Laryngeal squamous cell carcinoma and papilloma associated with Equus caballus papillomavirus 2 in a horse.

The study discusses a case of laryngeal squamous cell carcinoma and papilloma in a horse, linked to the Equus caballus papillomavirus 2 virus.

Research Context

• The study was focused on a unique case of a 19-year-old Thoroughbred stallion which was found to be suffering from laryngeal squamous cell carcinoma (SCC) and squamous papilloma. Notably, this condition caused the horse to experience severe wheezing due to the development of laryngopharyngeal stenosis — a narrowing of the airways.

Evidence and Findings

• Upon close examination of the tumor masses in the horse’s larynx, laryngotracheal section, and guttural pouch, researchers discovered areas affected by SCC. Furthermore, SCC cells were also found to be present in the epithelium adjacent to the papillomatous epithelium, suggesting continuity between the two.
• In the epiglottic lesion, the native cells were replaced by papilloma cells. Many of these cells had nuclear inclusion bodies that expressed the oncoprotein E6 – a characteristic observed in high risk human papillomavirus cases, suggesting similarities between human and equine papillomaviruses.
• Importantly, Equus caballus papillomavirus 2 (EcPV2) DNA was detected in the guttural pouch tumor, providing a clear link between the observed malignancies and this specific strain of papillomavirus in horses.

Conclusion

• The findings of this study suggest that laryngeal SCC and papilloma in horses can stem from infection with EcPV2 and could represent a spectrum of neoplastic lesions induced by this virus. This research provides a foundation for further studies on the pathogenesis of EcPV2 and its associated malignancies in horses, which may also aid in our understanding of high-risk human papillomaviruses.