There are many factors linked to the occurrence of sarcoids including the bovine papillomavirus, (wart virus of cows), and a genetic predisposition with some breeds. The tumour is sometimes spread by flies landing on sarcoids and then onto an open wound on the same or another nearby horse. Sarcoids can remain consistent, not changing size for many years, or be locally very aggressive and become large quite suddenly. They do not tend to spread around the body.

Sarcoids can occur in a variety of forms, as single or multiple lesions. Currently, there are 6 recognised types:
• Occult: flat, grey, hairless, often circular and persistent.
• Verrucose: grey, scabby, or wart-like appearance that contains small lumps, possible surface ulceration and covering an irregular area.
• Nodular: multiple, discrete, solid lumps of variable sizes.
• Fibroblastic: fleshy mass with a thin stalk or wide, flat base. Bleed easily.
• Mixed: mixture of two or more types.
• Malevolent: rare, aggressive tumour, spreads extensively through the skin.

Sarcoids tend to develop at sites of previous injury and scarring, but can occur anywhere on the body- most commonly on the head, sheath, chest and abdomen.

fibroblastic sarcoid ear

occult-sarcoid flank

Diagnosis is usually made based on the clinical appearance of the sarcoid. A definitive diagnosis can be made by biopsy, that is, taking a sample. Sometimes this aggravates the sarcoids and triggers excessive growth.

It is vital to consult your veterinarian before trying to treat a sarcoid, otherwise is can be aggravated. Currently, there is no single effective treatment for all types of sarcoids. Ideally all tumours should be treated early on when they are small. Therapeutic options include surgical removal, cryotherapy (freezing with liquid nitrogen), chemotherapy drugs injected into the tumour and many topical treatments. We often joke that when there are many options for treating something, many of them don’t work, so it’s important to come up with a therapeutic plan with your veterinarian.

There is also a factsheet on sarcoids available on this website under Your Horse and Factsheets.

If you think your horse has a sarcoid and would like to discuss potential treatment options with one of our veterinarians please call us on 02 6241 8888 or get in touch via email at