Sarcoids are a type of skin tumour that commonly affect horses. They are the most frequent skin tumours found in equines, and while they are generally benign, they can be locally aggressive and cause cosmetic issues.

The exact cause of sarcoids is not fully understood, but they are associated with bovine papillomavirus (BPV) infection. They can affect all breeds, ages and occur in both sexes, all equids can be affected including donkeys and zebras. Typically, sarcoids are not painful or itchy, but they are locally invasive, persistent, and progressive.

They greatly in size and appearance. Over time they can increase in size and become ulcerated, infected and sore if left untreated. They can appear anywhere but are commonly found around the far, head, groin, upper thigh region, sheath and axilla (armpit). They can also develop secondary to damaged skin such as wounds and surgical incisions however this is uncommon.

Types of Sarcoids:

Occult Sarcoids

These are flat, hairless areas that may be mistaken for scars or skin infections.

Nodular Sarcoids

These appear as raised lumps or nodules on the skin.

Verrucous Sarcoids

These have a warty appearance.

Fibroblastic Sarcoids

These are more aggressive and invasive, often with ulceration and tissue destruction.


Veterinarians typically diagnose sarcoids based on their appearance during a physical examination however for a definitive diagnosis a biopsy sample of the lump must be sent to the laboratory for histopathological assessment.


Treatment of sarcoids can be a challenge and there is no universally effective treatment. The options available will depend on location, type and severity of sarcoid which is present alongside independent patients factors which we will always consider. We recommend treatment to minimise the risk of additional sarcoid lesion development especially in areas which is likely to be irritant to horses e.g. where tack may inflame the sarcoid.

Treatment options:

  • Ligation and banding

    Banding or tying off the sarcoid with a ligature can be tempting for sarcoids with a stem or ‘neck’. As blood supply to the sarcoid is cut off, the sarcoid slowly dies and drops off after a few weeks. However, this method should only be attempted by your vet, who can determine whether or not there is a root attaching the sarcoid to deeper tissues. Incorrect or inappropriate ligation can aggravate sarcoids, and must not be attempted at home.
  • Chemotherapy

    Topical and intra-lesional chemotherapy (mitomycin, cisplatin). There are drugs which can be injected into the sarcoid directly. The use of these chemotherapeutic agents do carry health and safety risks to humans, and therefore must only be used under the strict guidance of your vet. This type of treatment is best used alongside surgical removal of the lump to minimise the remaining tissue present.
  • AW4-LUDES (‘Liverpool’) cream

    A topical chemotherapy cream, the product is cytotoxic and should only be a applied by a veterinary surgeon. Sarcoids often look much worse before they improve. The treatment can be painful, and may cause some localised swelling around the sarcoid. This can be an effective method to remove sarcoids without horses requiring a general anaesthetic.
  • Photodynamic therapy (PDT)

    This involves the use of a topical cream, which is then exposed to light of a specific wavelength to activate the cream and destroy tumour cells. This method is widely used inhuman medicine, and a major advantage is the selectivity of the treatment – i.e. it avoids damage to healthy cells surrounding the sarcoid. PDT can also be combined with laser surgery for larger or more aggressive sarcoids.
  • Radiotherapy

    Radiotherapy uses radiation to damage DNA and protein in tumour cells. This often involves placing radioactive implants within the sarcoid. Good results can be expected with this method, but it is costly and only available at certain centres worldwide.
  • BCG vaccine

    The BCG vaccine is used to prevent tuberculosis (TB) in humans, and is injected into the sarcoid to stimulate the immune system, which then ‘attacks’ the sarcoid. Availability of the vaccine is often limited, but this method can be useful in cases where other methods are unsuitable (for example, sarcoids close to the eye).
  • Electrochemotherapy (ECT)

    This involves injecting the lesion with a chemotherapeutic drug (cisplatin) and then applying high-voltage electric pulses. This procedure needs to be carried out under general anaesthetic and is only offered at certain referral centres.

  • ‘Conventional’ surgical incision

    ‘Conventional’ surgical incision has historically had poor success rates, with tumours often recurring. These recurrent tumours are often more aggressive and rapidly growing than the original. This may be because of inadvertent ‘seeding’ of tumour cells into deeper tissue layers, or activating virus present in normal skin around the sarcoid during surgery.

    Obtaining good margins (removing healthy skin surrounding the tumour to ensure all the abnormal tissue is removed) can help prevent recurrence, but this does make closure of the wound challenging hence we now recommend adjunctive treatments alongside this.
  • Cryosurgery

    This involves applying liquid nitrogen to freeze and destroy any remaining tumour cells after surgical removal of the sarcoid, to decrease the chance of recurrence. Success rates are variable, and tend to be more successful on small, superficial lesions (e.g.occult sarcoids).
  • Laser surgery

    A major benefit of laser surgery is the reduced risk of contaminating the surgical wound with tumour cells as the laser damages tumour cells on the border of lesions helping to prevent the sarcoid recurring. The laser also works to seal off the wound bed and any blood vessels.

    This prevents bleeding, but does mean that these wounds must be left open to heal by ‘secondary intention’. The surgical wounds can look dramatic, but typically they heal well, with a good cosmetic outcome and a reduce chance of recurrence compared to surgical removal alone. Laser surgery may be performed under standing sedation or general anaesthetic, depending on the number, size, and extent of the sarcoids present.

    The typical location of many sarcoids  often necessitates a general anaesthetic to ensure full visualisation of the sarcoids so the surgeon can obtain adequate margins whilst maintaining patient and clinician safety.

    One further benefit of laser surgery is that all sarcoids can typically be removed in one fell swoop, avoiding the need for multiple repeat veterinary visits (such as to apply topical creams).


Various topical ointments and ‘natural’ remedies are available and marketed for the treatment of sarcoids. Many of these have little scientific evidence to back their use, and the safety and efficacy is questionable. As discussed above, inappropriate treatment or interference with sarcoids can aggravate the lesions, making them more aggressive, invasive, and more challenging to treat long-term.


When treating sarcoids please be aware they tend to recur, and multiple treatments may be necessary.

All the vets at Abbey Equine are happy to discuss any concerns about sarcoids, and the treatment options available. It is often possible to make an initial assessment based on good quality photographs sent via email, although a clinical examination is often necessary to fully assess the lesions and best advice on a course of treatment.

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Abbey Equine Clinic

Llansabbath Barns, Llanellen, Abergavenny, Gwent NP7 9BY
T: 01873 840 069

Abbey Equine Chepstow
Ride and Stride, St Arvans, Chepstow. NP16 6DN
T: 01291 444877

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Abergavenny Branch

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