What is Squamous Cell Carcinoma?
Squamous cell carcinomas start out as small, red bumps that can be barely noticed on areas of unpigmented skin. These bumps may seem harmless, but they are actually a form of skin cancer that can be fatal to your horse. If you find an abnormal lump, a skin irritation that does not heal, or if your horse is showing changes in behavior, the sooner you get your veterinarian involved the better. Squamous cell carcinomas will grow and possibly metastasize to other parts of your horse’s system. Surgical removal, as well as therapies such as radiation and chemotherapy, can be utilized in the treatment of this condition. The earlier the treatment begins, the better your horse’s prognosis of recovery is.
Squamous cell carcinomas are one of the most common types of skin tumors found in horses. These appear most commonly in the eye, on the genitalia or in other areas of unpigmented skin. If you notice an abnormal bump or growth on your horse, call your veterinarian immediately for a consultation.
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Symptoms of Squamous Cell Carcinoma in Horses
Symptoms may start out as barely noticeable and then develop into secondary complications. Symptoms may include:
- Small sore
- Raised bump
- Foul odor
- Noisy breathing
- Lack of appetite
- Ocular discharge
- Bleeding from the penis
- Difficulty urinating or defecating
Bumps develop most commonly on places of the body where mucous membranes meet the skin.
The most common types of skin tumors in horses include sarcoids, melanomas, and squamous cell carcinomas. Squamous cell carcinomas can be ulcerative or proliferative masses found most commonly in unpigmented areas of skin. Tumors will start out small, but can grow very quickly if not caught and treated.
Causes of Squamous Cell Carcinoma in Horses
Squamous cell carcinomas first appear where the mucous membranes meet the skin. These places also happen to be unpigmented skin that has very poor protection from the sun’s UV rays, a major factor of the cause. As the tumor grows, it can spread to the lymph nodes and then metastasize to other parts of the body. The location of the tumor can lead to unusual symptoms not seen in the most typical cases.
Diagnosis of Squamous Cell Carcinoma in Horses
Your veterinarian will want to do a full physical on your horse. As an example, while the tumor may obviously be in his eye conjunctiva, the veterinarian will want to check the rest of his body for other tumors. Your veterinarian may want to take a biopsy sample for testing in order to appropriately diagnose what type of tumor it is. If there are other areas being affected by similar tumors, she may want to collect samples of those as well.
If she believes the tumors have metastasized, your veterinarian may want to take a chest radiograph to check your horse’s lungs. If the tumors have metastasized to his lungs, it will help the veterinarian determine her course of treatment. If your horse is experiencing a lack of appetite, she will also want to check his GI system for tumors as well.
Blood work will be conducted to see if the internal organs are functioning properly. The blood work will also show how your horse’s body is responding to the tumors and whether he will need additional therapies added to his treatment regimen.
Treatment of Squamous Cell Carcinoma in Horses
Treatment for your horse will have multiple variables. The location of the tumor and economic concerns will play a large role. Surgical removal is a common form of treatment of squamous cell carcinomas in horses. Additional therapies may also be utilized at the same time of surgical removal to ensure the entire tumor was removed. Cryotherapy, laser therapy, photodynamic therapy, brachytherapy, radiation and chemotherapy can be used in conjunction with surgery.
Follow up treatments, such as cisplatin injections, will need to be done after surgical removal of the main tumors. Since squamous cell carcinomas tend to recur, your veterinarian may need to cut and inject the area multiple times to ensure the tumor has been completely removed. If you do not do the follow up treatments properly or wait too long, you may have to start the entire treatment process over or your horse may never properly recover.
Recovery of Squamous Cell Carcinoma in Horses
Early diagnosis is important when it comes to squamous cell carcinomas. If recognition is delayed and therefore causes treatment to be delayed, the chance of recurrence and metastasis increases. If the condition is caught early and treatments are started quickly, prognosis of recovery is good. However, if it is left untreated and allowed to metastasize to other areas of the body, your horse’s prognosis declines greatly and the condition can even lead to his death.
Squamous Cell Carcinoma Questions and Advice from Veterinary Professionals
My pony Strawberry has recently had a lot of discharge and she will start pacing her pen. My grandma isn´t concerned about her, but I am. I don´t think being lonely would be the problem with her pacing, she has my two other horses to keep her company. My grandma doesn´t really get the dentist out there at all, so her teeth are pretty bad, along with the other horses. Do you think that could be the reason why she is pacing her stall all the time? She seems to have had a lot of discomfort lately, and will do anything in my power to try to help her. Do you think you could help me?
Thank you Dr. King, I hope she is okay too. I will talk to my grandma about it, and hopefully she will get the vet out there as soon as possible.
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Hi - My horse has a swollen area near the corner of his eye. My vet is relatively new - he said we could do a biopsy, but I asked if the treatment would be different and he said no. He seems convinced it's a squamous cell carcinoma because it's red and bumpy and there's lots of discharge. He said there were two alternatives, depending on what is found once we have the horse doped up and can do a thorough exam. If it's in the third eyelid, he suggests removing it. If it's just the flesh in the corner of his eye, he'd freeze it. Other people are telling me that I should have a biopsy in case it's not cancer and to find out what kind it is. Another barn mate has a friend whose vet did chemo drops in the eye and cleared it up without any cutting or freezing. I'm going nuts trying to figure out what to do. Any suggestions? What are the odds that it's not cancer? Would a biopsy help to find out what kind? Should I start with chemo drops? I don't know how severe it is. Has been building up with discharge and redness increasing.
Thanks Dr. King. I hope so, too.
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I have been doing quite a bit of research on equine cancer and became increasingly concerned about whether my horse has cancer around his eyes. He is a bald-faced APHA with one blue and one brown eye. We had taken him to professionals at a university near where we live when we first bought him and they ruled out cancer then. Ever since we bought him he has always had some degree of sunburn around his eyes with peeling skin (Not an excessive amount).He has also had discharge of both eyes but not enough to make me worry until now.His eyes have recently been releasing more discharge than usual. Other than that the skin around his eyes has stayed the same since we bought him and took him to the vet. I was wondering if the longer days, since winter is ending and spring is coming, where we live resulting in longer exposture of his eyes to the sun (Making his eyes discharge more) is what is causing it or if we should take him back to the vet for further evaluation. Thank you.
I am happy that he is OK.
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Our mini mule has had 2 surgical excisions for squamous cell carcinoma on her hoof (frog area) and now above her coronary band onto her leg. She has been treated multiple times with cisplatin beads. We live in Northern Connecticut and are looking for other options, such as Fluorouracil, Bleomycin, mitomycin-C, teletherapy, cox-2 inhibiters, or laser therapy with Nd:YAG or diode. Do you know who would offer any of these treatments in an area which is not located on the other side of the country? We have been using Rhinebeck Equine in Rhinebeck, NY, but I don't think he has anything further to offer her. Thank you for any resources you can provide! Linda Scofield
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