What is Cancer ?
As the cancer begins to spread throughout the body it begins to metastasize and create additional masses. Some forms of cancer become apparent only when the cancer is in an advanced stage and outward symptoms begin to present.
Gray horses are very susceptible to nodular masses known as melanomas. These masses are usually seen under the tail, behind the jaw or in the eye. Most melanomas remain harmless to the horse, but there have been instances where they grow into invasive tumors and spread through the body.
In our society cancer is becoming more and more prevalent, not just in humans, but also in our animals. Horses are not the exception. Cancer occurs when normal cell growth changes and cells begin to multiply in a chaotic manner. These multiplied cells begin forming masses that will disrupt the normal functions of the body. Cancer can affect any part of the body.
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Symptoms of Cancer in Horses
If you suspect that your horse may have developed some form of cancer, schedule an immediate appointment with your veterinarian and have a full assessment done including bloodwork and biopsies, if possible. Signs to look for when suspecting cancer in your horse include:
- Evidence of a mass
- Enlarging or changing masses
- Swollen lymph nodes
- Chronic weight loss
- Distended abdomen
- Chronic vomiting
- Chronic diarrhea
- Dry cough
- Difficulty urinating
- Foul breath or odor from the mouth
- Refusal to eat or drink
Causes of Cancer in Horses
Just like in humans, it is difficult to determine the cause of most equine cancers. Researchers have determined that in the case of melanomas, the horse’s coat color is linked to a cell mutation that causes the melanoma to form.
Researchers are still working to understand why cells start rapidly multiplying causing mutations or masses to form. Some claim genetics plays a role, while others claim environment is the cause. Until researchers finally determine why cells begin mutating, cancer will still remain somewhat of a mystery.
Diagnosis of Cancer in Horses
Your veterinarian will begin with a full physical examination and will do several palpations along your horse’s body, searching for any masses that can be felt. After the initial assessment is finished, additional testing will be required to fully diagnose your horse.
Routine bloodwork will show if there is an elevation of the blood calcium concentration. An elevated blood calcium concentration is called hypercalcemia. If elevated, it could point toward cancer.
Your veterinarian will want to do some form of imaging to see exactly where the mass or masses are located and if it has metastasized; X-rays and ultrasound may be utilized.
A biopsy will be taken of the mass to determine the type of cancer. This will give your veterinarian an idea of how advanced the cancer has become. By taking a biopsy of the lymph nodes or the actual mass, it can be determined if the mass is malignant.
Treatment of Cancer in Horses
It has been determined that many of the same treatments used in humans for cancer work for horses diagnosed with cancer. This includes surgical removal of the mass, chemotherapy, and radiation.
Depending on the location and size of the mass, surgical removal may be an option. Your veterinarian will determine through testing and imaging if your horse is a good candidate for surgery. Laser surgery has been used with success in the treatment of cancer in horses. It is used to cut out the mass and seal the blood vessels, thus promoting faster healing.
Researchers have developed a serum that is tissue based and made from the cells of your horse’s mass. This serum has had great success in treating melanomas. There has been limited success in treating other forms of cancer in horses.
Radiation has been used to shrink existing masses and reduce the chances of the cancer spreading.
Recovery of Cancer in Horses
Horses diagnosed with cancer will always be given a guarded prognosis. If the cancer has been found while still in the early stages and immediate treatments have begun, your horse has a much better chance of fully recovering. Follow the treatment plan set by your veterinarian to ensure the best possible prognosis for your horse. Keep your veterinarian informed of any changes to your horse’s health so the treatment plan can be modified.
In horses that have been diagnosed with cancer that is in the later stages or has already metastasized, supportive care is suggested to keep their quality of life as high as possible. In these cases, the treatments would probably have little to no effect on the cancer and eventual euthanasia will be recommended.
Cancer Questions and Advice from Veterinary Professionals
Recently my Oldenburg mare had to be put down do to a tumor wrapped around her small intestine. How long would it take for something like this to develop? Why didn't I notice any major symptoms? I took her to the vet that morning due to colic symptoms but I hadn't noticed anything more than that. Any advice for what to look for in the future?
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