About Hamartoma in Dogs

It's perfectly natural for a dog to develop lumps and bumps through his life. Often those little nodules are no big deal. But it's hard to keep track of what's scary and what's harmless. If the vet told you those funny little bumps you found on Mopsy are hamartomas, relax: Hamartomas are benign.

Beneath your pup's fur is his skin, a complicated network of tissues and blood vessels working together to protect him. Though skin is a line of defense, it's not impervious to problems. In addition to cuts, burns, scrapes and bruises, it's also vulnerable to developing a wide variety of tumors. The epidermal hamartoma is a tumor unique to dogs.

The book "Practical Veterinary Technology" defines hamartoma as "a disturbance of tissue growth where the cells of a circumscribed area surpass the surrounding area." A simpler explanation is that one or more of the parts of your pup's skin is larger than normal. If Mopsy has a hamartoma, or nevus, she's had it since birth, as it's a "little extra" a dog is born with, though it may not be visible immediately. A dog may be an adult before a hamartoma presents itself.

Hamartomas vary in appearance, depending on where they're located. The epidermal hamartoma is a dark bump on the skin. A pup may have multiple epidermal hamartomas, also called redundant hamartomas, forming a line. Some develop into thick, dark skin folds; others resemble pimples. A sebaceous gland hamartoma, found where the sebaceous glands are conspicuous, is circular or elongated. The follicular hamartoma is a bump with large hairs growing out of enlarged follicular openings.

Though these little tumors are benign, vets usually recommend getting rid of them. Not only are they ugly, they carry a risk of developing secondary bacterial infection. Depending on where a hamartoma is located and its form, the vet may surgically remove it or use medication such as isotretinoin to treat it.