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Bumps & Lumps on Dogs and Cats

When people hear the word "lump," they often think of cancer. In reality, most lumps or bumps on dogs and cats you may find while petting or grooming your pet aren't serious, but it's still a good idea to have your veterinarian check them out anyway. Don't assume that a lump or bump will go away on its own, always be cautious and have your veterinarian examine any skin growth that is found on your pet.

Causes of bumps and lumps on dogs and cats

Skin growths, both benign and malignant, are fairly common in dogs and cats but that doesn’t necessarily mean your pet has a harmful form of cancer or another ailment. In fact, not all bumps and lumps you may feel on your pet are even tumors. Malignant tumors are cancerous and grow rapidly, potentially spreading to other organs and bones. However, benign tumors grow slowly and stay in the area they first developed, causing major issues only if they push up against another body part or organ. While tumors are new growths of tissue underneath the skin, many other lumps are caused by an accumulation of cells or fluid under the skin.

Common types of lumps on dogs and cats

If you find a lump or bump on your pet, don't panic. Most aren't life-threatening. The key is to make sure you take your pet to a veterinarian right away for an examination if you observe any signs or symptoms so the growth can be properly identified and appropriately treated. Read how to recognize various types of lumps, bumps and growths:

Types of skin growths on dogs and cats

  • 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 on dogs and cats 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 their head because of an itchy ear problem, they could potentially develop an ear hematoma.
  • 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.

Types of dog and cat tumors

  • 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.
  • 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.
  • 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.
  • Malignant skin tumors (skin cancer): 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.

What your veterinarian will do to treat a lump on your dog or cat

vet diagnosing bumps on dog

During a veterinary appointment, your vet can recognize some skin lumps in dogs immediately, such as lipomas and cysts. To identify other masses, 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 pet's growth is benign, your veterinarian will decide whether to remove it based on the location and size of the tumor. Malignant tumors, on the other hand, often require surgery, chemotherapy or radiation therapy.


In most cases, lumps on your pet's skin are more of an eyesore than an emergency, but leave that diagnosis up to your veterinarian. By regularly checking your dog or cat for bumps and lumps that were not previously there, you can help to catch any issues early on and ensure your pet is not experiencing any discomfort. Regularly established grooming routines will help you identify changes in your pet's skin and coat. A weekly brushing, daily petting and lots of love and attention are your pet's first defense.