written by: Leah Strassman
What are Sarcoids?
Equine sarcoids are a type of tumor that occurs on the skin. They are the most common tumors
seen and account for approximately nine out of every ten skin tumors. They are non-malignant
(i.e., they do not spread throughout the body) but do grow larger and often spread and multiply
locally. They can cause irritation, and interfere with tack. If knocked or rubbed their surface can
bleed, which can lead to insect problems and local infection.
What do they Look Like?
There are different types of sarcoid and they can vary quite widely in appearance. Flat (sessile)
sarcoids are round to oval flat areas of roughened, hairless, irregular skin. The skin feels slightly
thickened. Fibroblastic sarcoids are irregularly round, raised, firm lumps. They are usually
smooth and hairless at least over part of their surface but smaller ones are sometimes covered
with normal-looking skin. If the surface becomes damaged, or often after normal growth, the
tumor will ulcerate and bleed, leading to scab formation. Verrucous sarcoids appear wart-like
with an irregular surface. A horse may have different types of sarcoids at the same time and
mixed-types also occur. Sarcoids can grow to become very large (over 3.1-3.9" (8-10 cm)),
although most remain smaller than this.
How are they Diagnosed?
Sarcoids can be similar in appearance to other skin tumors (e.g., fibromas, mast cell tumors and
non-pigmented melanomas) and it is necessary to submit a sample (biopsy) or the whole tumor
to a laboratory for analysis for a precise diagnosis to be made. If possible, it is usually preferable
to remove the whole tumor in the first instance for laboratory examination. This avoids a
second surgical procedure after diagnosis and avoids traumatizing the tumor still 'in situ'
potentially encouraging its spread.
How are they Treated?
There are several options for treatment of sarcoids and more than one treatment may be used
at the same time. The important thing to remember is that sarcoids have a great tendency to
recur either at the site of removal or nearby. The choice of treatment will depend upon several
- The number and size of the sarcoids present
- The part of the horse affected
- The facilities and drugs available
- Financial considerations
What methods of treatment are there?
Sometimes it might be best to simply monitor a small sarcoid that has recently developed and is
not causing any interference with tack etc watching for any signs of development or growth. In
a lot of cases sarcoids may remain unchanged for many years in which case neglect is the
correct option. If the sarcoid changes or begins to grow, an alternative treatment strategy is
If is often possible to remove a sarcoid by simply cutting around it using a local anesthetic and
stitching the resulting wound. This is easily done if there is only a solitary tumor or there are
only a small number present and there is enough free skin left afterwards to close the wound.
Tiny sarcoids may be removed, leaving a small open wound to heal by granulation.
Approximately 50% of sarcoids treated this way re-grow subsequently.
Applying ligatures or rubber rings
It is possible to remove the bulk of some sarcoids, especially those with a short stalk or neck, by
fixing a tight ligature around its base or applying 'elastrator' rings. The ligature cuts off the
tumor's blood supply and it dies away or falls off usually 10 days to two weeks later. This
method is useful for short-term control of relatively large sarcoids on the inside of the
hindlimbs or abdomen but does not usually give long-term resolution of the problem.
The sarcoid may be frozen by using liquid nitrogen or another appropriate freezing agent, that
causes the tissue to die away. If the sarcoid is large, most of it can be cut away first (de-
bulking), leaving only the base to be frozen. This method is more effective at preventing
recurrence than surgery alone, but often results in the development of patches of white hair
due to damage to hair follicles.
Where available, surgical laser treatment allows the bulk of the sarcoid to be removed and the
base eroded either in one step or the base eroded after de-bulking the main mass. There is
minimal bleeding because the tissues are burnt, but healing can be slow. Scars will form but
hair color is usually unaffected.
Radioactive beads or wires
This highly specialized technique is not widely used but can be effective particularly for eyelid
sarcoids where it is necessary to try to save the eyelid. The radioactive treatment shrinks the
tumor and may disfigure the eyelid.
BCG is a vaccine produced from the bacterium Mycobacterium bovis for immunization against
tuberculosis. It may be injected into the sarcoid tumor(s), often with useful results. Several
injections over several weeks or months may be required. This treatment is aimed at provoking
an immune reaction from the horse's body to destroy or reject the sarcoid tissue. It is most
commonly used for eyelid tumors because, if effective, it allows the eyelid to be saved.
Specially-prepared cytotoxic (tissue killing) creams have been widely used to treat sarcoid
tumors. These attack the abnormal cells in the sarcoid and are often highly effective, but can
also damage healthy tissues. They must be used with great care, especially over bony areas or
blood vessels and nerves. They can be used on smaller and flat sarcoids or larger ones after
surgical de-bulking. The cream can only be supplied to and used by a veterinarian. Another
cytotoxic drug (Cisplatin) is available but must be injected into a sarcoid to be effective. This is
another highly specialized technique as dose and pattern of injections varies with size and
shape of the sarcoid. Both techniques cause local inflammation and scaring is variable,
depending on the size and location of the sarcoids.
No matter which treatment option is chosen it can take many months to remove some sarcoids
and the effect might not be permanent. Treatment may need to be repeated or changed if new
Should I Adopt a Horse with Sarcoids?
You shouldn’t necessarily rule out adopting or buying a horse with sarcoids but you should go into it
carefully and understanding the ramifications.
First of all, consider the severity of the current issue- if there are a couple of small sarcoids that do
not interfere with tack that will be a different consideration than if there are several large ones
that do interfere with tack or movement.
Next, consider what you want to use your horse for. Are you looking for a performance horse to
show? A lightly used trail horse? Or maybe just a companion horse- the answer to that question
tells you the impact the sarcomas are likely to have.
Lastly, treatment can get expensive – are you in a position to afford to treat them, insurance will
not cover preexisting conditions.
KEY SARCOID FACTS
- Sarcoids are very common.
- Geldings appear more frequently affected.
- Although sarcoids are a type of tumor, they do not spread internally.
- The tumors can arise at any cutaneous (skin) site but there are some sites more
prone to occurrence: chest, groin, sheath, belly, and axillae, around the face
(especially around the eyes and mouth), and at sites of previous wounds.
Sarcoids have a high chance of recurring even after certain treatments.