Multiple cutaneous inverted papillomas in a dog a*
E P Lane and U Tübbesing
ABSTRACT Cutaneous inverted papillomas are described in an 8-month-old mixed breed domestic dog from Windhoek, Namibia. Multiple firm, rapidly growing, doughnut-shaped masses formed on the ventral abdomen, which histologically consisted of a cup-shaped rim of marked epithelial hyperplasia, giant keratohyaline granules and prominent koilocytes and marked hyperkeratosis filling the centre of the mass. Current literature on canine papillomas is briefly reviewed. Key words: canine, inverted papilloma, papilloma virus, skin. Lane E P, Tübbesing U Multiple cutaneous inverted papillomas in a dog. Journal of the South African Veterinary Association (2007) 78(4): 221–223 (En.). Pathology Section, Department of Paraclinical Studies, Faculty of Veterinary Science, Private Bag X04, Onderstepoort 0110 South Africa.
INTRODUCTION Canine cutaneous viral squamous papillomas are caused by papilloma viruses14. Although the exophytic oral and facial form (warts and verrucae) are common in the dog14, cutaneous endophytic inverted papillomas (CIP) are less common4,7. Cutaneous inverted papillomas are usually seen in dogs under 3 years of age, occur on the ventral abdomen and groin, and are typically small (<2 cm diameter), raised and firm with a central pore7,14. This case report describes a case of multiple CIP in a mixed breed dog from Windhoek, Namibia.
the outer rim consisted of florid papillary epidermal hyperplasia with closely packed rete pegs and scant intervening dermis (Fig. 3). Epidermal cells were tightly packed, disorganised, had a high mitotic rate (5/HPF), scant eosinophilic cytoplasm and large round to oval nuclei with coarsely clumped chromatin and multiple, large magenta nucleoli. Irregular and disorganised keratinisation was characterised by prominent large keratohyaline granules and marked mainly orthokeratotic hyperkeratosis and dyskeratosis
(Fig. 4). Individual cell necrosis was common, and particularly on the edges of the papillae, associated with ballooning degeneration (koilocytes) and intra- and intercellular oedema. Rare cells swollen with basophilic granular cytoplasm were present. Intranuclear inclusions were not seen. Adjacent and overlying epidermis was attenuated. Electron microscopy revealed no viral particles. A diagnosis of canine CIP was made. DISCUSSION The clinical presentation, macroscopic and histological features of these tumours are consistent with CIP4. Intracutaneous cornifying epithelioma was ruled out on the presence of typical ballooning degeneration and the absence of a complex branching cyst wall containing keratin pearls and dermal infiltration by cusps of basal cells15. As in this case, intranuclear inclusions may be absent in CIP6. Multiple papilloma viruses are implicated in the development of canine papillomas, and the virus responsible for CIP appears to be a different virus from the one which causes oral and facial papillo-
CASE HISTORY An 8-month-old, male, mixed breed, unvaccinated domestic dog in good bodily condition was presented for veterinary attention because of multiple, rapidly growing, well-circumscribed, firm, raised, fig-shaped masses around the prepuce (Fig. 1). A basic clinical examination, restricted by cost considerations, showed no other abnormalities apart from a mild eosinophilia on blood smear, which was attributed to the mild tick burden and/or internal parasites. Fine-needle aspiration of the masses was unrewarding. Routine histological processing followed excisional biopsy of the masses. On section, the masses were firm with a pale tan outer rim and an inner lamellar section with a central raised pore (Fig. 2). Histologically, a
Pathology Section, Department of Paraclinical Studies, Faculty of Veterinary Science, Private Bag X04, Onderstepoort, 0110 South Africa.
Rhino Park Veterinary Clinic, PO Box 50533, Bachbrecht, Windhoek, Namibia. *Author for correspondence. E-mail: [email protected] Received: August 2006. Accepted: October: 2007.
Fig. 1: Macroscopic appearance of cutaneous inverted papillomas around the prepuce of a dog: firm, raised, discrete nodules with a central pore (shown to scale).
0038-2809 Jl S.Afr.vet.Ass. (2007) 78(4): 221–223
Fig. 2: Cut section of cutaneous inverted papilloma showing lamellar arrangement of keratin (arrows) and a central raised pore (arrowhead) (scale bar = 2 mm).
Fig. 3: Histological appearance typical of a papilloma papillary epidermal hyperplasia forming closely packed rete pegs (stars) with hyperkeratosis (arrow) (H&E; scale bar = 500 µm).
matosis4. In natural and experimental infections, papilloma viruses may cause a wide range of skin lesions including epidermal hyperplasia, epidermal cysts, squamous papilloma, fibropapilloma, inverted papilloma, basal cell epithelioma, and squamous cell carcinoma3,6. Human inverted papillomas are curiously most common in the nasal mucosa2. Immunohistochemical stains, using polyclonal antiserum, showed that 44.2% of 95 canine cutaneous papillomas and 27 % of 100 squamous cell carcinomas contained papilloma viral antigen; antigen was detectable in 54.2 % of all oral and ocular papillomas and in 37.0 % of all cutaneous papillomas13. Viral transmission occurs by direct or indirect contact, and infection is believed to be established in damaged skin or oral mucosa14. Most canine papillomas regress naturally following infiltration by CD4+ and CD8+ T lymphocytes 1 1 , 1 2 . Solid immunity, thought to be due to production of circulating neutralising antibodies against the viral capsid antigens5,12, usually follows experimental or natural infection11. Unusually severe or persistent forms of papilloma are associated with immune suppression, old age and recent chemotherapy or corticosteroid therapy1,8,–10,12. Treatment of papillomas may include excision, cryo- or electrosurgery, injection with autogenous vaccine, and immune modulating drugs14. Since papillomas may regress spontaneously, the efficacy of autogenous vaccines is difficult to accurately assess12. Canine cutaneous papillomas are typically benign, rarely recur after excision and often spontaneously regress in time7; but malignant transformation has been recorded14. Control of papilloma virusinduced disease in multiple-dog households is hampered by the fact that canine oral papilloma virus, and presumably, other canine papilloma viruses are fairly stable in the environment12. ACKNOWLEDGEMENTS We thank the laboratory staff of the National Health Laboratory Service, Tshwane Academic Division, and Mrs Erna van Wilpe of the Electron Microscopy Unit, Faculty of Veterinary Science, University of Pretoria, for excellent technical assistance and Professor A Leisewitz for valuable consultation. REFERENCES
Fig. 4: Histological appearance typical of a papilloma – hyperplastic epidermal cells (star) undergoing irregular keratinisation with large intracytoplasmic keratohyaline granules (arrowheads) (H&E; scale bar = 15 µm). 222
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