Expression of p53, Ki67, EcPV2- and EcPV3 DNA, and viral genes in relation to metastasis and outcome in equine penile and preputial squamous cell carcinoma.
Authors: van den Top J G B, Harkema L, Lange C, Ensink J M, van de Lest C H A, Barneveld A, van Weeren P R, Gröne A, Martens A
Journal: Equine veterinary journal
Summary
Equine penile and preputial squamous cell carcinoma (SCC) carries significant mortality risk, yet prognostic indicators remain poorly understood. Van den Top and colleagues examined 103 tumour samples from 87 horses with varying degrees of neoplastic disease, grading them histologically and analysing p53 and Ki67 protein expression alongside detection of equine papillomavirus (EcPV) types 2 and 3 using both conventional and quantitative PCR methods. Poorly differentiated tumours demonstrated markedly worse outcomes, with mortality rates escalating from 8.3% in papillomas to 63.3% in grade 3 (G3) carcinomas, and these less differentiated subtypes also showed stronger correlation with p53 expression and metastatic disease (r = 0.769, P = 0.001). Although EcPV2 DNA was detected in 89.4% of cases, neither the presence nor quantitative expression of viral oncogenes (E2, E6, L1) nor Ki67 expression predicted survival or metastatic potential. Histological tumour grading emerges as the single most valuable prognostic tool for equine practitioners, enabling evidence-based counselling on survival likelihood and informing treatment decisions, whilst viral status and proliferation markers appear less clinically actionable in this context.
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Practical Takeaways
- •Histological grading of penile/preputial tumours is essential for prognosis and treatment planning; poorly differentiated tumours have 63% mortality risk vs 8-26% for better-differentiated lesions
- •Presence of EcPV2 is common in these tumours but does not independently predict outcome, so viral testing should not replace histopathological assessment
- •Horses with grade 3 tumours require more aggressive treatment and careful monitoring for metastases; lower-grade tumours have substantially better survival prospects
Key Findings
- •EcPV2 DNA detected in 89.4% and EcPV3 in 1.5% of horses with penile/preputial tumours
- •Tumour differentiation grade strongly correlated with metastasis occurrence (r=0.769, P=0.001) and p53 expression (r=0.429, P<0.001)
- •Survival rates differed significantly by tumour grade: papilloma 8.3%, G1 26.1%, G2 26.3%, G3 63.3% mortality
- •p53, Ki67 expression and EcPV presence/expression were not independent prognostic factors; tumour grading alone is the key predictor