Squamous Cell Carcinoma - Donkey

Introduction

Squamous cell carcinoma-like lesion. This resolved with potassium iodide therapy suggesting that it was in fact a pyogranuloma.(Image courtesy of The Donkey Sanctuary)

Squamous cell carcinoma (SCC) is one of the common neoplasms affecting the eyelids and the third eyelid. It occurs in donkeys in much the same way and character as in horses, although there may be less correlation with non-pigmented skin. It is likely that the prevalence is lower than in horses, but there is no firm published information. Cutaneous and ocular forms are, in D. Knottenbelt’s limited experience, more common than penile/vulvar forms. Ulcerative and proliferative (and mixed destructive-proliferative) forms do occur.

Signalment

In Victoria Grove’s opinion donkeys with pink skin around the eyes are more at risk. These donkeys will have to have lifelong sun protection in the form of sun block or, preferably, a mask. Sadly, it often affects young animals of an average age between eight and ten years. Geldings carry a higher risk.

Diagnosis

• Diagnosis is invariably achieved by careful biopsy of a representative site.
• SCC is aggressive locally, but slow to metastasise. If associated with the orbit or eyelids, SCC carries a poor prognosis compared to cornea or conjunctival involvement. Always check for metastasis: palpate the regional lymph nodes and bony orbit, auscultate the chest and check the rest of the body, especially the perineal and preputial areas. About 15% are bilateral
• Check any skin lesion around the eyelid margins that is ulcerative. Repulse the eyeball to study the third eyelid. Prompt action should be taken to investigate. Biopsy is essential for diagnosis.
• Other neoplasms have been reported.

Treatment

Treatment and prognosis depend on the tumour type, site and extent.

Treatment options are effectively limited to surgical excision or cryosurgery. There are no scientific comparative studies on the use of cisplatin, 5-fluorouracil or radiation in donkeys and, given the paucity of literature reports, it is difficult to predict which treatments are best in any particular circumstances. Typically for all neoplastic diseases the best prognosis is likely to be achieved with aggressive treatment of small lesions.

Prognosis should be considered before embarking on therapy. Orbital involvement carries a poor prognosis.

• Extensive tumours may require enucleation
• Surgical excision of the tumour carries a 55% recurrence rate in horses
• Treatment may require referral and hospitalisation, as effective treatments may involve radiotherapy, cryotherapy or immunotherapy. Costs may be considerable. Specialist advice should be sought

Prevention

It is difficult to give any advice regarding prevention, but sunlight is a potential carcinogen for nonpigmented skin. Exposure to sun of the ear tips and non-pigmented eyelids or nictitans mucosa may be significant factors.

References

• Grove, V. (2008) Conditions of the eye In Svendsen, E.D., Duncan, J. and Hadrill, D. (2008) The Professional Handbook of the Donkey, 4th edition, Whittet Books, Chapter 11
• Knottenbelt, D. (2008) Skin disorders In Svendsen, E.D., Duncan, J. and Hadrill, D. (2008) The Professional Handbook of the Donkey, 4th edition, Whittet Books, Chapter 8

NEOPLASTIC SKIN DISORDERS - DONKEY EYELID DISEASES - DONKEY

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