Case of the Month




A 7 year old thoroughbred mare was examined after the owner reported a growing mass under the left eye. The mass had doubled in size in the year that they’d owned the horse. It was hairless and would easily become ulcerated and bleed.



The mass in question was found to be a sarcoid, the most common skin neoplasia (cancer) that we see in horses.  Sarcoids are commonly found on the face/ears, the groin and abdomen, and sometimes develop at a prior wound site.  There are six different types of sarcoid appearance that range from a flat wart to ulcerated fibroblastic tumors.


Generally sarcoids are locally aggressive tumors that do not spread widely or to other organs. There is a rare type of sarcoid that will spread extensively throughout the skin.


Sarcoids have been shown to be associated with the bovine papilloma virus and flies are sometimes implicated in spreading that virus between horses.


Taking a biopsy of a sarcoid may cause it to become more aggressive so a biopsy is not always indicated and a biopsy was not necessary in this case.


Treatments can vary based on what type of sarcoid the horse has. In this case of a periocular sarcoid, a series of immunostimulant injections were done into the tumor using a product that is a cell wall extract from a specific type of bacteria.  This injection causes the tumor to be broken down over time.



In this case the tumor regressed completely over a period of 8 weeks. 3 injections were done under light sedation during that time.  After the first injection the horse experienced mild swelling around the tumor but no other negative effects were seen.  The horse was able to continue her normal workload during treatment.


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