Horses are relatively resistant to melanomas. Equine melanoma is a form of cancer which develops in the melanin cells of the horse’s skin. Melanin is plentiful in the skin of grey and white coloured horses which makes horses of these colours more prone to equine melanoma than others.
Melanomas can occur in horses of any age, but are more prevalent as the horse ages. There are statistics which claim that almost 80% of white or grey horses will develop melanomas by the time they reach the age of 15 or thereabouts.
Quarter Horses, Thoroughbreds and Arabian horses are all breeds of horse that commonly develop melanomas, again, with the grey of these breeds being more susceptible.
CAUSES OF EQUINE MELANOMAS
The main cause of equine melanoma is the existence of excess melanin in the horse’s skin.
HORSE MELANOMAS SYMPTOMS/WHAT TO LOOK FOR
Equine melanomas are solid, smooth, hard, round black tumors usually located near the base of the ears, around the eyes, around the neck, under the tail and around the vulva or rectum. Generally they are not painful.
Unlike human melanomas, equine melanomas usually grow very slowly but they can, on occasion, metastasize and cause internal problems so it is important to always
have them checked by the vet
TREATMENT FOR MELANOMAS
Ask your vet to do a biopsy to ascertain an accurate diagnosis. Treatment could then take any of the following forms:
Do nothing - If the lump is small and not causing any other problems, it is usually best left alone. Some equine surgeons argue that operating on melanomas "activates" the cells and increases the chances of tumor growth. They recommend a cautious approach to the problem.
Oil Therapy - Applied topically, Frankincense Oil has been shown to reduce equine melanomas
Anti-ulcer tumour-shrinking medications - such as Cimetidine/ Cisplatin
Vaccines - Horses with a pre-disposition for melanomas may be prescribed Immune-stimulating vaccines. For Melanomas on the face legs and body, tissue-based vaccines made from the horse's own tumor cells have good results.
Radiation - External beam radiation is a cutting edge therapy for equine melanomas, particularly of the extremities.
Surgical Removal - A very small equine melanoma can be removed under local anesthetic using surgical excision. The horse will need to be sedated for this.
Laser Surgery - This might be recommended for larger melanomas or melanomas which are located in areas not easy to access using traditional techniques. Laser surgery is particularly good for cutting and sealing blood vessels and it makes dissection easier in areas where there is not a lot of extra skin. General or epidural anesthetic would be applied for this procedure.
For the future - Gene Therapy – this is a very exciting treatment for equine melanomas which is under development. In the future, gene therapy might be capable of manipulation of genetic signals to stop cells from becoming cancerous in the first place or turn off melanoma functions once they have started.