Q&A: Treating sarcoids

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Q: I am very worried about my nine-year-old, 17hh Hanoverian/Thoroughbred mare. Over the past six months she has developed five sarcoids on her mammary glands.Can you tell me what they are? I’ve been told to buy chemotherapy cream. Is this safe?

Jo Holmes replies: Sarcoids are the most common form of equine skin tumour andcan occur almost anywhere on the body.

The cause is unknown: certain viruses are suspected but they are not contagious.However, some horses seem to have a genetic predisposition to develop them. Sarcoids are rarely painful and occur as solitary masses or in spreading groups.

Besides their unsightliness, they can be a nuisance if they are damaged by tack, becoming open sores that attract flies and infection.

You don’t describe your mare’s sarcoids but there are several types:

  • Type one appear like warts on the surface of a horse’s skin.
  • Type two can grow quite a height above the skin surface, looking similar to proud flesh.
  • Type three appear as a combination of types one and two.
  • Type four are slow-growing, insidious and flat, looking more like thickened skin.

If a skin abnormality is noticed, it should be watched carefully over a period of two to three months for speed of growth.

If it gets beyond the size of a 10p piece, surgical removal can be almost impossible, since on certain parts of the body there will not be enough spare skin to cover the defect.

For small, well-defined sarcoids, surgical removal is the treatment of choice, provided a large margin of healthy skin can also be removed to prevent recurrence.

Sarcoids are notorious for recurring with twice the vigour and invasiveness of the original lesion – ifa small amount is accidentally left behind – so it is best to catch them early.

Taking a biopsy of a sarcoid (removing a small piece for laboratory analysis to confirm diagnosis) is inadvisable – either remove it all or not at all.

It may not be possible to remove the five sarcoids on your mare surgically. Other possible treatments include chemotherapy and radiation therapy. Some vets also use cryotherapy – liquid nitrogen freezes the tumour cells – butthis method can be less successful.

You may choose to leave the sarcoids alone if their growth rate slows dramatically and you do not plan to breed from your mare. They are not likely to restrict her in any other way. However, from the current speed of their growth and the possibility of them spreading to her belly, you would be wise to do something.

Chemotherapy involves small doses of highly toxic drugs, such as arsenic, which, when applied directly to the tumour cells, kill them off.

You can be supplied with the appropriate drugs, in the form of a cream, through your own vet. Your mare must be easy to treat as it may take months to fully eradicate the tumours.

Radiation therapy can only be performed in a veterinary hospital and is often used on tumours where other forms of treatment have failed or are not possible.

Radioactive rods are attached across the tumours for a specified length of time (up to several days) and the horse is kept in isolation.

The tumours should slowly die off and shrink over the following months. This is the most potent form of treatment and the most expensive, so try other methods first.

The sarcoids may spread to other organs but your mare will remain fit and healthy. She should only suffer the inconvenience of being treated.

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Originally published on horseandhound.co.uk