Epidermoid in Horses

What Is Epidermoid in Horses?

An epidermoid is another name for a cutaneous cyst, which is made up of cells from the top layer of the skin. Epidermoids are typically benign and are a fairly common skin problem in horses. They usually remain small but may grow slowly over time. Epidermoids can look very similar to other masses on the horse's skin, like sarcoids, so it is important to have them examined by your veterinarian as soon as you notice one.

Symptoms of Epidermoid in Horses

• Swelling just under the skin

• Redness

• Hair loss

• Occasionally, small amount of clear discharge from the site

Epidermoids can be found on any area of the horse’s body.

Causes of Epidermoid in Horses

Epidermoids usually form as a secondary health issue related to an abnormality of skin cells shedding. This causes the cells to accumulate under the top layer of the skin and create a small, firm swelling or mass. Sometimes these skin cells will also produce normal oils of the skin, which is why discharge might be seen.

In some horses, an inflammatory process secondary to an insect bite or other trauma may be involved. In others, there might be a genetic predisposition that causes breeds to form more epidermoid cysts, but this process is not completely understood.

How Veterinarians Diagnose Epidermoid in Horses

Epidermoid cysts are often diagnosed based on examination by your veterinarian. If they have concerns your veterinarian may recommend sampling the mass using a fine needle aspirate (FNA) technique or a biopsy. Usually if they don’t sample it, they will at least recommend that you monitor the bump for any changes in size, number, or shape.

Treatment of Epidermoid in Horses

Often, epidermoids don’t require any treatment. Your veterinarian will likely recommend that you monitor the site for any changes. If the cyst becomes large or is draining often, it can either be drained or removed by your veterinarian. Occasionally, if the cyst is in a location that is in repeated contact with tack or blankets, topical anti-inflammatories such as Animax® or Surpass® may be recommended to help decrease the swelling.

Recovery and Management of Epidermoid in Horses

In most cases, nothing needs to be done about an epidermoid cyst except to monitor it. If surgery is required to remove it, normal wound healing treatments will be required. This will include keeping it clean, protected, and using either topical or systemic antibiotics.

Epidermoid cysts cannot be prevented but thankfully are usually just a cosmetic issue that does not affect the horse’s health.