11 Types of Lumps, Bumps and Lesions Under Your Dog’s Skin

It can be disturbing to cozy up to your canine companion and feel lumps and bumps under your dog's skin. It's even more disturbing to discover that a lump or bump has ulcerated or burst, and your dog's skin has become inflamed.

Dog owners naturally think of a cancerous tumor (also known as a malignant tumor) when they feel lumps and bumps under their dog’s skin. Owners may assume that it's an early detection of cancer instead of a benign tumor or benign growth. The good news about skin growths is that most kinds are not cancerous. A few types of skin growths don't require treatment. 

Only your veterinarian will know for sure if a skin abnormality has the potential to become a malignant tumor. We can give you some pointers on what to expect from your vet's diagnosis.

1. Lipoma

Lipomas are the most common kind of lump or bump that appears under canine skin. One survey of veterinary visits found that about 10% of canine lumps and bumps are lipomas.

Lipomas are benign fatty tumors and don’t contain very many cells of any kind. They are mostly little bags of fat that don’t become cancerous.

Not all dogs get lipomas. They are most common in mixed breed dogs, Weimaraners, Doberman Pinschers, German Pointers, Springer Spaniels, miniature Chihuahuas, and Labrador Retrievers. Older dogs that are over nine years in age are 17 times more likely to develop lipomas as dogs under six years old. Dogs that are overweight are nearly twice as likely to develop lipomas as normal-weight dogs.

Your dog won't need treatment for lipomas unless they interfere with activity. But only your vet will know for sure that a lump under the skin is a lipoma.

2. Abscesses

Abscesses are also a common but non-cancerous lump found on and under the skin of your dog.

Abscesses are basically a pocket of pus. They can feel firm and feverish, or they may feel squishy like a water balloon.

The most common underlying cause of abscesses in dogs is bites by other animals. Sometimes, owners may not know about the animal bites until they see the new lump on their the pet's skin. These can also result from wounds by sharp seeds, nails, burrs, or grass with "stickers” penetrating the skin.

Abscesses are a reason to take your dog to the vet. Your vet will evaluate the treatment options for the abscess and probably drain it with a fine needle, flush it with saline solution, and prescribe antibiotics.

Untreated abscesses can destroy tissues under the skin and cause a systemic fever in your dog even after they have burst and released their foul-smelling contents. Abscesses can progress to a condition called “skin fold pyoderma” in Spaniels, Bloodhounds, Shar Peis, Pekingese, Pugs, Boxers, and Bulldogs.

3. Histiocytomas

Histiocytomas are a type of benign tumor that appear as button-like red lumps usually found on the lower legs of dogs less than six years old. They are believed to be a collection of a specific kind of immune cells that protect your dog's skin from cancer. But because they look like certain types of aggressive cancers, they should be checked out by your vet.

4. Papilloma

Papillomas are warts caused by canine papillomaviruses passed from dog to dog. A papilloma appears about 30 days after the skin is infected.

These small cauliflower-like growths pop up suddenly on the mouth, face, eyelids, genitals, footpads, genitals, or between the toes. They can appear as a single growth or in clusters. 

Canine papillomas are unsightly, but it is very rare for them to progress into a form of cancer known as canine squamous cell carcinoma. Although this only occurs in severe cases, check with your vet about surgical removal just to be on the safe side.

5. Sebaceous Cysts

Sebaceous cysts are basically large pimples. When they burst, they release a skin oil called sebum which will have a consistency and color similar to tiny curds of cottage cheese. Sebum is created by the sebaceous gland which is a gland in the skin that opens up into a hair follicle.

It's easy to tell that sebaceous cysts aren't cancerous. They have a regular, round shape. Cancers usually have uneven edges. Sebaceous cysts have the same color as surrounding skin, cancers usually don't. 

Sebaceous cysts can be firm or jiggly. They aren't likely to cause problems unless they become infected. Often, they will go away on their own after a few months.

6. Perianal Adenomas

Perianal adenomas are common non-cancerous tumors of the sebaceous (skin oil) glands around the anus. They are most often found in un-neutered male dogs, although they can occasionally be seen on females that have not been spayed. Perianal adenomas are most commonly found in Cocker spaniels, Siberian huskies, and Samoyeds.

Perianal adenomas are not painful to your dog unless they become infected when they burst.

7. Skin Tags

Aging people and aging dogs can develop skin tags, which are also known as acrochordons.

These harmless growths extend out from the surface of the skin on a stalk. Also, like people, dogs may have a single skin tag or even dozens of skin tags on the chest, back, face, and legs. 

Skin tags are more common on dogs that have diabetes. They can become itchy and bleed. When this happens, they need to be removed. They won't become cancerous.

8. Mast Cell Tumors

Mast cells are immune system cells that release histamine to trigger allergic reactions. In healthy dogs, mast cells never accumulate in massive numbers. But some breeds, including beagles, boxers, Boston Terriers, Labrador Retrievers, and schnauzers, are prone to tumors consisting of cancerous mast cells growing just beneath the skin. They are most common in dogs over eight years old.

Mast cell tumors may be small and squishy, or large and ulcerated. Only your vet can provide diagnostic tests or rule out the possibility of this type of skin cancer.

9. Squamous Cell Carcinomas

Like squamous cell carcinomas in people, squamous cell carcinomas in dogs appear on skin that has been exposed to years of sunlight, or in the mouth or on nail beds. You are most likely to find squamous cell carcinomas on your dog in patches of skin that have less pigment or fur. Squamous cell carcinomas usually appear between the ages of eight and 10.

Squamous cell carcinomas won't metastasize to the rest of the body, but they can cause local tissue damage and disfigurement if they are not treated. While they are slow growing, treatment should not be delayed.

10. Soft Tissue Sarcomas

Soft tissue sarcomas are invasive cancers of the connective tissues. They most often appear between the legs, on the chest, or in the abdominal wall. Because they originate in connective tissue and not on the surface of the skin, they are usually palpable in the muscles. Don't delay seeing the vet if you detect a tumor in your dog's muscles.

11. Melanomas

Melanomas are unchecked growths of pigment-producing cells of the skin. When they occur under a dog's fur on the back or chest, they are often benign, but they do have a possibility of being a malignant melanoma. When they occur in the mouth or on the legs, they may spread rapidly throughout your dog's body. Always treat the appearance of irregularly shaped patches of pigment on your dog's skin as a reason to seek urgent care from your veterinarian and to receive an accurate diagnosis.

The best thing to do when you find lumps and bumps under the skin of your dog is...

Here is the most important rule for dealing with lumps, bumps, and lesions, on your dog's skin:

When you see something, do something!

Let your vet check out any lumps or bumps you detect on your dog. Chances are that it will be non-cancerous, but it takes a veterinary exam to know for sure.

Should your dog receive a definitive diagnosis of cancer, consider a change in diet. Canine Biologics offers and integrated approach to the best food for dogs with cancer. However, make sure your dog does not have a food allergy.

Our human-grade foodsupplements and wild-caught Alaskan salmon oil may help slow down the inflammatory processes that cause cancer. Canine Biologics specializes in food for dogs with cancer, and our products can help keep your dog as happy and active as possible. Animal wellbeing is just as important as human wellbeing!