Progression of aural plaques to squamous cell carcinoma in a horse

Abstract

Background Aural plaques are associated with and thought to be caused by one or more Equus caballus papillomaviruses (EcPV). Aural plaques have not previously been reported to be associated with squamous cell carcinoma (SCC). Hypothesis/Objectives To describe a horse with aural plaques and squamous cell carcinoma (SCC) on the right pinna. Animals A 28‐year‐old thoroughbred gelding presented for multiple plaques and a mass on the right pinna. Methods and materials Pinnal resection, histopathological investigation, multiple conventional PCRs for papillomavirus DNA and Sanger sequencing were performed. Results Multiple, raised, pale tan, fronded plaques covered 60% of the concave surface of the right pinna. Focally these plaques coalesced into an exophytic ulcerated mass near the base of the pinna. Multiple aural plaques and a SCC were diagnosed histopathologically. EcPV4 was detected via PCR in a sample of the SCC. Conclusions and clinical importance This report demonstrates the possibility of malignant transformation from aural plaques to SCC on the pinna of a horse. To the best of the authors' knowledge, this is the first report of EcPV4 associated with SCC.

Multi‐modality imaging of aggressive submural neoplasia of the hoof in two horses

“…28 Malignant transformation is rare in equids although cases of malignant transformation of aural plaques to squamous cell carcinoma and a mid-tail melanocytoma as well as a case of B-lymphocyte transformation in immune mediated keratitis has been reported in the literature. [30][31][32] In contrast to Horse 2, Horse 1 did not have a known inciting injury to the hoof wall though he had undergone multiple surgeries by the time of referral and diagnosis.…”

“…Mediators of inflammation can entice DNA damage in tumour suppressor genes and post translational modifications of proteins involved in essential cellular processes increase the risk of neoplasia secondary to the initial trauma or surgical insult to a region 28 . Malignant transformation is rare in equids although cases of malignant transformation of aural plaques to squamous cell carcinoma and a mid‐tail melanocytoma as well as a case of B‐lymphocyte transformation in immune mediated keratitis has been reported in the literature 30–32 . In contrast to Horse 2, Horse 1 did not have a known inciting injury to the hoof wall though he had undergone multiple surgeries by the time of referral and diagnosis.…”

Papillomaviruses in equids: A decade of discovery and more to come?

“…Additionally, an aural SCC containing EcPV4 DNA was reported in an aged horse with multiple aural plaques (Peters‐Kennedy et al . 2020) and a horse with EcPV8‐containing lesions was reported to have multiple SCCs as well as extensive papillomas in the inguinal region (Peters‐Kennedy et al . 2019).…”