Cancer in Horses


Fortunately cancer is relatively rare in horses. Early detection of some cancers can be found during routine blood work because of certain secretions. These secretions are generally due to an internal cancer. Swiss researchers continue to study this means of early detection.

Here is a list of some of the cancers that though rare, can affect horses.

Malignant melanomas – Statistics show that 80% of gray horses more than 15 years old will develop a cancerous tumor of the skin. This type of cancer can be found internally or can appear on the skin as growths. Depending on location, size and number of tumors, most can be surgically removed. The most common skin tumors are called Sacroids.

Gastrointestinal tumors – Most stomach tumors are malignant. These tumors can be removed surgically unless the cancer has spread throughout the abdomen.

Granulosa – Theca Cell Tumors are found in the ovaries of mares. Signs are failure to conceive and aggressive behavior. Prognosis is good with early detection and removal of ovary or ovaries.

Squamous Cell Carcinoma – These are tumors of the outermost layer of skin. Tumors are removed through chemotherapy, cryosurgery, radiation, anti-inflammatories.

Osteosarcoma – Bone cancer is rare in horses. Prognosis with OSA is poor.

Thyroid Tumors – Most thyroid tumors are benign and don’t interfere with a horse’s life. If they are malignant, then treatment is removal of the thyroid gland.

Pituitary Gland Tumors – Most are usually benign and associated with Cushing’s Disease. There is no surgical method at present to remove a pituitary tumor. However drugs have been used successfully to normalize hormone levels.

Chemotherapy administered to horses can be tricky. For one thing, the treatments are expensive, Because of the amount of chemo necessary to treat such a large animal, it can be dangerous for the person administering it. By no means should treatment not be given and if the owner can afford the cost, treatment is generally given at an equine clinic in a veterinary school.

Cisplatin, a chemotherapy drug was used but caused vomiting. Since horses cannot vomit, there were serious side effects. Studies have shown that administering cisplatin directly into the tumor along with a substance that keeps the drug at the tumor site have had positive results.

The best medicine in the fight against cancer is feeding a nutritional diet, supporting the immune system and regular checkups.

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