equis - Articles
Eye: squamous cell carcinoma
Synonym(s): SCC
Introduction
- Incidence: most common ocular tissue neoplasia with increasing incidence with age, decreased skin pigmentation, light colored coats and increased exposure to UV light.
- 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.
- 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.
- The third eyelid and conjunctiva are the most commonly affected areas.
- Occasional lesions at limbus (temporally) and upper and lower eyelids.
- Characteristic mucopurulent discharge in most cases.
- Early (pre-carcinomatous) cases have detectable blood in lacrimal secretions.
- Corneal lesions may be subtle in early stages; corneal opacity with prominent neovascularization, with or without concurrent granulation tissue-like proliferation.
Geographic incidence
- High UV light areas, eg those at high altitude or latitudes nearer the equator.
Age predisposition
- Most commonly diagnosed at 7-10 years of age.
- Occasionally seen in younger or older horses.
Breed/Species predisposition
- Clydesdale Clydesdale.
- Shire Shire.
- Pinto Pinto.
- Appaloosa Appaloosa.
- Weakly-colored horses, eg palominos Palomino and creams.
- Horses with pink or lightly pigmented eyelids and periocular tissues.
- Horses with primary periorbital/palpebral vitiligo.
Cost considerations
- Treatment may involve surgical intervention of varying degrees +/- radiation therapy.
- Recurrence → additional expense.
- Loss of use of horse.
Special risks
- Ocular lesions may metastasize to regional lymph nodes, salivary glands or thoracic cavity - rare.
Pathogenesis
Etiology
- Unknown.
- In equine 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.
- No viral etiology has been implicated.
Predisposing factors
General
- Weakly-colored horses, eg palominos Palomino and creams.
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.
- One survey recorded 28% third eyelid and/or nasal canthal lesions, 28% limbal lesions and 23% involving the lower/upper eyelid. In the UK third eyelid and/or nasal canthal lesions are probably most common.
- Carcinoma in situ (corneal form) is rarest.
Timecourse
- Variable.
Diagnosis
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Treatment
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Prevention
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Outcomes
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Pucket J D & Gilmour M A (2014) Intralesional 5-fluorouracil (5-FU) for the treatment of eyelid squamous cell carcioma in 5 horses. Equine Vet Educ 26 (6), 331-335 VetMedResource.
- Taylor S & Haldorson G (2013) A review of equine mucocutaneous squamous cell carcinoma. Equine Vet Educ 25 (7), 374-378 VetMedResource.
- Elce Y A, Wilkie D A, Santschi E M & Green E (2011) Metastasis or delayed local extension of ocular squamous cell carcinoma in four horses. Equine Vet Educ 23 (10), 496-499 VetMedResource.
- Gilger B C (2011) Challenges in the treatment of equine periocular squamous cell carcinoma. Equine Vet Educ 23 (10), 500-501 VetMedResource.
- Malalana F et al (2010) Mitomycin C, with or without surgery, for the treatment of ocular squamous cell carcinoma in horses. Vet Rec 167 (10), 373-376 PubMed.
- Mosunic C B et al (2004) Effects of treatment with and without adjuvant radiation therapy on recurrence of ocular and adnexal squamous cell carcinoma in horses: 157 cases (1985-2002). JAVMA 225 (11), 1733-1738 PubMed.
- Dugan S J, Curtis C R, Roberts S M & Severin G A (1991) Epidemiologic study of ocular/adnexal squamous cell carcinoma in horses. JAVMA 198 (2), 251-256 PubMed.
- Rebhun W C (1990) Treatment of advanced squamous cell carcinomas involving the equine cornea.Vet Surg 19 (4), 297-302 PubMed.
- Schwink K (1987) Factors influencing morbidity and outcome of equine ocular squamous cell carcinoma. Equine Vet J 19 (3), 198-200 PubMed.
Other sources of information
- Knottenbelt D C, Patterson-Kane J C & Snalune K L (2015) Clinical Equine Oncology. Elsevier Press.
- Gilger B C & Stoppini R (2005) Diseases of the Eyelids, Conjunctiva and Nasolacrimal System. In: Equine Ophthalmology. Elsevier Saunders. St. Louis. pp 107-156.