Lumps and Bumps on Dogs: What Pet Parents Should Know

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

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.

Frequently Asked Questions

When should I take my dog to the vet for a lump or bump? Schedule a veterinary appointment as soon as you notice any new growth — don't wait to see if it disappears on its own. Seek same-day or emergency care if a lump grows rapidly, bleeds, oozes, appears ulcerated, or if your dog seems painful, lethargic or unwell alongside the growth. Early detection is one of the most important factors in successful treatment outcomes.

Are most lumps and bumps on dogs cancerous? No — the majority of lumps and bumps found on dogs are benign. Common non-cancerous growths include lipomas (soft fatty deposits), histiocytomas, apocrine cysts, hematomas and injection-site reactions. That said, only a veterinarian can tell the difference between a harmless growth and a malignant tumor, so every new lump deserves a professional evaluation.

What does a cancerous lump on a dog look like? There is no single appearance that reliably identifies a malignant tumor — which is exactly why a vet exam is essential. Warning signs that raise concern include a lump that grows quickly, has irregular edges, feels firmly attached to underlying tissue, won't heal if it's open, or changes color or texture over time. Mast cell tumors are the most common malignant skin tumors in dogs and can mimic the look of harmless bumps.

How does a vet diagnose what kind of lump my dog has? Your veterinarian may be able to identify certain growths — such as lipomas or cysts — by physical examination alone. For anything uncertain, a fine needle aspirate (FNA) is the typical first step: a small needle draws out cells that are examined under a microscope. If cancer is suspected, a biopsy — removing part or all of the mass for pathologist review — may be recommended and usually requires sedation or anesthesia.

Can I monitor a lump at home instead of visiting the vet? Home monitoring is never a substitute for a veterinary diagnosis, but your vet may advise you to watch a confirmed benign growth (such as a small lipoma) over time once it has been properly identified. A practical habit: photograph the lump next to a ruler every few weeks so you can track any change in size and share that record at your next appointment. Never self-diagnose or delay care based on how a lump looks or feels.

How can I find lumps and bumps on my dog early? Regular grooming is your first line of awareness. A weekly brushing session combined with daily hands-on petting lets you feel for new growths beneath the coat before they become visible. Run your hands slowly along your dog's chest, abdomen, legs, earflaps and head — the most common sites for lipomas, histiocytomas and other growths. Note anything new and bring it to your veterinarian's attention promptly.

Lumps & Bumps at a Glance: Benign vs. Concerning Signs

Use this quick-reference table to understand what you're feeling — then bring your dog to your veterinarian for a definitive diagnosis. No table replaces a professional exam.

Common lump types decoded | Lump Type | Benign or Malignant? | Typical Appearance | Most Common In | |---|---|---|---| | Lipoma | Benign | Soft, smooth, moveable fat deposit | Middle-aged to senior dogs; overweight dogs | | Histiocytoma | Benign | Small, firm, dome-shaped; often pink | Young dogs (under 3 years); head, earflaps, legs | | Sebaceous gland hyperplasia | Benign | Raised, smooth or wart-like; oily surface | Older dogs; legs, torso, eyelids | | Apocrine cyst | Benign | Firm mass under skin; may rupture like a pimple | Dogs and cats of any age | | Abscess | Non-tumor; infectious | Painful, fluid-filled; may rupture and drain pus or blood | Dogs and cats; often after a bite or wound | | Hematoma | Non-tumor; traumatic | Blood-filled swelling; bruised appearance; painful | Any dog or cat after trauma; ear hematomas common | | Injection-site reaction | Non-tumor; inflammatory | Small, tender knot at injection site; fades in days to weeks | Any recently vaccinated pet | | Mast cell tumor | Malignant (most common malignant skin tumor in dogs) | Variable — can mimic a benign lump; may change size | Dogs of any age or breed; Boxers and Bulldogs at higher risk | | Other malignant skin tumors | Malignant | Enlarging mass or non-healing sore | Senior dogs; early detection critical |

Bottom line: A soft, slow-growing, moveable lump in a middle-aged dog is often a lipoma — but only your veterinarian can confirm that with a physical exam or fine-needle aspirate. When in doubt, get it checked.

Frequently Asked Questions

Should I be worried about every lump I find on my dog? Not every lump signals a serious problem — many are benign growths like lipomas, cysts or histiocytomas. That said, you should never assume a lump will resolve on its own. Have your veterinarian evaluate any new skin growth so it can be properly identified and monitored. Early detection makes a meaningful difference when a lump does turn out to be malignant.

What is the most common malignant skin tumor in dogs? Mast cell tumors are the most common malignant skin tumors in dogs. They can look deceptively similar to benign lumps, which is why a veterinary exam — and often a fine-needle aspirate — is essential for any new or changing mass.

How does a veterinarian tell whether a lump is cancerous? Your veterinarian may be able to identify some growths, such as lipomas or cysts, on physical exam alone. For other masses, he or she will use a fine-needle aspirate to collect cells and examine them under a microscope. If cancer is suspected, a biopsy — which involves removing part or all of the tumor and sending it to a pathologist — may be recommended. Biopsies typically require sedation or anesthesia.

Can a lump on my dog go away on its own? Some can. Histiocytomas, for example, frequently disappear without treatment in young dogs, and small injection-site reactions typically fade within days to a couple of weeks. However, you should never wait and hope a lump resolves — always have your veterinarian examine it first so you know what you're dealing with.

How can I find lumps on my dog before they become a bigger concern? Regular grooming is your first line of awareness. A weekly brushing, daily petting and routine hands-on time help you notice changes in your dog's skin and coat early. Run your hands along your dog's entire body — including the chest, abdomen, legs and earflaps — and note any new growths. If you find something unfamiliar, contact your veterinarian promptly.

Are lumps more common in older dogs? Yes — certain benign growths like lipomas and sebaceous gland hyperplasia are more frequently seen in middle-aged to senior dogs, and the overall risk of malignant tumors increases with age. That makes routine wellness exams especially important as your dog gets older. Ask your veterinarian how often your dog should be seen based on his or her age and health history.

This article was created with assistance from AI tools and reviewed for accuracy by Petco's content team.