Precancerous lesions and squamous cell carcinomas on the penis
Keywords: precancerous, squamous cell carcinoma, penis, stallion, equine, neoplasia
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Squamous cell carcinomas (SCC) are common neoplasms on the penises of older horses. They do not respond well to most forms of treatment and tend to recur. Their etiology is unsure. In most animals there is a general acceptance that ultraviolet light is important in the pathogenesis of SCC but for obvious reasons, that is unlikely in in these cases. In both humans and animals, has been speculated that chronic irritation caused by accumulations of smegma in the prepuce may induce tumor formation. However current data suggests a more tangible role for papilloma virus (EcPV2).
In both cases pictured above the lesions were characterized histologically as precancerous that could, in time, develop into squamous cell carcinomas. The penis at lower right was that of an aged gelding. The gelding was treated using cryotherapy. The penis at upper left was that of an intact miniature stallion, photographed in 2007. The miniature pony was not treated.
Seven years later, in 2014, the miniature stallion was presented again. At this time, the precancerous lesion had indeed become cancerous. Several foci of SCC can be seen on the glans penis.
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The large cancerous and erosive lesion seen at right, communicated with the original focus of the SCC shown at left. The stallion was euthanized.
References:
Bogaert, L. et al. 2012. EcPV2 DNA in equine genital squamous cell carcinomas and normal genital mucosa. Vet. Microbiology. 158: 33-41
Knight, C.G. et al. 2011. Equine penile squamous cell carcinomas are associated with the presence of equine Papillomavirus Type 2 DNA sequences. Vet. Path. 48: 1190-1194
Lange, C.E. 2013. EcPV2 DNA in equine papillomas and in situ and invasive squamous cell carcinomas supports papillomavirus etiology. Vet. Path. 50: 686-692
Van den Top, J.G.G. et al. 2011. Penile and preputial squamous cell carcinoma in the horse and proposal of a classification system. Equine Vet. Ed. 23: 636-648
