Sarcoids in Horses

Key takeaways

Sarcoids are a common, benign tumor on the skin of horses.

  • These masses can present anywhere on the skin, but are commonly on the face, chest, abdomen, genitals, and legs
  • The cause of these lesions are poorly understood, but they frequently appear following skin injury and may be related to bovine papillomavirus infection
  • Sarcoids can vary in appearance (flat or raised masses, smooth or roughened) and can become ulcerated, bleed, and have surface crusting
  • Diagnosis is by visual inspection but biopsy is the only confirmatory test
  • Treatment focuses on the removal of the benign mass, but may be combined with other treatments for best success
  • Other treatment options include immunotherapy, heat therapy, radiotherapy, and chemotherapy
  • Sarcoids commonly recur and prompt treatment while masses are small achieves the best prognosis
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A closer look: Sarcoids in Horses

Sarcoids are the most common type of tumor in horses and can be found anywhere on the skin. They are benign lesions that do not spread to other tissues, but they can become larger over time, bleed, and become infected if left untreated. In rare cases, these tumors can become aggressive and invade surrounding tissues. As such, a veterinary visit is recommended prior to worsening of the lesion.

Risk factors

The most common locations are the head (especially near the eyes), abdomen, chest, genitals, and lower limbs.

Sarcoids can present as a single lesion, or there can be several scattered on the body. Sarcoids can grow and become large, making treatment more challenging.

Sarcoids can also easily become injured, leading to a red, wet surface, and scabbing of the skin. Lesions that become infected, may be warm, painful, irritated, swollen, and red. Sarcoids that have been damaged may become larger or more invasive after an injury.

Possible causes

The underlying cause of equine sarcoids is yet to be identified.

There is strong correlation between bovine papillomavirus and sarcoids in horses. Horses may come in contact with the virus from flies or contaminated equipment or pasture.

Certain horse breeds (such as Quarter horses) appear to be overrepresented, suggesting a potential underlying genetic component.

In addition, sarcoids often appear following a bout of “proud flesh” on healing wounds, or following a previous injury.

Main symptoms

Sarcoids can vary in their appearance.

Testing and diagnosis

A physical examination is the first step in diagnosing sarcoids. A biopsy is required for diagnosis, although often tissues are not biopsied for submission until the sarcoid is removed for treatment.

Steps to Recovery

Treatment depends on the number and size of sarcoids and the location of the mass. Several treatments are available, and more than one modality may be used in combination to successfully treat sarcoids. Treatment options include:

  • Surgical removal
  • Applying ligatures
  • Laser removal
  • Cryosurgery
  • Heat therapy
  • Radiotherapy
  • Immunotherapy
  • Chemotherapy

Recurrence is very common in sarcoids. The best prognosis is achieved with prompt treatment when lesions are small. This is especially true for sarcoids in areas that are difficult to access surgically, such as near the eyes.

Left untreated, sarcoids may remain unchanged for years, or may develop into a more aggressive form of tumor. Very rarely, sarcoids disappear on their own without treatment.


As the underlying cause for sarcoids is not well understood, there are no specific ways to prevent sarcoids. Keeping horses in good health, free from injury in clean pastures, and maintaining regular veterinary visits are the best preventatives.

Are Sarcoids in Horses common?

Sarcoids are very common in horses.

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