Melanoma Implications in Prepurchase Exams

A prepurchase exam can provide valuable insight on a horse’s health status, equipping you to make an informed investment decision. And while veterinarians commonly assess copious qualities from soundness to suitability, if it’s a stunning gray you have you have in your sights, it’s also important to consider whether the horse has melanomas and what risk these might pose to his future health.

When in their early stages, melanomas are small and can seem insignificant, but many are extremely invasive and even life-threatening. Harry Werner, VMD, of Werner Equine in North Granby, Conn., past president of the American Association of Equine Practitioners (AAEP) addressed the significance of identifying and describing melanomas during prepurchase exams at the 2013 AAEP Convention, held Dec. 7-11 in Nashville, Tenn.

Melanomas are common neoplasms (tumors) that develop in gray horses with age. Many are not particularly invasive, Werner said, while others can cause dysfunction or even death.

If a melanoma is detected during a prepurchase exam, “the practitioner must realistically inform the buyer without unfairly jeopardizing the sale by overstating the concern or understating in such a way as to incur unnecessary risk exposure for the examiner,” Werner said.

He described a case study of a 12-year-old grey Thoroughbred gelding to make his point. At the time of the prepurchase exam, the veterinarian identified a 1-cm melanoma on the horse's sheath and a 4-cm swelling of the left temporal area near the horse's ear. Radiographs of the head showed no significant findings. The report stated that the swelling below the left ear base was structurally insignificant at that time.

For two years the horse showed no signs of ill health, but then he began to demonstrate panic behavior (fortunately, only when not under saddle). The melanomas showed no further external changes as compared to their appearance at the time of the prepurchase exam. A thorough exam of the horse did not reveal any abnormal vital signs, general neurologic or cranial nerve function, orclinical pathology. However, on endoscopic examination of the guttural pouches (air-filled outpouches of the auditory system that connect the pharynx to the inner ear) the practitioner identified that the melanoma had spread over a large area. An MRI study of the horse’s head demonstrated bony destruction of the zygomatic arch (cheek bone) and melanoma invading a portion of the skull along with the middle ear and the temporal lobe of the brain.

These serious abnormalities were associated with aggressive melanoma progression, Werner said. The practitioner had informed his client that significant problems were not present at the time of the prepurchase exam, and he had no way of predicting how the melanoma would progress.

Because of cases like this, Werner urges veterinarians to identify and explain all abnormalities, such as melanomas, on prepurchase exams and to inform buyers of typical and worst-case scenarios to help them make informed purchasing decisions. "The veterinarian’s role,” said Werner, “is to provide perspective and explain the unpredictable biologic behavior of melanoma, the potential for local invasion, multiplication of additional lesions, as well as the potential for melanoma to target internal organs and tissues.” That said, in most horses, melanoma pathology does not often progress beyond external skin lesions, he added.

In summary, Werner said the veterinarian’s role in a purchase is to educate and inform through verbal and written communications, and the buyer should not hesitate to ask questions about his or her potential equine purchase.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.