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Ocular squamous cell carcinoma
Synonym(s): eye cancer SCC neoplasia
Introduction
- Incidence: most common bovine tumor in any location – according to estimates from inspected abattoirs in the USA, 12.5% of bovine carcass condemnations were due to ocular squamous cell carcinomas.
- Signs: locally invasive, slow growing, very rare metastases to local lymph nodes, the bony orbit, sinuses, brain or thorax; mainly affects eyelids, lacrimal caruncle, third eyelid, conjunctiva or cornea.
- Treatment: depends upon the location and extent of tumor, wide surgical excision generally the treatment of choice
- Prevention: useful in predisposed individuals or geographical areas.
- Prognosis: overall relatively good depending upon the speed of detection, extent and anatomic position of the lesion(s).
Presenting signs
- Variable history depending on extent and anatomic position of the lesion.
- Lesion may vary from erosive/ulcerative → hyperplastic papilloma-like masses → granulomatous, necrotic and ulcerative.
- Premalignant lesions are white, small, elevated, hyperplastic plaques, whereas malignant lesions are more irregular, nodular, pink, erosive and necrotic. Squamous cell carcinomas that invade the orbit can aggressively invade bone.
- The most common location is the lateral limbus, followed by eyelid margins (especially lower eyelid), nicitating membrane, and medial canthus. The cornea may also be affected.
- Clinical signs from metastatic lesions are uncommon, although lymphatic invasion may occur.
Geographic incidence
- High UV light areas, eg those at high altitude or latitudes nearer the equator.
- Exposure to increased levels of actinic radiation increases the prevalence of the disease.
Age predisposition
- Peak age at incidence is 8 years old.
Breed/Species predisposition
- Herefords Hereford appear to be predisposed, most likely because of the strong genetic trait for a white face; incidence varies from 0.8-5% among herds
- Simmentals Simmental and Holstein-Friesians Holstein Friesian are occasionally affected; rarely seen in other breeds
- More frequent in Bos taurus Bos taurus.
Cost considerations
- Treatment may involve surgical intervention of varying degrees.
- Recurrence → additional expense.
- Carcass condemnation at slaughter.
Special risks
- Ocular lesions may metastasize to regional lymph nodes, salivary glands or thoracic cavity - rare.
Pathogenesis
Etiology
- Unknown.
- Heritability, sunlight, nutrition, eyelid pigmentation and possibly a viral cause are all implicated.
- Appears to be associated with a high plane of nutrition.
- In periocular/ocular region postulated causes include:
- Prolonged or increased exposure to UV light → chronic irritation and inflammation.
- Light or non-pigmented tissue.
- Mucocutaneous junctions are predisposed to metaplastic histological changes.
- Possible viral etiology – infectious bovine rhinotracheitis and papilloma virus have been isolated from the lesions, but the significance is uncertain.
Predisposing factors
General
- White face.
Specific
- High UV light intensity, eg at high altitude or tropical/subtropical areas.
- Aging: chronic exposure.
- Pink or lightly pigmented eyelids and periocular tissues.
Pathophysiology
- Locally invasive malignant tumor of mucocutaneous junctions.
- Slow to metastasize.
- Three main forms:
- Proliferative.
- Ulcerative/destructive.
- Mixed.
- Locally invasive, usually slowly growing lesion(s) in areas of non-pigmented skin or mucosa.
- Advanced cases may occur with invasion of the orbit, ocular tissues, paranasal sinuses or brain.
- Very rarely metastasize to regional lymph nodes, salivary glands or beyond - often slow to occur.
- Carcinoma in situ (corneal form) is rarest.
Timecourse
- Variable.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed Papers
- Recent references from PubMed and VetMedResource.
Other sources of information
- Roberts S M (2009) Ocular neoplasia. In: Large animal internal medicine. Eds: Smith P. Mosby Elsevier, USA. pp 1299-1305.