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The 12 Lumps (and Bumps) of Canine Skin

At the first examination,

my new vet said to me:

“Your dog’s lumps are cancer free.”

Any dog owner receiving that news would certainly breathe a sigh of relief. Finding an unexpected lump or bump might bring words such as “tumor” or “cancer” to mind, especially if you’ve lost a pet to cancer before. But the good news is that many lumps and bumps on or under a dog’s skin are frequently benign — as in not cancer.

Evaluation of skin conditions, including lumps, is a very common reason why pet owners sought veterinary care in 2017, according to Healthy Paws Pet Insurance. Here is a brief overview of 12 common canine lumps and bumps, so you can better understand what should concern you and what warrants a trip to the veterinarian.

1. Lipoma

The most common benign lump that dogs develop, a lipoma is a fat-filled tumor found under the skin of middle-aged or older dogs and is considered a natural part of aging. These soft, rounded, non-painful masses grow slowly and rarely spread. Any breed can develop lipomas, although overweight or obese dogs are more prone to them. Your veterinarian may recommend monitoring or removing a particular lipoma depending on where it’s located and whether it interferes with your dog’s mobility.

2. Histiocytoma

A histiocytoma is a red, button-like lump that’s often found on the legs of dogs less than 6 years old. Because they frequently go away on their own, histiocytomas are thought to be an overgrowth of a specific type of immune system cells that normally help protect the skin from cancer. If you find such a mass on your dog, you’ll want to have your veterinarian check it since histiocytomas can look similar to some other dangerous cancers.

3. Perianal adenoma

A perianal adenoma is a common tumor related to the sebaceous (oil) glands surrounding the anus. These lumps are mostly seen in intact (unneutered) male dogs, although they have been found in spayed female dogs. A perianal adenoma is often slow growing and non-painful, but may ulcerate and become infected on its surface.

4. Skin tag

Like aging people, older dogs can develop skin tags, which are harmless, fibrous growths often extending from the skin’s surface by a stalk. Dogs may have a single tag or many of them on their chest, legs, face, back, armpits or other areas. Skin tags can develop in any breed, although large-breed dogs may be at greater risk.

5. Sebaceous cyst

One type of superficial bump on your dog’s skin is a sebaceous cyst, which is a plugged oil gland in the skin. Basically, a sebaceous cyst is a very large pimple that is harmless to your pet and may feel like a raised bump. If left alone, it might go away without treatment, but may recur. If it bursts, a white, paste-like or cottage-cheese-like material is seen. Most sebaceous cysts don’t cause trouble, although they can become red and sore.

6. Abscess

The simplest way to describe an abscess is a “pocket of pus” located somewhere in the body. If located under the skin, an abscess may appear suddenly as a painful swelling that may feel firm or squishy like a water balloon. An abscess associated with the skin may be caused by a bite wound, either from an insect or another animal, or by an infected penetrating injury such as those caused by sticks or grass awns (sharp grass seeds). Your veterinarian will need to evaluate the abscess, drain it, flush the area with a sterile solution and prescribe antibiotics.

7. Hives

Hives on dogs, known medically as urticaria, are similar to those on people. Hives may appear as a rash of round, red bumps or as a collection of round or oval, raised bumps on the skin that itch. The underlying cause is a reaction to an allergen such as a bee sting or contact with a plant. Hives often resolve on their own if the case is mild; however, sometimes your veterinarian will want to administer an antihistamine or steroid to provide relief.

8. Warts (papillomas)

Like us, dogs can get warts, too. Warts — or papillomas, in veterinary-speak — are small growths that seem to pop up on the skin suddenly. Caused by a virus that’s highly contagious between dogs, warts are usually benign growths that occur on the face, eyelids, mouth, genital area, lower legs, feet, on the footpads and between the toes. Dog warts typically have a cauliflower appearance similar to the warts people get, and grow alone or in clusters.

9. Melanoma

Canine melanoma tumors result from unchecked growth of pigment-carrying cells known as melanocytes. These masses can be malignant or benign, so if you find one on your pet, you’ll want your veterinarian to evaluate it immediately. Melanomas of the skin, which are not caused by sunlight, tend to be benign and readily treatable through surgery, while very aggressive melanomas tend to grow around the mouth and on legs.

10. Mast cell tumor

Mast cell tumors (MCTs) are the most common skin cancer in dogs. Mast cells are a type of immune system cell found in skin and other organs and normally play a role in inflammation and allergies. MCTs are most often found in dogs older than 8 years of age and in specific breeds, including boxers, Boston terriers, Labrador retrievers, beagles and schnauzers. These tumors can look like many other lumps and bumps, which is why it’s important to have your veterinarian check them out. The appearance of MCTs varies tremendously with some occurring as small, freely movable tumors of the skin, while others may be large, ulcerated and hairless.

11. Soft tissue sarcoma

Soft tissue sarcomas are a large group of tumors that arise from connective tissue and are very invasive to surrounding tissues. They usually appear as a firm or semi-firm lump in the deep layer of skin, under the skin or within muscle. The lumps are often non-painful, have normal skin overlying them, and commonly develop on the legs, chest or abdominal wall. These skin tumors are common among middle-aged and older large breed dogs

12. Squamous cell carcinoma

A squamous cell carcinoma (SCC) is a locally invasive, cancerous skin tumor that develops from the primary cell type found in skin and mucous membranes. These tumors can be found in the mouth, skin or nail beds of dogs. The most common skin sites for SCC lumps are those areas that have less pigment, lack hair or have sparse hair. The canine skin form is associated with sunlight exposure and considered relatively slow growing. Dogs tend to be diagnosed with SCC when they are between 8 and 10 years old.

There are many other types and causes of lumps and bumps in dogs of all ages. If you find a mysterious lump, you should make an appointment with your veterinarian to have it evaluated. While it could ultimately be nothing to worry about, that harmless-looking mass could be a more serious problem. The good news is that early detection can lead to successful treatment.

RELATED POST: Pets Get Skin Cancer, Too!

The information in this blog has been developed with our veterinarian and is designed to help educate pet parents. If you have questions or concerns about your pet's health or nutrition, please talk with your veterinarian.


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