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Horse Cancer: Symptoms, Common Types, and Surviving

Last updated: April 29, 2022

By: Miles HenryFact Checked

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Cancer, in general, is a scary word. Horses are no exception to this rule! However, it’s important to know the facts about cancer and horse health so that you can stay informed and keep your horse healthy.

Horses, like humans, can get a variety of cancers. The most common are sarcoids (tumors), lymphoma, and melanomas (types of skin cancer). Horses with cancer may experience various symptoms depending on the kind they have. Further, some equine cancer is treatable while others are not.

There are many types of horse cancer, but thankfully some can be successfully treated if caught early. The possibility of successful treatment makes it essential to determine the type of cancer your horse has, so it can get the proper care they need.

Picture of a horse being evaluated for cancer.

Horse cancer

Cancer starts when something goes wrong, and a horse’s cells multiply, and old or abnormal ones don’t die off as they should. The result of this is various diseases that fall under the umbrella of cancer.

Horses have a high chance of surviving cancer if they are diagnosed early. It’s important to keep an eye out for symptoms like tumors or lumps in various parts of the body and talk with your vet about any concerns that you might be having.

If a vet can diagnose your horse and get treatment started early enough, there is a good chance that surgery for some types of cancer will be successful. However, if left untreated for too long, chances decrease significantly because it spreads quickly through the body.

So the best practice is to regularly check your horse for tumors and be aware of cancer symptoms. While horses can’t tell us whether there is something wrong, it’s our job as their owners to make sure we’re looking out for them and knowing what signs indicate illness so that we get medical attention sooner rather than later.

Common types of horse cancer.

Sarcoid tumors in horses

Equine sarcoids are the most common skin tumor in horses. These tumors can grow larger but metastasize (travel to other parts of the body). The presence of equine sarcoids on your horse’s skin is irritating and will bust open from rubbing against tack or interference with everyday riding.

Busted tumors bleed profusely, which poses a risk for fly contamination worry as well as a local infection. Sarcoid tumors are most often found around the eyes, lower abdomen, and around the chest and ears.

To treat a sarcoid tumor typically requires its removal. However, this procedure often has little to no effect on stopping future growths of these tumors in that area.

There are many ways to remove sarcoid tumors. One is to cut them off (under general anesthesia), and another is to freeze them. And sometimes, vets use lasers or ligatures, which cut the tumor’s blood supply until it dies out.

Lymphoma in horses

Lymphoma occurs when a group of harmful cells starts growing out of control – it can start anywhere in the body and spread throughout if not controlled. It most commonly occurs in the lymph nodes, spleen, stomach, or chest.

These tumors proliferate and metastasize quickly, so a vet should start extensive blood work and immunotherapy drugs right away. Lymphoma is malignant, which means it cannot be cured, but treatments can help to slow it down.

When horses have lymphoma, they often display symptoms such as coughing, difficulty breathing, loss of appetite, and lack of energy. Once a horse begins showing signs of cancer, it should see a veterinarian immediately.

The vet will perform blood tests to determine if your horse has lymphoma or other cancer types, then develop an appropriate treatment plan based on the diagnosis.

Treatments available for lymphoma cancer in horses are limited. Cancer treatments that work in humans may not be effective for horses, and some drugs are toxic to them.

Chemotherapy is commonly used, but it can have severe side effects even with the best veterinary care. Monitoring success rates vary widely depending on where the tumor is located and how far it has progressed.

two.year .old

Melanoma in horses

Melanoma cancer is a very dangerous form of skin cancer that can be found in horses. It can affect horses of any color, but it is most often found in older gray horses.

This cancer usually appears on the underside of a horse’s tail or genital areas and sometimes around its head. Arabians and Lipizzaner breeds are also more susceptible to this disease than other breeds.

Early diagnosis through monitoring skin lesions is key in reducing mortality rates when treating equine melanomas with surgery. Researchers are exploring the use of a canine melanoma vaccine as a potential treatment for equine melanomas.

You can do some things to help prevent melanoma cancer, such as providing shade for your animal to escape the sun or using sunscreen and fly masks with UV protection.

Some suggest a diet rich in beta carotene (such as carrots) may help prevent skin cancers in horses. Finally, you can have your veterinarian perform a routine physical examination on your horses because catching melanoma early is essential.

Squamous cell carcinoma in horses

Squamous cell carcinoma is a type of skin cancer horses that most often develops in areas near mucous membranes. It is most prevalent in horses with pink skin, but any horse can get this cancer if it gets too much sunlight.

Squamous cell carcinoma is the most common type of tumor affecting animals‘ eyes and eye structures. If left unchecked, it can spread to surrounding tissues.

However, prevention is simple: providing shade for your animal means they can escape harmful ultraviolet rays, which is the cause of this cancerous growth.

Squamous cell carcinomas usually manifest in horses at around 12 years old, but luckily there have been successful treatment methods used on horses when caught early.

As a responsible horse owner, you should check it regularly for skin lesions. Squamous cell carcinoma is more common and less serious than melanomas.


Hemangiosarcoma is a rare type of cancer for horses. It is made up of cells that line blood vessels, and it can be found in any part of the body but most commonly affects the spleen, liver, and heart.

Splenic hemangiosarcoma is identified through symptoms such as respiratory distress, lethargy, and muscle weakness. It is usually treated with surgery to remove the tumor, followed by chemotherapy or radiation therapy. However, even with treatment, horses typically do not recover and rapidly decline.

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Do horses die of cancer?

Horses do die of cancer. When the disease quickly spreads throughout a horse’s body, many have no chance of survival, and owners are often left with a difficult decision whether to put the animal down.

How long can horses live with lymphoma?

After an extensive study, researchers found that cancer treatment for horses is not as effective on some types of lymphoma as others. However, the mean survival time ranges from 7.5 to 13 months.


  • Equine Sarcoids-Veterinary Clinics of North America: Equine Practice Volume 14, Issue 3, December 1998, Pages 607-623
  • Equine lymphoma-Equine Veterinary Education (EVE) Volume23, Issue 4 April 2011 Pages 205-213
  • Squamous cell carcinoma in horses.-Journal of the American Veterinary Medical Association, 01 Jan 1976, 168(1):61-62 PMID: 1245449 
  • Disseminated Hemangiosarcoma in the Horse: 35 Cases- J Vet Intern Med 2000;14:105–109
  • Melanomas in horses.-Yale J Biol Med. 1973 Dec; 46(5): 646–649.