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What is Peri-Ocular Sarcoid?

A periocular sarcoid is the most common form of tumor found in horses.  The cause can be associated with trauma to the area as well as if your horse is suffering from bovine papillomavirus.  Tumors can develop in multiple forms and with differing textures.  Typically it can be diagnosed with a combination of physical appearance and histopathology.  Treatment can vary between surgical excision, chemotherapy, radiation, and immunotherapy.  Prognosis of recovery will be determined by size, shape, and the chance of recurrence.  If treated properly, prognosis of recovery is considered fair.

If your horse has a growth near or around his eye, you should contact your veterinarian as soon as possible for evaluation. Treatment must be undertaken and may include medication and surgery.

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Symptoms of Peri-Ocular Sarcoid in Horses

The appearance of the eyelid tumor may appear:

  • Smooth
  • Nodular
  • Crusted
  • Ulcerated
  • Nodular
  • Pedunculated 
  • Hairless or altered hair appearance
  • Miliary nodules
  • Plaques 
  • Spherical
  • Ovoid 
  • May have a well-defined outline

Types

An equine sarcoid is the most common skin tumor diagnosed in horses.  The periocular region is one of the more common places to find the tumor.  It is a locally invasive fibroblastic type of skin tumor and are classified by their appearance and clinical behavior.  Sarcoid tumors can also develop on the ear pinnae, ventrum, extremities, lips, and neck.

Causes of Peri-Ocular Sarcoid in Horses

Bovine papillomavirus (BPV) types 1 and 2 are also associated with the development and pathogenesis of sarcoids in horses.  However, it is believed this virus alone is not the cause.  Scientists suspect other factors such as skin trauma or infections to be considered a potential risk for development of this disease.

Diagnosis of Peri-Ocular Sarcoid in Horses

Your veterinarian will start by performing a full physical exam on your horse.  While your main concern may be his eye, she will want to check the rest of his body for more growths.  By appearance alone, your veterinarian can give a presumptive diagnosis.  For a definitive diagnosis, she will need to perform a histopathology.  However, this can be tricky as a biopsy type incision can exacerbate the lesion and induce rapid reproduction of the sarcoid cells.  

The histopathology report of a sarcoid tumor typically comes back positive for immature fibroblasts, epidermal acanthosis, hyperplasia and hyperkeratosis.  These results can be confused with a fibroma or fibrosarcoma and therefore a specialist will be best to read it.  This will also help to rule out other possible diagnoses of abscess, cyst, melanoma, neurofibroma and other conditions with similar appearance. 

To ensure there are no other eye conditions affecting your horse she will examine it with her ophthalmoscope.  This gives her a look into his eye, magnified with proper views of the cornea and retina.  In addition to just examining it, she may want to perform a tear stain test to check eye lubrication levels and want to perform a fluorescein stain test to check for ulcers.  

Your veterinarian may want to perform general blood work in order to ensure there are no underlying medical conditions occurring at the same time.  A chemistry panel and complete blood count will give the veterinarian general information on your horse’s internal organ functions.  She will want to check that all his values are normal; abnormalities can indicate other issues that may complicate his recovery process.

Treatment of Peri-Ocular Sarcoid in Horses

There is no exact treatment for a periocular sarcoid in your horse.  Since the location of the tumor is in a very delicate place around the eye, surgical treatment options are limited.  Conventional excision may be an option as well as carbon dioxide (CO2) laser removal.  There are also other treatment options including chemotherapy, radiotherapy, hyperthermia, cryotherapy, immunotherapy, antiviral agents, and topical immune modulation.  You may need to go to a specialist to have this procedure done.  

Recurrent masses are said to be more aggressive with more rapid growth and extensive local invasion.  Radiation is the most common treatment for sarcoid tumors in horses.  The non-recurrence rates are much better than other treatment types for this tumor.  

Some studies have shown therapeutic vaccinations containing chimeric virus-like particles have shown some tumor regression.  Other treatments may include supportive treatment to keep your horse comfortable and to ensure no secondary issues develop.  Any eye condition can deteriorate quickly; your veterinarian will want to monitor it closely.

Recovery of Peri-Ocular Sarcoid in Horses

The severity of the tumor will play a role in the prognosis of recovery.  Also, the recurrence of the tumor will also be a factor in his prognosis. However, if treatment is available and the protocol is completed properly, prognosis is fair.  At the first sign of recurrence, it is imperative it be reevaluated immediately.