The 5 Most Common Types Of Cancer In Horses

Nobody wants to think about their equine friend getting cancer, but it is something that many horse owners are forced to deal with. Are you familiar with the most common types of cancer in horses and what you should be watching for? We've compiled a list of the 5 most common types of cancer in horses.

#1 - Melanoma

Occurring in any dark-skinned horse, melanoma is most common in gray horses; with a large percentage of gray horses over the age of 15 developing melanomas. Appearing any time after the age of 4 or 5, growths that appear on younger horses are more likely to become malignant more quickly. Lumps may be individual or in groups.

#2 - Squamous cell carcinoma

This type of skin cancer in most common in areas of unpigmented skin. This is especially true in places with little hair covering, such as around the eyes, mouth, anus, or genitalia. Horses with white faces are especially prone. Sunny regions produce even higher numbers of tumors around the eyes. Growths often start on the third eyelid. This type of cancer is treatable if caught early enough.

#3 - Sarcoid tumors

One of the most common skin tumors found on horses, sarcoids usually don’t spread internally. Even if they become huge, they usually stay in their local area without affecting other parts of the body. They can be removed with surgery or treated with chemotherapy, though they are known to return if not all of the affected tissue is removed.

#4 - Reproductive system cancers

Breast cancer (mammary neoplasia) is not very common in mares. When it does occur, it’s usually malignant and has a poor prognosis for long term survival. Testicular tumors are known in stallions but are not very common and are usually benign. Male horses are prone to prostate cancer, which is becoming more of a problem as more horses are being exposed to abnormal internal and external factors.

#5 - Lymphosarcoma

Since the lymphatic system is spread throughout the horse’s entire body, this is the most common and generally most aggressive form of cancer. The four types of lymphosarcoma are generalized, intestinal, mediastinal, and cutaneous. Cutaneous lymphoma is the least deadly.

If you see any changes in your horse, whether they are behavioral or physical, you should always seek immediate vet care. Many cancers have better survivability the earlier they are caught.