The Royal Veterinary College has announced that work it conducted with King’s College London (KCL), the University of Edinburgh and University College London (UCL), has led to a breakthrough in the understanding of squamous cell carcinoma (SCC)1.

Squamous cell carcinoma affects horses’ genitalia, eyes, or skin around the eyes. The tumours typically have a guarded to poor prognosis, and the therapeutic approaches available have variable success rates. Euthanasia on welfare grounds is necessary in a significant number of cases.

Before this new research was published, pathologists and researchers Dr Alejandro Suárez-Bonnet and Professor Simon Priestnall, both from the RVC, had already undertaken research which showed that equine squamous cell carcinoma affecting the penis frequently acquires the ability to degrade the extracellular matrix and become much more biologically aggressive2. This is known as ‘epithelial to mesenchymal transition’.

This new study, recently published in Scientific Reports, is the product of a multi-institutional effort, which used both “classical” anatomic histopathology assessment and artificial intelligence to demonstrate a correlation between chronic inflammation, equine papillomavirus infection and progression of equine penile squamous cell carcinoma.

Several additional cancer-related signalling molecules, which are important in researchers’ understanding of human penile cancer, were also studied and the results obtained will lead to a much better understanding and treatment of the cancer.

Simon Priestnall, Professor of Veterinary Anatomic Pathology at the Royal Veterinary College, said: “Equine squamous cell carcinoma is the second most common type of cancer in horses, with a variable prognosis, so we are delighted to have made this breakthrough that provides a greater understanding and can lead to more effective treatments for horses and their owners. 

"The RVC has always recognised the value of collaboration, and Alejandro and I enjoyed working alongside the teams at KCL, the University of Edinburgh and UCL. This project shows what can be achieved when different organisations work together with a common aim and we hope the similarities between the tumour in horses and people can offer a true One Health benefit."

Dr Alejandro Suárez-Bonnet, Lecturer in Comparative Pathology at the Royal Veterinary College, said: "I am so pleased with the results of this study, which will hopefully pave the way for improved prognosis of horses diagnosed with equine squamous cell carcinoma. 

"Our work is not over, however. Thanks to the help of a grant from the Horse Race Betting Levy, Simon and I are leading a Master’s degree project investigating equine penile, ocular and vulvar squamous cell carcinomas from a broader perspective.

"Our hope is to identify if variability exists between equine papillomavirus infectious status, morphological and microscopic difference, and cancer progression, with the aim of identifying potential therapeutic targets as well as diagnostic markers with prognostic implications for maximum benefit to the British equine population.”


  1. Arthurs C, Suarez-Bonnet A, Willis C, Xie B, Machulla N, Mair TS, Cao K, Millar M, Thrasivoulou C, Priestnall SL, Ahmed A (2020) Equine penile squamous cell carcinoma: expression of biomarker proteins and EcPV2. Scientific Reports 12; 10(1):7863. doi: 10.1038/s41598-020-64014-3.
  2. Suárez-Bonnet A, Willis C, Pittaway R, Smith K, Mair T, Priestnall SL (2018) Molecular carcinogenesis in equine penile cancer: A potential animal model for human penile cancer. Urologic Oncology. 36 (12):532.e9-532.e18 doi: 10.1016/j.urolonc.2018.09.004

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