Equis ISSN 2398-2977

Eye: neoplasia - melanoma

Contributor(s): Prof Derek Knottenbelt, Paul E Miller, Graham Munroe, Anna Hollis

Introduction

  • Incidence: the most frequently reported primary intra-ocular tumor, usually derived from the anterior uvea. Uncommon eyelid and adnexal tumour except in gray or white coated horses.
  • Signs: slow growing pigmented tumors that do not metastasize; intra-ocular tumors may present with anterior uveitis +/- pupillary distortion +/- corneal edema and ocular pain.
  • Diagnosis: clinical examination, ultrasonographic imaging, biopsy and histopathology.
  • Treatment:
    • Eyelid tumors: surgical excision including blepharoplastic techniques.
    • Intra-ocular tumors: enucleation.
  • Prognosis: guarded.
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Pathogenesis

Etiology

  • Unclear.
  • No evidence of UV light involvement (tumors typically occur in areas not exposed to sunlight).

Predisposing factors

General

  • Gray.
  • Increasing age.

Pathophysiology

  • Generally slow-growing, darkly pigmented neoplasms, caused by abnormal melanoblastic proliferation. These tumors do not usually metastasize.
  • A disturbance in melanin metabolism may be associated with graying and act to stimulate melanoblastic proliferation → focal areas of dermal overproduction.
  • Both eyelid and intra-ocular melanomas are slow-growing, locally expansive, pigmented tumors that do not metastasize.
  • Intra-ocular melanomas are usually derived from the anterior uvea, eg the iris or ciliary body.

Timecourse

  • Slow-growing (months to years).

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Brooks D E (2007) Corpora nigra/iris cysts in the horse. Equine Vet Educ 19 (10), 512-514 Wiley.
  • Henson F M D & Dobson J M (2004) Use of radiation therapy in the treatment of equine neoplasia. Equine Vet Educ 16 (6), 315-318 Wiley.
  • Fleury C et al (2000) The study of cutaneous melanomas in Camargue-type gray-skinned horses (2) - epidemiological survey. Pigment Cell Res 13 (1), 47-51 PubMed.
  • Lavach J D & Severin G A (1977) Neoplasia of the equine eye, adnexa and orbit, a review of 68 cases. JAVMA 170 (2), 202-203 PubMed.

Other sources of information

  • Knottenbelt D C, Patterson-Kane J C & Snalune K L (2015) Clinical Equine Oncology. Elsevier, London.


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