Cancer is much less prevalent in horses than in humans, dogs, cats, and many other species. It is uncommon, but not impossible, for a horse to develop cancer that affects internal organs. Horses are far more likely to develop cancer of the skin or tissue close to the surface of the body. By learning about the most common cancers in horses, you may be able to recognize a potentially cancerous growth while it is still in the early stages of development.
Proper horse care and preventative health products can also play a role in supporting your horse’s overall well-being. Many horse owners rely on products available through trusted retailers like 1-800-PetMeds, including supplements and wellness items found in their Horse Supplies category.
Melanoma
Around 80 percent of gray or pale colored horses will develop melanomas. This condition is usually seen in horses over seven or eight years old, although younger horses can also develop them. Most melanomas begin as benign growths and may become malignant over time. However, it is impossible to determine whether a melanoma is dangerous simply by looking at it. Some become malignant quickly, others take years to progress, and some never metastasize.
Melanomas may appear as a single lump or in clusters. They typically begin as firm lumps beneath the skin and eventually turn black or gray in color. These growths often appear around the eyes, genitals, or mouth, though they can also affect the guttural pouch, lymph nodes, heart, lungs, and other internal organs.
While melanomas often have a recognizable appearance, they can still be confused with other skin conditions. For that reason, it is important to have your veterinarian examine any suspicious growth and confirm the diagnosis through a biopsy. If the melanoma is determined to be benign, your veterinarian may recommend monitoring it over time.
If treatment becomes necessary, the most effective options may include:
- Surgical removal
- Cryotherapy freezing treatments
- Chemotherapy
There is also a vaccine called ONCEPT, originally developed for dogs, that may help stimulate a horse’s immune system to attack melanoma cancer cells.
Supporting your horse’s skin health and immune system can also be helpful as part of an overall wellness routine. You can explore immune and skin support products in the Horse Vitamins and Supplements category.
Squamous Cell Carcinoma
Squamous cell carcinoma, often referred to as SCC, is the second most common type of cancer affecting horses. It is most frequently found on or around the eye, though it may also develop in the mouth or on the genitals.
SCC often begins as a small lesion or sore that may appear weepy or crusty. When it affects the eye, excessive eye discharge may be one of the earliest warning signs. As the condition progresses, the lesion may develop a clustered, cauliflower-like appearance.
This cancer does not usually spread widely throughout the body, but it can damage nearby tissues such as the eye itself or the lymph nodes beneath the jaw. Treatment options often include surgical removal or chemotherapy, depending on the location and severity of the tumor.
Sun exposure is believed to play a role in the development of SCC, especially in horses with lighter skin around the eyes. When it appears on the genitals, poor hygiene may also contribute to the condition.
Horse owners often use protective gear, such as UV-blocking fly masks, to help reduce sun exposure. You can find several protective options in the Horses category.
Lymphosarcoma
Lymphoma, also known as lymphosarcoma, is the most common blood-related cancer in horses. Despite that, it remains rare overall and affects less than 0.5 percent of horses worldwide. It does not appear to favor a particular breed but is most often seen in young adult horses between four and ten years old.
In many animals, lymphoma causes noticeable swelling of the lymph nodes. In horses, however, this symptom is not always present, which makes diagnosis more difficult.
One form called cutaneous lymphoma causes visible lumps beneath the skin, although this version is relatively uncommon. Other forms affect the internal organs and may cause a wide range of symptoms, including:
- Anemia
- Difficulty breathing
- Coughing
- Weight loss
- Lethargy
- Diarrhea
- Decreased appetite
- Abdominal pain
Because these symptoms are so broad, lymphoma may be more common than previously believed. A horse that appears to have colic, for example, may actually be experiencing abdominal pressure caused by masses on internal organs.
Treatments such as surgery and chemotherapy may be used in some cases. Unfortunately, the prognosis for lymphoma in horses is often poor.
Preventing Common Cancers In Horses
Horses naturally spend much of their time outdoors in the sun. Continuous exposure to ultraviolet light can increase the risk of certain skin cancers, especially in horses with light colored hair and skin.
To help reduce risk for sensitive horses, consider the following steps:
- Limit sun exposure during the middle of the day when UV rays are strongest
- Use UV protective fly masks to shield delicate areas around the eyes
- Maintain regular grooming and hygiene
- Monitor your horse for new lumps, bumps, or lesions
It is important to take any unusual growth or sore seriously. If you notice unexplained symptoms, consult your veterinarian for an examination. While cancer in horses is relatively uncommon, early diagnosis greatly improves the chances of successful treatment. Many cancers in horses are treatable and sometimes even curable when detected early.
