Most lumps or bumps you may find while petting or grooming your dog aren’t serious, but it’s still a good idea to have your veterinarian take a look. Don’t assume that a lump or bump will go away on its own. Here’s what you need to know:


Skin lumps, both benign and malignant, are fairly common in dogs and cats, as well as small animals. Benign tumors usually grow slowly and stay put. Malignant tumors, or cancer, often grow rapidly, and they may spread to other organs or bones. But not all lumps are tumors. What’s the difference? A tumor is a new growth of tissue underneath the skin, while many other lumps are caused by an accumulation of cells or fluid under the skin.

8 common types of lumps, bumps and growths

Abscesses: Painful lumps that may form because of localized infection from a bite, wound or foreign object. These pockets usually contain a large amount of pus and blood, and they can rupture.

Apocrine cysts: Firm masses beneath the skin caused by obstructed skin glands. These benign cysts sometimes rupture like a pimple, which often clears them up.

Hematomas: These occur when blood accumulates under the skin after trauma. This blood-filled swelling appears as a lump or bruise and is usually painful. A swollen earflap can indicate an abscess or hematoma. If your pet violently shakes his head because of an itchy ear problem, he could potentially develop an ear hematoma.

Histiocytomas: Benign growths that often affect young dogs. They’re usually small, firm and dome- or button-shaped and appear on the head, earflaps or legs. They often disappear without treatment.

Injection-site reactions: These occur when pets develop a knot under the skin after an injection is administered. These tender bumps usually fade in a few days or a couple of weeks.

Lipomas: Typically common in overweight pets, these are benign tumors consisting of soft, smooth clumps of fat cells that can grow very large. They’re found most often on the chest, abdomen and front legs.

Malignant skin tumors: These may appear as a noticeable enlargement of a lump, or as a sore that won’t heal. Early detection is important, so always ask your veterinarian to check out any bump you find on your pet. Mast cell tumors are the most common malignant skin tumors in dogs.

Sebaceous gland hyperplasia: These can occur when the glands that secrete sebum (the oily substance that lubricates the skin) grow rapidly. These benign tumors are raised and can be smooth or wart-like in appearance and are often found on the legs, torso or eyelids.

What your veterinarian will do

Your veterinarian can recognize some skin lumps immediately, such as lipomas and cysts. To identify other lumps, your veterinarian may use a fine needle to obtain a tissue sample and examine the cells under a microscope.

If your veterinarian suspects cancer, he or she may recommend a biopsy, which involves removing part of or all of the tumor and sending it to a pathologist for identification. Biopsies usually require sedation or anesthesia.

Treatment for large hematomas, ear hematomas or an abscess involves draining the pocket and administering oral antibiotics as needed.

If your dog’s growth is benign, your veterinarian will decide whether to remove it based on the location and size of the tumor. Malignant tumors, however, often require surgery, chemotherapy or radiation therapy.

In most cases, lumps on your dog’s skin are more of an eyesore than an emergency, but leave that diagnosis up to your veterinarian.

Regular grooming will help you identify changes in your dog’s skin and coat. A weekly brushing, daily petting and lots of love and attention are your dog’s first defense.

Concerned about a growth or lump under your dog’s skin? Find a veterinarian near you >