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Equine Sarcoid Frequently Asked Questions
Table of Contents
  1. What is a Sarcoid?
  2. What causes Sarcoids?
  3. Are there different types of Sarcoid?
  4. How common are Sarcoids?
  5. What treatments are available?
  6. Are Sarcoids contagious?
  7. Are Sarcoids being researched?
  8. What is the prognosis for a horse with Sarcoids?

What is a Sarcoid?

A Sarcoid is a tumour involving connective tissue {ie. muscle, sub-cutaneos tissue, etc.}. A tumour which may appear outwardly similar is the Lymphoma {cutaneous lymphosarcoma}, which involves the Lymphatic system {glandular system to you or I}. Both these tumours are distinct from epithelial tumours {carcinomas melanomas}. The sarcoid begins as a small wart-like growth, but may progress, through stages of rapid growth, to be the size of a tennis ball. Generally being dry scaly masses that may ulcerate bleed, the main problems with a true sarcoid are those of secondary infection physical interference e.g. with tack. The key difference between sarcoids lymphomas is that sarcoids are benign, lymphomas are malignant. Sarcoids exist in several forms, see below for details.

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What causes Sarcoids?

Sarcoids are believed to be caused by a virus, though I have failed to find a detailed explanation from any source. It has also been shown that Sarcoids occur more often in the older horse on sites of previous trauma. See below for notes on contagion. From my own experience I noted that sarcoid growth appeared most in spring early summer; obviously there are many factors that could precipitate this: dietary change, increased UV light, fly strike, changing routine / stress levels to name but a few. I was unable to conclude which factor(s) was the cause.

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Are there different types of Sarcoid?

Yes, Sarcoids can be split into several types ....

Typically these are dry golf ball size lumps, though size may vary considerably.
They most often occur on head, chest shoulder/ under-leg. Normally lacking hair,
they are not difficult to spot.
If a verrucous sarcoid grows splits or is otherwise physically damage then it may progress to this type. This is the type that tends to cause more problems as it grows bleeds; some have been known to reach the size of a small football. Ulceration, fly-strike secondary infection can all be issues to be tackled. Growth rates do vary with these sarcoids sometimes lying dormant for several years.
These are a flat form of sarcoid which again may become the fibroblastic type if damaged.
As previously mentioned, sarcoids can be confused with other growths. Identification is important since many of the other growths are malignant and could therefore spread internally. Biopsy by an expert is the most accurate form of diagnosis, but this has its drawbacks see under "Treatments".
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How common are Sarcoids?

Sarcoids are relatively common particularly in older horses, though severe cases are considerably less common. Fortunately the more serious cutaneous lymphosarcoma is relatively uncommon.

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What treatments are available?

Various different treatments are available ...

Traditional Surgery Traditional Surgery
Physical removal of the tumour has been the normal practice. However there are multiple drawbacks to this technique.
1] A high percentage of cases recur within several years.
2] Growth can be accelerated by the physical trauma of the surgery.
3] Possibility of "seeding" the tumour elsewhere by cell debris. esp. if diagnosis is incorrect tumour is malignant.
4] Possibility of significant scarring or physical disability due to site of tumour operation.
Cryosurgery Cryosurgery
This is a technique whereby the area to undergo surgery is repeatedly fast frozen to destroy all tissue before surgical removal. This decreases the likelihood of recurrence seeding. However the technique is not suitable for use near sensitive tissues such as the eyes.
Radiation Therapy Radiation Therapy
This technique is similar to that used to treat human cancer patients; the affected area is irradiated using a localised source. The drawbacks of this treatment are :
1] Localised side effects of radiation
2] Requirement for specially trained staff to administer treatment.
However the treatment may be particularly suitable around the eyes, where surgery is impossible.
Immunotherapy Immunotherapy
A technique to activate the horse's own immune system against the tumour cells. Two different methods can be used:
1] Injection of BCG vaccine - Multiple injections into the tumour over a period of some weeks.
2] Introduction of Sarcoid tissue - Deactivated Sarcoid cells introduced under skin to build immune system over several months.
These treatments are only suitable for small tumours do take sometime to work, however they do have the advantage of being relatively non invasive.

Chemotherapy Chemotherapy
Again a technique originally developed to treat human cancer patients. A variety of chemical agents are being studied, the main characteristics being:
1] Application is topical or injected into tumour - this minimises the systemic effects of the toxins on the patient.
2] Typically the chemical agents are toxic heavy metal compounds in an inert carrier base.
3] A dosage balance must be struck between tumour irradication toxic side effects.
4] Beneficial where surgery is impractical or in conjunction with surgical techniques

Other Techniques Other Techniques remedies
A list of misc. other treatments that I am aware of. Thankyou to all who have emailed me with their experiences.
1] Laser Vapourisation - Use of a hot laser to destroy tumour tissue, typically in conjunction with surgery.
2] Constriction - Application of a band such as a castration ring to remove "hanging" tumours. cf. traditional wart removal.
3] Tea Tree Oil - Applied topically has apparently been of help in some cases.
4] Thuja - Can be given orally as tablets or applied topically as an oil. Thuja is a Chinese herbal remedy that is sometimes available from natural health stores. I have one report of some success with this, on sarcoids that were not responding to traditional treatments; thankyou Michelle. If anybody else has used it please let me know.
5] Hyperthermia (Heat Treatment) - localised intense heating of tumour cells using a special instrument. Thanks Holly for this the next.
6] Dermex - A herbal paste made from a plant grown in Wyoming, USA. (Don't know what the plant is, please let me know if you do). Applied topically, has been successful on an awkward occult sarcoid. Also useful for reducing fibrblastic size before other treatments.

Author's Comment, "Seems to me that someone needs to research what the active substances in Tea Tree, Thuja and Dermex are. If you're a Vet. Researcher, why not spend some time on this?"

Success rate defined as % of treated horses with complete removal and no recurrence after 3 years.

Note. This table is merely a rough overview of results that I have read. It is intended as a rule of thumb as such, is not statistically accurate.

Traditional Surgery




Radiation Therapy







Variable but often 85%



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Are Sarcoids contagious?

Sarcoids are not considered contagious, however they may be spread by contamination with living tumour cells. In other words any mechanism that might scrape cells off the tumour then place them back in another site, could lead to the formation of a new tumour. As previously mentioned, physical trauma to a sarcoid may accelerate the tumour activity.

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Are Sarcoids being researched?

Yes, there is considerable effort being made to research into these tumours. Some of the establishments are listed below:
Leahurst Veterinary College, Liverpool University, UK
Equine Research Centre, Newmarket Cambridge University, UK
University of California, USA

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What is the prognosis for a horse with Sarcoids?

This depends upon the severity of Sarcoid occurrence. Often small Sarcoids will remain relatively unobtrusive cause few problems for a horse. On the other hand severe cases that resist treatment may require that the horse be destroyed on humane grounds. Research is continually improving the success rate of treatment; this combined with the fact that Sarcoids are benign tumours, means that in the majority of cases there is little risk to the horse's long term well being.

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Hints & Tips

This section includes a list of suggestions that are either not covered elsewhere or that require emphasis:

1] Make regular inspections of any abnormal lumps bumps on your horse.
2] If you discover an abnormality, don't panic, keep a record of any changes, this will help your vet.
3] Identification is critical, make every effort to have a positive ID of the tumour type before making any treatment decisions. cf. Risk of aggravation from biopsy.
4] If a Sarcoid is identified consider whether or not it requires treatment. These tumours may not concern your horse if left alone, yet can become problematical after interference.
5] If treatment is necessary discuss the various options and their drawbacks. Not all vets are aware of the full facts, discussing things with your vet can only be helpful to you both.
6] Try to minimise any external aggravation of the tumour - I found that a mixture of Gammexane cream sunblock lotion helped to reduce summer problems without irritating the Sarcoid tissue.
7] If you don't succeed at first, try again. Keep in touch with research developments, if your horse doesn't respond to one treatment, consider a different one.

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Author's own experience with Sarcoids

I have created this FAQ with the intent of helping others to understand a little about the problems of Equine Sarcoids. It is dedicated to Flare, my 15-3HH Thoroughbred Mare who lost her 6 year fight with Sarcoids Lymphomas, in the summer of 1995. Below I will briefly describe the progress of her condition:

1] First noted a blemish under her front right leg. Over a period of 6 months this developed to golf ball size with several other small lesions near its base.
2] After 12 months surgery became necessary due to chafing subsequent bleeding during exercise. Also several small blemishes had appeared on hind legs near mammary glands.
3] Traditional Surgery discovered further tumours nested under visible ones. A total of 20 or so "Sarcoid" tumours were removed.
4] Surgery followed up with Laser Vapourisation techniques.
5] 12 months without sarcoids, 1st 3 months spent recovering from surgery.
6] After 1 year recurrence of Sarcoids noted, initial development relatively fast, also more widespread.
7] 2nd Veterinary opinion suggests that Lymphomas are involved as well as Sarcoids. Options: A] Cryosurgery but high risk of increasing internal malignancy of Lymphomas or B] allow mare to enjoy life as long as possible hope for research breakthrough.
8] Option B chosen, Constriction used to control faster progressing tumours. However, ulceration hampers attempts to do this.
9] A further year or so passes, daily topical treatment to avoid secondary infection has been continual but Flare seems quite happy until recently.
10] Leahurst undertaking trials of Topical Chemotherapy treatment and having considerable success. Flare spends 1 year undergoing trial Chemotherapy.
11] Flare's tumours have decreased slightly after 1 year of sporadic chemotherapy, but her body cannot withstand anymore therapy due to the chemical toxicity. I should point out that during the year I watched as many Sarcoid cases were cleared up using the Chemotherapy, however Flare's case was the most resistant one encountered.
12] I decide that Flare should be allowed to live out her life running free in the paddocks of my home in Wales. She spends a happy 9 months before I have to have her put down due to her deteriorating condition. She is sorely missed.

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