Vet Vibes: Sarcoids

A small well-defined sarcoid with a wide margin of unaffected skin.

VET VIBES Equine sarcoids: what you need to know

If you’ve noticed a wart-like lump on your horse’s skin, it could very well be a sarcoid. Veterinarian Dr DOUG ENGLISH discusses types and treatments.

The equine sarcoid is by far the most common cutaneous neoplasm (skin growth) in horses. It affects horses of all ages, and was first described by Jackson in 1936. He introduced the term ‘equine sarcoid’ because the growth looked like a sarcoma, which is a cancer of the connective tissue.

An equine sarcoid is a tumour of the skin only, it does not spread to internal organs. Most affected horses are normal in every other aspect except those with large lesions. A sarcoid doesn’t seem to have any significant correlation with age, sex, or breed, and incidence varies between two to six per cent of the equine population, including donkeys, mules, and zebras.

are most likely the primary cause of sarcoids. BPVs are spread by flies from any lesion to any wound, even one that’s small and barely noticeable. Your horse doesn’t have to be in close proximity to cattle for spread to occur, because flies can be blown around over distances of many kilometres.

Types of sarcoids

There are six broad types of sarcoids. While most are slow growing, all types have a high propensity for recurrence and often interference or injury can make them change to a more aggressive type.

With such a tendency for change, most vets are reluctant to use a biopsy to define them because of the risk of activating the sarcoid and it becoming more aggressive. Most are recognisable by observation anyway, and any warty growth that has been present long term is going to be a sarcoid – and that’s true in almost 100 per cent of cases. To determine whether or not

the growth is a sarcoid, a good size sample is needed from centre of lesion to achieve an accurate result.

A needle biopsy is not worth doing.

The six types of sarcoids are as follows (keeping in mind that any type can unpredictably change to another):

Sarcoids can appear on anywhere on the body (Image by Alexandra Beckstett).

Examining a sarcoid prior to removal.

After cleansing around the general area, a local anaesthetic ensures the procedure is painless.

1. Occult: small circular

hairless skin spots 2.Verrucous: warty and scaly 3.Nodular: large spherical nodules 4.Fibroblastic: fleshy with prominent ulceration 5.Mixed: types two, three, and four all combined 6.Malignant: an extreme form with deep local tissue invasion

(Prof Derek Knottenbelt, University of Liverpool). Treating a sarcoid

No single treatment is consistently effective and recurrence is always possible. There are many treatment options, with no standout success achieved with any of them - radiation possibly being the best. That a few cases do resolve spontaneously does imply that there may be some immunological processes involved.

• Surgical incision: Only suitable for small well-defined lesions where there are wide margins of unaffected