Equine melanoma is a type of skin tumour commonly seen in older grey horses. By the time a grey horse reaches 15 years old, about 80% will have at least one melanoma. While typically associated with grey horses, melanomas can develop in horses of any colour, though they tend to be more aggressive in non-grey horses. These tumours often appear as black, firm lumps under the skin and can grow in various areas, including under the tail, near the genitals, around the mouth, or even in the eyes. Some may remain harmless, but others can spread and cause health issues, including pain or difficulty with basic functions like eating or defecating.

Melanomas are linked to genetics, especially in grey horses. A specific mutation that causes their coat to grey also increases their risk of developing these tumours. Certain breeds, like Lipizzaners and Pura Raza Española (PRE), show higher rates of melanoma due to their genetic makeup. Initially, melanomas may appear as small, black nodules. Over time, they can grow and spread locally or through the body. Larger tumours may ulcerate, abscess, or interfere with bodily functions. Managing these tumours early can prevent complications.

There are several treatment options for equine melanomas. Surgical removal is the most effective way to treat accessible melanomas. Even large tumours, up to 20 cm in diameter, can be removed successfully with minimal complications. However, surgery doesn’t stop new tumours from forming elsewhere. Injecting chemotherapy drugs directly into the tumours has shown some success, though these treatments are usually combined with surgery for better outcomes. Another method, electrochemotherapy, uses electric pulses to enhance the effect of chemotherapy drugs on tumours. While promising in some cases, its success is inconsistent, and it’s often used for tumours that cannot be surgically removed.

Other options include immunotherapy and vaccines. Treatments like the Oncept melanoma vaccine aim to stimulate the immune system to fight the tumours. While they may slow tumour growth, they don’t consistently shrink existing tumours. More studies are needed to confirm their effectiveness.

A newer treatment showing promise is betulinic acid, a compound derived from white birch bark. Betulinic acid has shown anti-cancer effects against equine melanoma cells. In one study, horses treated with a topical form of betulinic acid experienced a significant reduction in tumour size over three months. The treatment was well-tolerated with mild side effects. More work is required before this treatment could be recommended clinically, but it may prove to be a useful, practical treatment for accessible lesions.

There’s no one-size-fits-all solution for managing equine melanomas. Early surgical removal remains the most reliable approach for accessible tumours. For more advanced or inaccessible melanomas, options like chemotherapy, electrochemotherapy, or experimental treatments might offer hope. Continued research is essential to develop more effective and accessible therapies.

Grey horses are at higher risk for melanomas, and early detection is key. Surgical removal is the best option for treating melanomas when possible. Horse owners are encouraged to talk to their veterinarians about all available treatments, including newer options like betulinic acid or immunotherapy. Regular monitoring of your horse’s health can help manage this condition effectively. By staying informed and proactive, you can help ensure your horse leads a comfortable and healthy life despite the challenges of melanoma.