- Horse Diseases / surgery
- Horses
- Iridectomy / methods
- Iridectomy / veterinary
- Iris Neoplasms / pathology
- Iris Neoplasms / surgery
- Iris Neoplasms / veterinary
- Male
- Nevus, Pigmented / pathology
- Nevus, Pigmented / surgery
- Nevus, Pigmented / veterinary
- Treatment Outcome
Citations
This article has been cited 6 times.- Ostendarp C, Barton AK. Intraocular Tumors in Horses: Diagnosis, Tumor Classification, Oncologic Assessment and Therapy. Vet Sci 2025 Oct 17;12(10).
- Hefner EM, Stoppini R, McMullen RJ Jr. Treatment of Iris Hypoplasia Using Semiconductor Diode Laser in the Horse Under Standing Sedation. Case Rep Vet Med 2025;2025:4021047.
- Labelle AL, Gemensky Metzler AM, McMullen RJ Jr, Wiggans KT, Labelle P, Hamor RE. Equine intraocular melanocytic neoplasia. Can Vet J 2024 Oct;65(10):1048-1054.
- Dufour VL, Cohen JA, Assenmacher CA, Holle DM, Durham AC, Aguirre GD, Miyadera K. Clinical descriptive and long-term outcome of melanocytic uveal lesions in young dogs: 40 cases (45 eyes) including 13 cases of sector iridectomy. Vet Ophthalmol 2025 Mar;28(2):371-385.
- Pereira R, Gillespie S, Rapezzano G, Withers J, Duz M, Foote A. Extensive intraocular melanoma with secondary glaucoma in a 15-month-old Thoroughbred filly. Vet Med Sci 2024 May;10(3):e1471.
- Stas EKL, Hermans H, Slenter IJM, Veraa S, Ensink JM. Noninvasive diode laser-an effective and safe treatment of iris cysts in 46 eyes of 35 horses. Equine Vet J 2023 Mar;55(2):205-213.
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