If you’ve found a lump on your horse during grooming, it can raise immediate questions and concerns about cancer: You may be thinking, is it harmless or something more serious? Does my horse have cancer?
Many horse owners come across bumps or unusual growths at some point, and while not all are dangerous, some do require greater attention so they don’t impact your horse’s comfort, performance, and long-term health.
The good news is that with a bit of knowledge and early action, many equine tumors can be managed effectively. If you suspect your horse has cancer, understanding what to look for, and the next steps to take, can make all the difference.
What are equine tumors?
Equine tumors are a relatively common health concern in horses, particularly as they age. If your horse has a tumor, it can look like an abnormal mass of tissue that develops on the skin, in soft tissue, or internally.
While some tumor growths are benign (non-cancerous) and slow-growing, others can be aggressive or even life-threatening if left untreated.
The most frequently diagnosed tumors in horses include:
- Sarcoids – The most common equine tumor, often appearing as wart-like, nodular, or ulcerated lesions and are commonly found on the head, neck, chest, and legs.
- Squamous cell carcinoma (SCC) – Frequently affects areas with less pigmentation, such as around the eyes, genitals, and mouth.
- Melanomas – Found especially in grey horses, they develop under the tail, around the anus, or near the parotid gland. While many are slow-growing initially, some can become cancerous over time.
These tumors are widely different in behavior… some remain small and stable for years, while others can grow more aggressively, ulcerate, or interfere with movement and quality of life.
Signs something might be wrong
While not every lump is a tumor, it’s always worth paying attention to. At the end of the day, you know your horse the best, and small changes can be the first clue.
Keep an eye out for:
- New lumps or bumps on the skin or under the tail
- Growths that change in size or appearance
- Sores or open wounds that don’t heal
- Bleeding, discharge, or irritation from a growth
- Sensitivity when grooming or tacking up
- Behavioral changes due to discomfort
- Difficulty eating or performing
If something looks or feels different, it’s a good idea to have your veterinarian take a look sooner rather than later. If they are concerned about a growth, they’ll usually start with a close physical exam and a biopsy (taking a small sample to identify the tumor type).
Treatment options (there are more than you might think)
Treating a tumor on your horse really depends on the type of tumor, where it’s located, and how early it’s found.
Some common approaches include:
- Surgical removal – Often the first choice if the tumor is small and accessible.
- Cryotherapy or laser therapy – These methods target and destroy tumor tissue and are commonly used for sarcoids.
- Topical or immune-based treatments – Used in certain cases, particularly for skin tumors.
- Radiation therapy – Effective, but sometimes limited by cost or access.
As horses are large animals, treatment options for equine tumors are fewer than treating tumors in dogs and cats, due to accessibility.
A more targeted approach: IsoPet® therapy
For tumors in horses that are difficult to remove, or that come back after treatment, there are newer, more targeted options available.
IsoPet® therapy works by injecting a small amount of radiation directly into the tumor through a regular needle, making it an accessible option for large animals. This allows for a high dose of radiation where it’s needed most, while helping protect the surrounding healthy tissue. For horses, this can be especially helpful in sensitive areas like around the eyes or mouth, where traditional surgery can be more challenging.
IsoPet® treatment is also a great alternative to external beam radiation therapy (EBRT), which delivers focused radiation beams to shrink or destroy tumors — however, this isn’t a feasible treatment option for animals too large to fit in EBRT machines. IsoPet® delivers the same localized radiation therapy, at a higher dose, with only a single treatment.
Early detection
One of the best things you can do is to routinely observe your horse. Regular grooming isn’t just about keeping your horse looking good, it’s also your best chance to spot changes early on.
Tip: keeping a quick check-list of common problem areas (under the tail, around the eyes, along the chest and legs) can go a long way.
Focusing on your horse’s quality of life
At the end of the day, every decision comes back to your horse’s comfort and well-being.
Many tumors in horses can be managed and maintained in a way that allows your horse to stay happy, active, and pain-free. Even when a cure isn’t possible, treatments can often slow progression and improve day-to-day quality of life.
If your horse has cancer or any growths, working closely with your veterinarian will help you choose the right path based on your horse’s needs and your goals.
Final thoughts on tumors in horses
Finding a lump on your horse can feel stressful, but it doesn’t always mean the worst.
When it comes to cancer in horses, there are more options than ever to manage equine tumors effectively, including innovative treatments like IsoPet®.
Trust your instincts and don’t hesitate to ask your veterinarian questions if you suspect your horse has a tumor. Remember, you’re your horse’s best advocate!
