A very common equine tumor type is the sarcoid. These locally invasive neoplasm's occur in the dermis (skin layer) and subcutaneous tissues. There seems to be a predilection for the head, ears and limbs although they may be found anywhere on the horses body. Over 70% of sarcoids occur in horses less than 4 years of age. One third of affected horses have multiple lesions. The sarcoid lesion comes in four clinical forms: Flat (occult), verrucous (warty), fibroblastic (proliferative) or a mixed form of verrucous and fibroblastic.
This sarcoid is on a front leg
These tumors do not metastasize (spread systemically) but they may wax and wane or spread on a local or regional basis. The flat type of sarcoid will usually remain static unless traumatized, and if traumatized such as with biopsy, may change in type and behavior and become fibroblastic or proliferative. These lesions present a clinical challenge since we know that "angering" them through surgical trauma may in fact create a worse problem than we had at the onset. So in many cases we will opt for benign neglect and do not biopsy or remove these lesions. Still, although some of these lesions are singular and in a position on the body that they are not causing any problem, many of them are either in an area that are troublesome to the horse, such as an eyelid or the muzzle, or are spreading aggressively.
When considering biopsy of a suspected sarcoid tumor we are actually considering tumor removal, since as mentioned earlier, we attempt not to "anger " the tumor tissue. So as a practice we perform an incisional biopsy and remove the complete tumor growth with a wide margin of skin. Sarcoids have been treated with radioactive isotope implants, various chemotherapeutic intralesional injections, excision, split thickness skin grafts, cryosurgery, hyperthermia treatment, topical caustic creams and various immune stimulants both systemic and intralesional.
At our clinic we have treated sarcoids with all of the common methods and after considerable deliberation among all of the doctors we are unanimous in our feelings that no one treatment is our treatment of choice. The decision of which treatment or combination of treatments, to utilize for any particular case, is dictated by the location, the size and growth rate of the tumor. In many cases not only is an initial treatment plan considered but a contingency and or follow up plan is in place.
Should your horse have a tumor, call EMS to schedule an analysis of its condition and severity.