Page 79 - Speedhorse May 2019

Sarcoids are skin tumors that can look like warts, proud flesh, or ringworm. Some are slow-growing and others are more aggressive.
SARCOID
Sarcoids are skin tumors that sometimes look like warts or proud flesh, or occasionally, look
like ringworm. There are several types of sarcoid. Some are slow-growing and some are more aggres- sive, but most of them do not regress. If you biopsy the lesion, the sarcoid often gets worse.
Smith generally sees the severe cases because he works at a referral hospital. “I rarely get
to see a dormant sarcoid or one that hasn’t
been previously treated. We may see one in a horse that is coming in for some other reason like colic, an orthopedic issue or some other problem. We might notice the sarcoid and mention it to the client, but generally don’t
do much about it because the horse is here for another reason and the owners don’t want to do anything about it,” he says.
There are six types of sarcoid: occult, verrucous, nodular, fibroblastic, mixed forms and malignant. Sometimes these are very distinctive, but often there’s a blurring of the margins. The hairless ones might have one little wart-like region, but there can be mixes of each. “We rarely see the classic forms by themselves,” says Smith.
The occult form is basically flat, hairless and often small and circular. “They are sometimes more extensive, but usually appear around the mouth or eyes, on the neck or medial aspects of the limbs, or on hairless regions of the body,” he says. “Sometimes they are hardly noticed. You may just see a little bit of pigment change in the skin. These are the ones I rarely get to see unless the horse comes in for some other reason.
“I was taught to leave occult sarcoids alone as some of these will regress on their own, but the literature has now gone back and forth regarding this. If they do regress, however, those horses are generally free of sarcoid for the rest of their lives. The body recognizes them, fights them off, and those horses develop an immunity.
“If they are extensive or in an area that’s not susceptible to trauma, I usually leave those alone
and have the owner just watch them to see if they get bigger. In an area that is likely to suffer trauma, like the girth region, we try to remove them. Most of the ones we see start out as small and quiescent but may be subject to some sort of trauma. If they are on the face or girth or along the horse’s side, the tack rubs them.”
Any rubbing or trauma may irritate them and cause them to grow. “Trauma is usually what results in progression from less aggressive forms,” he says.
Verrucous sarcoid growths are wart-like, grey and scaly, but extend deeper into the tissues than the occult sarcoid. “Sometimes they have a circular hairless patch around them that might look a little bit like ringworm, but because
they are warty there may be multiple different types of lesions together. Both the occult and the verrucous sarcoid are usually slow-growing and not very aggressive, but are susceptible to trauma that may stimulate them to grow. These are the ones that are usually mistaken for warts. They both have that typical hyperplastic warty appearance,” says Smith.
Nodular sarcoid can be type A or type B. “Type A has no cutaneous involvement, while type B usually has cutaneous involvement. They are both nodular in shape and just look like nodules underneath the skin, usually with the hair still covering them. They just look like a firm lump under the skin and you don’t really see anything that would make you think it’s a sarcoid. They generally form in specific locations, such as around the eye or the medial aspect of the legs,” he says.
Fibroblastic sarcoids are basically nodular but hairless. “They look like masses with ulcerated margins. They can either be pedun- culated masses (on a stem) or have a broad base. They may be ulcerated or look like granulomatous lesions. As such, they might be mistaken for any number of things, such as exuberant granulation tissue (proud flesh), squamous cell carcinoma, cutaneous habrone- miasis, pythiosis, etc. These growths can be very large and broad-based,” says Smith.
Mixed forms are basically a mix of verrucous, nodular and fibroblastic. “Some portions may have a specific appearance, whereas others go into the other types,” he says.
Malignant sarcoid is fairly rare. “Usually these are just a large, mixed form that is locally aggressive and continues to grow. I’ve seen some that have taken over an area and are rapidly growing, such as all the way down a leg or whole portions of the face. There is no real treatment for those. Trying to keep these horses alive could be grounds for animal cruelty, since these growths are very pruritic (itchy) and the horse will be miserable. The other types tend to be pain- less,” he says.
TREATMENTS FOR SARCOID
It’s usually best to leave most sarcoids alone, because if they are biopsied or removed, they often grow back in larger, more aggressive form. Surgery is one of the more common treatments, but the veterinarian may use cryotherapy first, which involves freezing the tissue to debulk it, which is what would usually be done in a human.
“We usually get to see the ones that people have unsuccessfully tried to treat and that haven’t responded to medical therapy, such as Xxterra, 5-Fluorouracil, Imiquimod, BCG, etc. I am not saying that these treatments haven’t been used effectively to treat some sarcoids. I only see the ones that recurred after these treat- ments have failed,” says Smith.
“I tell people that you shouldn’t just poke the bear. You either need to shoot the bear or leave the bear alone. Don’t poke it to see what happens! If the bear is asleep, leave it alone,” he says. Surgery is probably one of the more common treatments for sarcoids that have to be removed for some reason, but the goal is to remove all of it.
“The veterinarian would generally make
a decision regarding treatment based on the size and form of the growth. The fibroblastic sarcoids are more likely to be treated surgically. Location makes a difference also, since we can’t really excise the tissue around the eyes or on the eyelids,” he says.
For sarcoid lesions around the eyes, a com- mon treatment is an injection of BCG (Bacillus Calmette-Guerin), which is an immune stimu- lant. “This produces a lot of inflammation
and makes the area very angry, and hopefully stimulates an immune response so the body will fight the tumor,” says Smith.
If this works, the sarcoid becomes ulcerated and then falls off. Because of the swelling and inflammation, the horse may be put on drugs to help control that secondary inflammation. “One risk when using BCG is the possibility of side effects, which could include anaphylactic reactions,” he says.
Warts associated with equine papilloma virus 1 are contagious and can be transmitted between horses or spread by flies or some sort of fomite, such as tack, that takes the virus from one horse to another.
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EQUINE HEALTH