Nail-Like Growth on Dogs

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Dog can have hard tumors called cornifying epitheliomas.
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If you're petting your dog and you feel something hard that looks like a nail or horn, don't panic. These tumors are known as cornifying epitheliomas. They might look unsightly but usually don't cause problems in the dogs who develop them. Take your dog to the vet for a definitive diagnosis and possible treatment options.

What are horn-like growths?

When you're petting your dog and you feel any kind of lump or bump that's not normally there, it's easy to start worrying about the worst possible thing. While cornifying epitheliomas can look a little like an animal horn, they can also look or feel like hardened spots or hardened cysts. Cornifying epitheliomas are also known as keratoacanthoma and infundibular keratinizing acanthoma, according to the Merck Veterinary Manual. Some people will also call these cutaneous horns, as "cutaneous" means skin.

"Cornifying" means looking like a horny substance, and "epitheliomas" is a medical word for a skin tumor that can be either benign or cancerous. A cutaneous horn on a dog will be a growth that sticks up from the skin surface. It can feel like a stick-like growth on a dog's tail. While they can develop anywhere, they often appear on the back, tail, and legs. They may also ooze pus or blood.


They will usually erupt from a hair follicle. Middle-aged dogs and certain breeds are most at risk for these growths. It is important to get them checked out because most of the time, they will be benign, but they do have the potential to turn into cancerous tumors or can become more widespread across the body. Humans can also develop similar horn-like masses.

Causes of cornifying epitheliomas

According to the Merck Veterinary Manual, dogs in middle age are most at risk of developing a cutaneous horn. Dog breeds affected by cornifying epitheliomas are Norwegian elkhounds, Belgian sheepdogs, Lhasa apsos, and bearded collies. Norwegian elkhounds and Lhasa apsos are at risk for having these tumors become more widespread. Michigan Ave Animal Hospital says a cutaneous horn on a dog arises through overgrowth of the dog's hair follicles. They are almost always benign.


A cause for why these develop is not known for sure. A chemical called B-catenin can turn skin cells into hair follicles as a dog develops, and overproduction of B-catenin can cause hair follicle tumors to develop. There is a genetic predisposition that makes these tumors more common in certain breeds of dog. The Veterinary Society of Surgical Oncology says that male dogs are more likely to develop these, and there has only been one known case in a cat.

Treatment of cornifying epitheliomas

Sometimes, dogs are annoyed by these growths and will attempt to bite, rub, or scratch them off their skin. If they do this, they can cause an infection or trauma to the horn site. In this case, your veterinarian might suggest surgically removing them. Sometimes, oral medications called retinoids can also help.


The Veterinary Society of Surgical Oncology says prognosis after treatment with surgery is good, as 71 percent of dogs have a complete improvement when treated with surgery, and 29 percent improve with treatment by retinoids, but the tumors commonly return after treatment is ceased.

PetCoach says to monitor the size, shape, texture, and appearance of any cutaneous horn on a dog. If it's causing your dog a problem, get it checked out to consider options for removal. Most cornifying epitheliomas are easily diagnosed and treated without the need for specialty veterinary care.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.