Detection of papillomavirus in equine periocular and penile squamous cell carcinoma

Abstract

Squamous cell carcinoma (SCC) is the most common tumor arising in the periocular and penile areas of horses. Both ultraviolet radiation and papillomaviruses have been implicated in the pathogenesis of SCC in various species, including the horse. This retrospective study used polymerase chain reaction (PCR) to detect papillomavirus DNA in archival biopsy samples from equine periocular and penile SCC from 3 different geographic areas (northeast, southeast, and central United States). Forty-two periocular SCCs were tested; none contained papillomavirus DNA. Twenty-two penile SCCs were tested, and papillomavirus DNA was identified in 10 (43%) cases. Sequencing of the PCR products revealed homology with Equus caballus papillomavirus 2 (EcPV-2). No geographic distribution in the detection of papillomavirus was identified. Penile SCCs were significantly more likely to be papillomavirus positive than the periocular SCCs ( P < 0.001). The role of papillomavirus in the development of penile SCC requires further investigation. The differing pathogeneses of periocular and penile SCC suggest that the tumors may respond differently to treatment.

A Penile Squamous Cell Carcinoma With Systemic Metastasis in a Thoroughbred Horse

“…However, UV overexposure is a less likely cause for equine PSCC due to the ventral location of the male genitalia. 2,4 The carcinogenic e®ect of smegma has been proposed, but the scienti¯c evidence in support of it is relatively sparse and controversial. [12][13][14][15] In humans, approximately 40% of PSCC cases are associated with PV infection, but its prevalence varies among di®erent PSCC subtypes, ranging from 0% to 100%.…”

“…5 However, while some researchers have detected EcPV2 DNA in almost 100% of the cases of equine penile papillomas and PSCC examined, 1,3,9,17 others have found them in only 40% of such cases. 4,18 These¯ndings suggest a possibility of di®erent pathogeneses in the development of equine penile papilloma and PSCC, wherein EcPV2 may serve as the initiator, but subsequent tumor promotion and progression to malignancy can vary and are not necessarily associated with EcPV2. 4,19 It is also likely that EcPV2 may be eliminated by the host responses before the development of cancerous lesions and thus be undetected intralesionally.…”

“…[1][2][3][4][5] The prognosis of equine PSCC is generally poor because their common recurrence after treatment and metastasis to regional lymph nodes and/or internal organs. 6 Distant metastasis of PSCC is rare occurring most often in the lungs and liver, 6 and the peritoneal metastasis (peritoneal carcinomatosis) of PSCC is extremely rare.…”

Investigation of a Putative Novel Papillomavirus that causes InvertedPapillomas in Horses

“…Papillomas are common equine neoplasms that affect several cutaneous sites, as well as oral, ocular and genital mucous membranes [1][2][3][4][5][6]. To date, almost 200 distinct papilloma viruses have been cloned, sequenced, and allocated to various genera, including seven viruses termed EcPV1-7 that were identified in equine papillomas [7][8][9].…”

“…EcPV2 has been identified from equine papillomas affecting the genital area and may involve in the development of penile squamous cell carcinomas [9,13,14]. EcPV4 was found in genital plaques, EcPV2, EcPV3, EcPV4, EcPV5 and EcPV6 in aural plaques, and EcPV7 in penile masses [3,6,9]. EcPV2 has a distinct restriction endonuclease digestion pattern and showed only moderate cross-hybridization with EcPV1 on low stringency Southern blot hybridization [7,8].…”