Canine Lumps and Bumps

Medical articles
beagle getting vet check up

Veterinary appointments for a new lump or bump are some of the most common non-wellness appointments scheduled for dogs. Because a growth on a dog can be so many different things, it is not usually a question that can be answered without a check-up. For the most part, a new lump or bump can be the result of an infection, a tumor (cancerous or noncancerous), an injury, or a normal part of the anatomy.


New bumps on a dog’s skin may be the result of an infection. Dogs can get pimples (also known as pustules) and scabs from a skin infection. Usually this is caused by bacteria invading a wound, or it can be allergy-related. Surprisingly, allergies are pretty common in dogs. Red, itchy skin may be seen, as well as crusty scabs, red or white bumps, and an oozy fluid on the skin’s surface. If the bump is the result of an infection under the skin, an abscess or pocket of infection may have formed. In this case, the area will be swollen, firm, painful, and may leak fluid with blood or pus in it.

To diagnose the issue, the veterinarian will look over the skin closely. He or she may take samples of any fluid on or under the skin or inside a pimple to either examine under a microscope or send off for bacterial growth (known as culturing). Treatment usually depends on the cause of the infection. Cleaning, flushing, and treating the infected area with topical medications (applied directly to the skin) as well as prescribing antibiotics is common. Anti-itch medications (e.g. steroids, anti-histamines) may also be prescribed.

Dog Tumors

The most common types of skin tumors (skin masses) seen in the dog are the mast cell tumor, adenoma (sometimes called moles), lipoma, fibrosarcoma, melanomahistiocytoma, and squamous cell carcinoma. Of these, mast cell tumor, fibrosarcoma, squamous cell carcinoma, and melanoma are cancerous, but the rest of these tumor types are benign (noncancerous). Papillomas, which are dog warts caused by a virus, and cysts, which are fluid-filled, benign masses just under the skin are also seen somewhat frequently in dogs and they are benign as well.

In some cases, the veterinarian will be able to look at and feel the tumor to determine how to get an accurate diagnosis; however, he or she usually won’t be able to tell what type of tumor it is by looking at it. Next, the veterinarian will aspirate some of the tumor cells from the mass with a needle and syringe, apply special stains, and look at these cells under the microscope. Some types of tumors are easily identified this way, such as mast cell tumors and lipomas. If an answer isn’t obvious, the veterinarian will likely want to biopsy the mass, by either surgically removing it entirely or removing a small piece of it. The tissue will be sent to a veterinary pathologist, with results likely returned in 1-2 weeks.

Further treatment will depend on what type of mass is present. Benign masses may not need any additional treatment. Cancerous masses may require more surgery or a visit to a veterinary oncologist.


Sometimes an injury can cause a new bump to form. If you have ever bumped your head, you know that sometimes a knot will form if you bump it hard enough. This can be caused by swelling from blood under the skin or thickened skin/underlying tissues from inflammation associated with the bump (e.g. a sprain). If blood forms under the skin, it can cause a pocket-like swelling (without pus) called a hematoma, or it will clot and form a bruise. The area may be red, swollen, and painful. If the injury happens on one of the dog’s legs, he or she may also limp.

The veterinarian will examine the area and determine whether x-rays or ultrasound are needed to get an idea of the severity of the injury. If a hematoma is suspected, the vet may aspirate the fluid for microscopic examination (similar to looking for cancer cells or signs of inflammation/infection). Some injuries will improve with rest and warm compresses. Pain medication may also be needed, but do not give your dog anything over the counter without discussing it with your veterinarian first. For severe injuries, surgery may be needed to fix the damage.

Normal Lumps and Bumps

Although it seems unlikely, it is not uncommon for pet owners to notice what appears to be a new lump, only to find out it is normal when they get to the vet. Common lumps and bumps found on a dog that are normal are discolored nipples (and yes, male dogs do have nipples), elbow calluses, large whiskers (especially under the chin), bony points that become more noticeable after weight loss, and excess areas of fat that become more noticeable after weight gain. That being said, any new lumps or bumps should be checked out by your veterinarian, even if they don’t seem to be bothering the pet. It also might be a good idea to look into getting dog health insurance just in case something may happen to your pet in the future. Hopefully the new spot is nothing to worry over, but as Ben Franklin once said, an ounce of prevention is worth a pound of cure.