Lumps and bumps are a fact of life for many pets, especially as they age—but that doesn’t make them any less concerning when you find one. Some are harmless and part of the normal wear and tear of a pet’s life. Others may be a sign of something more serious. Knowing how to tell the difference, and when to act, is key to protecting your pet’s health.

At Animal Hospital at Hillshore in Madison, WI, we regularly help pet owners evaluate new growths, determine what they are, and decide the best next step—whether that’s simply monitoring or moving forward with diagnostics or removal. This guide will help you understand what those mysterious lumps might be and when it’s time to schedule an exam.

Contact us if you’re concerned about a new lump—we’re here to help.

What’s That Lump? Understanding the Most Common Types

Not all lumps are created equal. Many are benign and completely manageable. Others can indicate infection, inflammation, or cancer. Being familiar with the most common types can help you feel more confident when something unfamiliar shows up.

One of the most frequently seen lumps in older pets—especially dogs—is a lipoma. These are soft, fatty growths that tend to be slow-growing, non-painful, and located just under the skin. Lipomas are usually harmless, though they may need removal if they begin interfering with movement or grow too large.

Then there are cysts—fluid-filled sacs that can appear suddenly and sometimes rupture. While generally benign, they can become irritated or infected, especially if your pet chews or scratches at them.

Abscesses, on the other hand, are a different story. These are painful, pus-filled swellings often caused by bites, scratches, or other wounds that become infected. They tend to be warm, red, and sensitive to the touch and usually require drainage and antibiotics.

Warts, or viral papillomas, are often seen in younger dogs and typically look like small cauliflower-like growths. They usually resolve on their own, but can multiply or become irritated.

Another common and completely normal lump: lymph nodes. These are small, bean-shaped structures found under the jaw, behind the knees, and elsewhere. When they become enlarged, it could be a sign of infection or something more serious, like lymphoma, so it’s worth noting changes in size or firmness.

More concerning growths include mast cell tumors, which are one of the most common skin cancers in dogs. These can look like almost anything—from a small pimple to a large, ulcerated mass—and may change size or shape quickly. Because mast cells release histamine, these tumors often become inflamed or itchy.

Soft tissue sarcomas are another category of cancerous growths that develop in connective tissue. These tumors may appear benign at first—firm, slow-growing, and painless—but they can be invasive below the surface.

Lastly, not all lumps are tumors. Sometimes, your pet might develop small inflammatory nodules or bug bites that look alarming but resolve within a few days. These can appear suddenly, especially during warm months, and are often itchy or red.

Because it’s difficult to determine what a lump is just by looking at it, a veterinary evaluation is always the safest course of action.

When Is a Lump an Emergency?

Some lumps warrant a closer look sooner rather than later. If a lump grows rapidly, becomes painful, bleeds, or is accompanied by symptoms like lethargy, appetite loss, or fever, it’s time to call your vet. A lump in combination with systemic symptoms could indicate infection or cancer and should be addressed quickly.

Other red flags include:

  • Changes in size, shape, or texture over a short period
  • Lumps that appear suddenly and are firm or fixed in place
  • Any lump that causes your pet discomfort or interferes with movement

Not sure whether to be concerned? Here’s a helpful resource outlining signs that a lump may be more serious.

How We Diagnose Lumps at Hillshore

When you bring your pet in with a new lump, we start with a thorough physical exam, followed by diagnostics if needed. One of the most common tools we use is fine needle aspiration (FNA)—a quick, minimally invasive test that allows us to collect cells from the lump for evaluation.

If the results are unclear or concerning, we may recommend imaging such as X-rays or ultrasound to check the extent of the mass and whether it’s affecting nearby tissue. In some cases, advanced imaging like CT or MRI may be necessary—particularly for internal or complex growths. For deep or ambiguous lumps, a biopsy can provide a definitive diagnosis.

Treatment Options: What Happens Next?

If the lump is benign and not causing issues, we may recommend monitoring it with regular measurements and check-ups. Some lumps can remain stable for years without intervention.

If the lump is painful, infected, or cancerous—or simply growing in a problematic location—surgical removal is often the best course of action. Post-surgical recovery typically includes rest, monitoring for signs of infection, and follow-up visits to check healing and, in some cases, discuss additional treatment.

Preventing Problems Before They Start

You can’t always prevent lumps, but early detection makes a big difference. Make a habit of running your hands over your pet regularly—especially during grooming or play. If you find something new, don’t wait to see what happens. Most issues are more treatable when caught early.

Routine wellness exams are another powerful tool. Your vet can track changes over time and recommend when something should be investigated further. Here’s how to do a simple home exam between visits.

Keeping your pet at a healthy weight, preventing injuries, and managing chronic health conditions can also help reduce risks for certain types of lumps and infections.

Your Partner in Peace of Mind

Finding a lump on your pet can be unsettling—but you don’t have to navigate it alone. At Animal Hospital at Hillshore, we’re here to help you understand what you’re seeing, provide clear next steps, and deliver the highest level of care, from diagnostics to surgery and beyond.

Contact us if you’ve noticed a new lump, or if your pet is showing any signs of illness. We’re ready to help you get answers—and peace of mind.