Equis ISSN 2398-2977

Eye: squamous cell carcinoma

Synonym(s): SCC

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

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).
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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

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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.
  • 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.


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