What is equine cancer?

Oncology is a word used to describe the study and treatment of tumours, or neoplasms. Cancer refers to tumours which invade local tissues and spread to other part of the body (metastasise). Tumours are generally characterised as benign (non-cancerous and do not spread to other regions of the body) or malignant (cancerous- spread around the body, are invasive to local tissues and grow uncontrollably). In each individual case, this classification is usually based on histological features (tissue structures seen under a microscope) and pre-existing knowledge about the type and location of the tumour.

How common are tumours in horses?

Cancer is a disease that people tend to think of as only affecting humans however it also occurs in animals. Generally, the longer we live the more likely we are to develop cancer, and this applies to horses too. Advancements in equine medicine and the ever increasing status of horses as pets rather than working animals means that they are living longer, and so we are seeing more and more tumours, both benign and malignant.

Despite this, cancer is still less common in horses than in humans and other animals. Research into equine cancer is sparse, and diagnosis techniques are relatively rudimentary. The horse’s large body size makes cancer difficult to detect and so, it is impossible to know the true incidence of cancer in our equine populations.

Over 80% of tumours diagnosed in horses affect the skin. Whether this is because the skin can be seen, and so tumours are easy to diagnose, or it truly represents the distribution of tumours we don’t know. Techniques for diagnosis and treatment of skin tumours in horses are far more advanced than for tumours affecting other parts of the body.