Equine papillomavirus type 2‐associated, carcinomatous lesions of the penis and laryngopharynx of an elderly Icelandic horse gelding

Abstract

A 28‐year‐old Icelandic horse gelding was presented with a laryngopharyngeal squamous cell carcinoma. The gelding had been treated for penile carcinoma in situ with a partial phallectomy 2 years earlier. Polymerase chain reaction of tumour DNA and subsequent amplicon sequencing revealed that the equine papillomavirus type 2 E6 oncogene sequences of both lesions were identical. There is strong evidence that equine papillomavirus type 2 is causally associated with genital squamous cell carcinomas and precancerous lesions. Recent reports indicate that equine papillomavirus type 2 might also play an active role in the pathogenesis of approximately 20% of equine squamous cell carcinomas in the oronasal, pharyngeal and laryngeal regions. To the authors’ knowledge, this is the first report of a horse consecutively developing a penile carcinoma in situ and a laryngopharyngeal squamous cell carcinoma that were apparently induced by the same equine papillomavirus type 2 variant. Possible equine papillomavirus type 2 infection pathways in this horse and the importance of early detection of lesions are discussed in this context.

Equus caballus papillomavirus type 2 (EcPV2)‐associated benign penile lesions and squamous cell carcinomas

“…SCCs are invasive tumours that compromise the health of affected horses. SCCs typically affect elderly horses, as seen in our study (Lale et al., 2023 ; Sykora & Brandt, 2017 ; Van Den Top et al., 2008 ). In our study population, the mean age of horses with SCC of any location was 20 years with most of the horses being warmbloods (38%), followed by Icelandic horses (24%), Welsh ponies (9.5%) and Shetland ponies (9.5%).…”

“…In humans, oropharyngeal SCCs are most often associated with HPV type 16 (Hibi et al., 2019 ; Zaravinos, 2014 ). In our study, no other concomitant EcPV2‐associated lesions were reported in the same horse, although there have been a few reports of horses showing two separate EcPV2‐associated lesions in different locations (Bogaert et al., 2012 ; Lale et al., 2023 ; Porcellato et al., 2020 ). However, in cases of multifocal manifestation of EcPV2‐associated carcinomatous lesions, it often remains unclear whether this is due to metastatic disease or just coincidental development of the lesions.…”

“…Additionally, we identified EcPV2 nucleic acids in a laryngeal SCC of one horse. Previously, EcPV2 DNA was detected in a guttural pouch SCC of a horse with associated laryngeal and laryngotracheal SCCs and laryngeal papillomatous lesions and in a laryngopharyngeal SCC of a horse (Hibi et al, 2019;Lale et al, 2023). Additionally EcPV2…”