Updated October 25, 2021.
As your fingers weave their way through your dog’s soft fur, you suddenly feel something unusual. A new lump! It strikes fear in all pet owners. Naturally, our minds go to the worst-case scenario.
Thankfully, most of the lumps we find on our dogs are not malignant. It’s common for older dogs to develop lumps on various parts of the body. The problem is that there’s no clear way to determine whether the lump is cancerous just by looking at it.
Yes, they’re scary. However, it’s important to remember that lumps and bumps are not uncommon and many are not malignant.
This post is designed to help you understand the wide variety of lumps and bumps on dogs. Just remember that unusual lumps must be seen by a licensed veterinarian.
Common Skin Lumps Found on Dogs
The following list is designed to give you a better idea of the types of lumps found on dogs. This is not meant to diagnose your dog. There are certain descriptions of lumps on dogs, but many can look very much alike.
Your family veterinarian will be able to have a look and tell you whether they are concerned or not. Keep reading to find out more about how veterinarians identify lumps and what can be done to treat them.
Mast Cell Tumors (Mastocytoma)
These are common, malignant (cancerous) lumps found on the surface of a dog’s skin. They can also be found below the skin or within the skin (subcutaneous).
Mast cell tumors are considered a type of skin cancer in dogs. They’re typically red, raised, and firm to the touch. They may form a wound that doesn’t heal on its own.
These frequently diagnosed skin tumors can occur in multiples or can pop up over time. Depending on the location, mast cell tumors can be surgically removed. Aggressive tumors that have already spread (metastasize) to the organs may have a poor prognosis.
Essentially, the dog’s skin contains natural mast cells that are responsible for fighting parasitic infection, aid in repairing skin tissue, from new blood vessels, etc.
When those mast cells go awry, they become mast cell tumors. The tumors pretty much shut down the skin’s ability to do the things it is supposed to do.
Mast cell tumors will usually spread through the dog’s body, particularly to the spleen, living, and bone marrow.
Mast cell tumors don’t all look the same. Some have smooth pink lumps whereas others can have ulcerated or raw skin lesions. In some cases, they can also appear as soft lumps under the skin.
Soft lumps under the skin tend to be diagnosed as a fatty lipoma (fatty tumors). Watch to see if the lump changes in size or appearance. They are known as “great imitators” due to their variety.
These are considered benign (not cancerous) skin growths. They tend to occur in young dogs (less than a year).
Look for red, raised, hairless growths. They are described as “button like” and can be the size of a nickel or quarter. They tend to occur on the head or limbs.
Sebaceous Cysts (also known as epidermoid or epidermal inclusion cysts)
Sebaceous cysts are look like a large pimple. They cause swelling under the skin and are filled with oil secretions that have become blocked. Most sebaceous cysts are non-cancerous (benign).
They have a pimple-like appearance and you might even be able to see what looks like a clump of dark or cheesy substance inside. Never pinch or try to drain a sebaceous cyst. That will cause pain for your dog and can leave the skin vulnerable to infection.
Sebaceous cysts can occur anywhere on your dog. However, you’re more likely to find them on the head, neck, ears, and anus.
Sebaceous cysts that occur on the anus are known as perianal adenomas.
Fatty Tumors (Lipoma)
Fatty tumors (lipomas) are very common in dogs. You’ll find them just below the skin where they feel like a soft, moveable mass. They can develop anywhere on the dog, but they often occur on the stomach or chest.
This kind of tumor is usually found on middle-aged or older dogs. They are not considered cancerous.
These tumors can appear as small lumps under the dog’s skin. They may appear haired and are quite soft. You may be able to move them around a bit. Sometimes fatty tumors will have a different texture and may actually be a bit firmer.
Squamous Cell Carcinomas
This is a tumor of the skin cells. They usually appear as a single lesion in one location. However, there are other types of squamous cell carcinomas that might present as two or more lesions in many locations of the body.
You might notice one on your dog’s nail bed, paw pads, stomach, trunk, on the ears or nose.
These tumors are found in light-skinned areas. Their appearance can vary significantly. For instance, they could appear small, red and irritated or ulcerated. They could also have crust or plaque on them.
A fibroma is a non-cancerous tumor common to dogs and found on limbs or pressure points. These are also known as skin tags, cutaneous tag, polyps, or collagenous hematoma.
Skin tags can appear anywhere on the dog’s body. They are often seen around the head, neck, and chest. They tend to grow very slowly and all breeds are susceptible.
Skin tags have a fleshy appearance. They are soft, slightly raised, and have the same color as skin. Sometimes they appear to dangle from a stalk.
Soft Tissue Sarcomas
These are a group of malignant tumors. They develop in the connective tissue below the skin. Overall, they make up about 15% of all skin tumors in dogs. You will usually see these as a single tumor in middle-aged to older dogs.
These tumors are cancerous and can quickly become aggressive. It’s important to have your dog checked regularly for new lumps and bumps. Early detection is the best way to prevent cancer from spreading.
These skin growths can appear as a single, hard lump under the skin. Sometimes they will open and bleed which leaves them vulnerable to infection. These tumors can cause swelling in the air surrounding it. They are often painful.
Sebaceous adenomas are benign tumors of the oil gland cells. They are commonly known as old dog warts because of how they look. They commonly affect middle-aged to senior dogs. Breeds most susceptible include terriers, poodles, cocker spaniels, and miniature schnauzers.
These are single or multiple raised, hairless, white to pale skin masses. They may ooze an oily material. These masses can range in size from 1/4 inch to 1 inch in diameter. Expect to find these on the trunk, legs, feet, or face.
Warts are caused by a viral infection and are not cancerous. They are, however, highly contagious to other dogs.
Dog warts can appear in the mouth or around the nose and eyes. At first, they begin as a rough patch of skin. Later they may develop into a darker, lumpier tumor that looks a bit like cauliflower.
Hives (urticaria) is a skin condition caused by an allergic reaction. They can appear anywhere on the body and range in size. Typically, hives are very itchy.
Hives are raised, red skin welts. They can occur from allergic reactions to insect bites, bee sting, vaccinations, or as a side-effect to medications.
An abscess is a fluid-filled lump in the body. It happens when the body is trying to wall off an infection. When skin is broken or injured, bacteria can settle under the skin. The resulting infection is a pus-filled lump.
Red, raised, pus-filled lump.
How Lumps and Bumps are Diagnosed on Dogs
The first thing the doctor will do is a thorough physical exam. He/she will palpate the dog and feel around for other new lumps or bumps.
The following are some common tests performed to identify lumps and bumps in dogs:
Fine Needle Aspiration
After a thorough physical exam, the veterinarian may want to do a fine needle aspiration. This is a simple procedure performed by inserting a small needle into the tumor and withdrawing a small tissue sample.
This is performed by rubbing a slide over a lump that is discharging fluid. The same is stained and examined the same way it would be with a fine needle aspiration.
A biopsy is performed by removing a small piece of the lump for examination under a microscope.
Blood work may be ordered to determine the overall health of your dog.
Treating A Dog’s Lumps and Bumps
Treatment options vary depending on the type, size, and location of the lump. In some cases, no treatment is required. Other times, surgical removal may be suggested. Some options may include:
A lumpectomy is the surgical removal of a lump. If cancer is suspected, the incision may be large to make sure that all potential cancer cells are removed.
Benign lumps and bumps can be removed using extreme cold. Liquid nitrogen is used to remove superficial skin lumps.
If your dog has a cancerous tumor that can’t be treated through surgery, radiation therapy may be an option.
Chemotherapy can be used after surgery in combination with radiation therapy.
Again, I can’t stress enough how important it is to bring your dog to a licensed veterinarian if you spot any unusual lump or bump.
At the end of the day, trying to sort out whether that lump on your dog is something to worry about is a useless venture.
Don’t panic, but don’t wait on it either. I keep saying this over and over for good reason: Make an appointment with your veterinarian and get that mysterious lump looked at.
With any luck, it will be nothing to worry about. But if it is something, the chances of a good prognosis are much better if it’s caught early!
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