Oral Papillomas Associated With Felis catus Papillomavirus Type 1 in 2 Domestic Cats

Abstract

Multiple small sessile raised lesions were detected on the ventral surface of the tongue in two 13-year-old domestic cats. The lesions were incidental in both cats. Lesions from both cats appeared histologically as well-demarcated foci of markedly thickened folded epithelium that formed keratin-filled shallow cuplike structures. Large keratinocytes that contained a swollen nucleus surrounded by a clear cytoplasmic halo (koilocytes) were common, suggesting a diagnosis of a papillomavirus-induced papillomas, and papillomavirus antigen was demonstrated by immunohistochemistry. The papillomas exhibited diffuse intense cytoplasmic and nuclear immunoreactivity against cyclin-dependent kinase inhibitor 2A protein (also known as p16 or INK4a protein). Felis catus papillomavirus type 1 DNA sequences were amplified from both papillomas. The papillomas resolved in 1 cat within 3 months of diagnosis, while the papillomas were still visible 4 months after diagnosis in the other cat. This is the first evidence that these papillomas are caused by F. catus papillomavirus type 1.Keywords felis catus papillomavirus, papilloma, oral cavity, wart, cat Papillomaviruses (PVs) have been detected in all species that have been studied, with most species infected by multiple PV types. Most PV infections do not result in the development of clinically detectable lesions; however, depending on both PV type and host factors, PVs can cause a range of hyperplastic and neoplastic lesions.1 Currently, 4 PV types have been fully classified from domestic cats, including Felis catus PV-1 (FcaPV-1) from a cutaneous viral plaque, FcaPV-2 and FcaPV-3 from cutaneous bowenoid in situ carcinomas, and FcaPV-4 from a sample of gingivitis.2,10 PV infection is also thought to cause feline sarcoids (fibropapillomas), although current evidence suggests that these lesions are caused by a bovine PV. The PVs of domestic cats have been referred to as Felis domesticus PVs.In contrast to those of other species, PV-induced papillomas (warts) in domestic cats are rare, with only 2 oral papillomas and 2 cutaneous papillomas previously reported.2,9 While a cutaneous papilloma was found to contain DNA sequences from a human PV type, the PV type present in oral papillomas in domestic cats has not been previously investigated. Herein, 2 cats with oral papillomas are described. Papillomas in both cats developed on the ventral surface of the tongue and contained FcaPV-1 PV DNA sequences.Cat No. 1 was a 13-year-old neutered male domestic shorthair cat that was observed during a routine dental procedure to have numerous <3-mm diameter pale raised lesions on the ventral surface of the tongue (Fig. 1). Similar lesions on the ventral surface of the tongue were also observed in a 13-year-old male neutered Abyssinian cat (cat No. 2) during surgical drainage of a ranula. Samples were taken from both cats and submitted for histology.Lesions from both cats consisted of well-demarcated foci of markedly thickened folded epithelium that projected as thick tongues into the underly...

Felis catus papillomavirus types 1 and 4 are rarely present in neoplastic and inflammatory oral lesions of cats

“…Therefore, if feline OSCCs are caused by a PV infection, FcaPV-1 and FcaPV-4 appear to be the most likely etiological agents. Recently it was found that FcaPV-1 is not amplified by the consensus PCR primers used in the three earlier studies (Munday et al, 2015). Therefore, it was hypothesized that the feline oral PVs could be a significant cause of feline OSCCs without having been previously detected.…”

“…Currently four different Felis catus PV (FcaPV) types are recognized to infect domestic cats. Of these, only FcaPV-1 and FcaPV-4 have been detected in the mouth (Dunowska et al, 2014;Munday et al, 2015). Therefore, if feline OSCCs are caused by a PV infection, FcaPV-1 and FcaPV-4 appear to be the most likely etiological agents.…”

“…FcaPV-1 was recently reported to cause oral papillomas in domestic cats (Munday et al, 2015). As this PV infects oral epithelium and subsequently stimulates cell proliferation, it was hypothesized that FcaPV-1 could influence the development of feline OSCCs.…”

Equine ocular squamous cell carcinoma: a case report

“…Abnormal RB expression results in an accumulation of p16CD-KN2A protein (p16), which can be detected using immunohistochemistry. While the presence of p16 has not previously been investigated in horse SCC lesions, recent studies of skin and oral samples revealed that p16 immunoreactivity is rarely present within feline-negative PV SCCs (Munday et al 2011b), while there was an intense cytoplasmic and nuclear immunoreactivity in oral Papillomas associated with Felis catus Papillomavirus Type 1 (Munday et al 2015).…”

“…The negative stain for p16 may be due to the lack of specificity of the monoclonal antibody used (anti-human) against the horse p16 but previously similar antibodies were shown to be useful in cats, where the specificity of monoclonal anti-human p16 antibodies for feline p16 has been documented (Munday et al 2015). Unfortunately, all these considerations are speculative because Papillomaviral doi: 10.17221/8386-VETMED DNA PCR assays were not performed.…”