Solitary pedunculated multicystic viral plaque associated with canine papillomavirus 18 in a British Bulldog.

A pedunculated exophytic mass developed on the rump of a dog. Fine-needle aspiration revealed keratin debris suggestive of a follicular tumor. However, histology revealed a pigmented viral plaque that contained numerous keratin-filled cystic cavities. Canine papillomavirus 18 DNA sequences were detected in the lesion. Viral plaques are typically multiple sessile lesions of dogs. A viral plaque appearing as a solitary exophytic keratin-filled mass has not been reported previously, to our knowledge. The novel clinical findings in this case expand the ways that viral plaques may appear in dogs. In addition, the histologic findings represent a novel pathologic entity of dogs. Given that canine viral plaques can be progressive, and dogs typically develop numerous plaques, it is important to differentiate between a viral plaque and a hair follicle tumor.

Evidence from a Series of 104 Equine Sarcoids Suggests That Most Sarcoids in New Zealand Are Caused by Bovine Papillomavirus Type 2, although Both BPV1 and BPV2 DNA Are Detectable in around 10% of Sarcoids.

Equine sarcoids are common mesenchymal neoplasms of horses that are caused by cross-species infection by deltapapillomaviruses. While bovine papillomavirus (BPV) 1 and 2 are the most common causes, there are differences between countries regarding which of these BPV types cause the majority of sarcoids. Additionally, no causative PV can be detected in a subset of sarcoids, suggesting that other PV types could be rarer causes of these neoplasms. In the present study, consensus PCR primers and PCR primers specific for the five deltapapillomavirus types currently known to cause mesenchymal neoplasia (BPV1, BPV2, BPV13, BPV14, and Ovis aries PV2 DNA) were used to investigate the presence of PV DNA in 104 sarcoids from three defined regions in New Zealand and from two distinct time periods separated by 15 years. PV DNA was detected in 94 (90.4%) sarcoids. Of the sarcoids containing PV DNA, 83 (88.3%) contained only BPV2 DNA, 9 (9.6%) BPV1 and BPV2 DNA, and 2 (2.1%) only BPV1 DNA. No other PV types were detected. The predominance of BPV2 is consistent with studies of sarcoids from North America but dissimilar to studies of sarcoids from Europe and Australia. Detection rates of BPV1 and BPV2 were similar in sarcoids from different regions of New Zealand and in sarcoids from different time periods. These results suggest that most equine sarcoids in New Zealand are caused by BPV2 and thus if vaccines are developed to prevent sarcoids, vaccines that provide good protection against BPV2 will be required in this country.

Detection of Ovis aries papillomavirus type 2 DNA sequences in a sarcoid-like mass in the mouth of a pig.

An oral mass was surgically excised from the gingiva of a pig. As the mass had a similar histological appearance to an equine sarcoid, DNA was extracted and consensus PCR primers used to amplify papillomavirus (PV) DNA. DNA sequences from Ovis aries papillomavirus (OaPV) type 2 were amplified both from a section of the entire mass as well as an area deeper within the mass away from the surface of the lesion. No other PV types were detected within the oral lesion. Ovis aries PV2 is a Delta PV that is closely related to the bovine Delta PVs that cause sarcoids in horses and cats. These results suggest that OaPV2 may be able to infect pigs and this virus could have caused the mesenchymal neoplasm in the mouth of this pig. This is the first evidence that a non-bovine PV can infect a non-host species and the first report of a sarcoid-like mass in pigs. These observations add to the range of species in which PV-associated neoplasia has been reported and suggest that cross-species infection by other Delta PV types may be possible.

Identification of Felis catus papillomavirus 3 in skin neoplasms from four cats.

Bowenoid in situ carcinomas (BISCs) are papillomavirus (PV)-induced skin neoplasms that are thought to be caused by Felis catus papillomavirus (FcaPV) 2. As BISCs are typically multiple and can become extensive, they can be difficult to treat. Herein we describe 4 cats that developed skin neoplasms that contained FcaPV-3 DNA. One cat developed multiple basal cell carcinomas (BCCs), 1 a BISC with unusual extension into hair follicles, and 2 developed a single typical-appearing BISC. All neoplasms contained prominent PV-induced cell changes and intense p16CDKN2a protein immunostaining. Results from these 4 cats provide evidence that FcaPV-3 could cause a proportion of feline skin cancers, albeit less frequently than FcaPV-2. Excision of the typical BISCs and the BCCs appeared curative. Although the cat with the unusual BISC was euthanized because of the large size of the lesion, evidence from these 4 cats suggests that skin neoplasms that contain FcaPV-3 DNA may have a less aggressive clinical behavior than those associated with FcaPV-2. A consistent feature of the neoplasms in all 4 cats was the presence of prominent basophilic intracytoplasmic inclusion bodies; these inclusions have not been reported in lesions caused by FcaPV-2, to our knowledge, and their detection may allow differentiation between the different PV types and could therefore be a useful prognostic feature.

The detection of Felis catus papillomavirus 3 DNA in a feline bowenoid in situ carcinoma with novel histologic features and benign clinical behavior.

Bowenoid in situ carcinoma (BISC; papillomavirus-associated squamous cell carcinoma in situ) is an uncommon skin neoplasm of cats that can result in euthanasia because of the development of multiple lesions or because of progression to invasive squamous cell carcinoma. BISCs are currently thought to be caused by Felis catus papillomavirus 2 (FcaPV-2). The presently described cat developed a single 0.5 cm in diameter interscapular mass. Over the following 18 months, the mass doubled in size; no additional lesions developed. The mass was surgically excised and histologically diagnosed as a BISC. However, in contrast to previously reported BISCs, neither prominent thickening of the deep aspects of the follicular infundibula nor marked cell dysplasia were present. Furthermore, ~50% of the keratinocytes in the affected epidermis had prominent PV cytopathic changes that included shrunken angular nuclei and elongated basophilic cytoplasmic inclusions. As the histopathology was not typical for FcaPV-2 infection, polymerase chain reaction was performed and revealed only DNA sequences from Felis catus papillomavirus 3 (FcaPV-3). No further BISCs developed in this cat 6 months postremoval, hence surgical excision appeared to be curative. Results from this case suggest that, although FcaPV-2 appears to be the predominant cause of BISCs in cats, infection by FcaPV-3 can also cause these neoplasms. BISCs caused by FcaPV-3 appear to have unique histologic features that allow the causative PV type to be predicted. Results from this single case suggest that BISCs caused by FcaPV-3 may have a more benign clinical course than those caused by FcaPV-2.