How to Check Your Dog or Cat for Lumps

Written by Small Door's medical experts

It's not uncommon to notice a bump or lump on your pet's skin. Perhaps you feel something abnormal while petting your dog or cat, or spot an unusual swelling while cuddling up. While not all bumps are concerning, as a pet parent, you’ll want to monitor your pet for skin changes. This can help you spot a potential problem before it becomes severe. You can check your dog or cat for lumps while grooming them, bathing them, or whenever you can make time to inspect their whole body with your eyes and fingers.

In this article:

What are lumps on dogs and cats?

The common lumps found on dogs and cats vary widely in appearance and severity. They can be small or large, firm or soft, red or discolored, oozing or closed. Numerous causes could be responsible for the eruption of a new lump, from acne, mosquito bites, or lipomas (benign masses of fat cells) to infections or cancers. Vaccinations are another potential cause, as pets may develop a new bump at the injection site shortly after receiving a vaccine. Not all lumps or bumps are cause for concern, but the only way to know for sure is having them checked out by a veterinarian. 

Some bumps may be called tumors, but they are not necessarily cancer. A tumor describes when cells grow abnormally and form a mass. Tumors can be malignant (cancerous) or benign (not cancerous). Because benign tumors are not cancer, their cells do not spread and invade other tissues, but they can grow large over time and cause pain, discomfort, and other problems. Malignant tumors are cancerous cells that can invade nearby tissues or organs and eventually may travel throughout the body and cause widespread disease. 

Your veterinarian can help distinguish whether a tumor is cancerous or benign. This process may start with surgery to remove a tissue sample from the mass (biopsy) or a needle sample, which involves extracting a small amount of cells and fluid from the tumor with a needle. Then, the tumor sample will be studied under a microscope to look for cancer cells. If a needle sample is used, the microscopic evaluation is called cytology. As the Veterinary Information Network (VIN) reports, approximately two-thirds of tumors forming in the skin or muscle layers beneath the skin in dogs are benign, meaning that one-third are malignant. However, tumors are more likely to be malignant in cats – about two-thirds are malignant, and one-third are benign. Sometimes, the location of the tumor will provide clues as to whether it is benign or malignant.

Why should you check your dog or cat for lumps?

Performing skin checks on your dog or cat is a preventive measure. In many cases, lumps and bumps are not incredibly worrying. You may bring your pet to the veterinary practice only to discover that the swelling you noticed is merely a harmless wart. Still, if it does turn out to be harmful, early detection and diagnosis can be lifesaving.

Paying attention to your pet's skin and contacting a veterinarian when you notice something abnormal helps ensure that if there is a problem, it can be diagnosed and treated before there are more serious effects from more advanced disease. Even non-cancerous bumps and sores are sometimes dangerous and require prompt treatment, including certain infections, insect bites, and allergic reactions. 

How often should you check your pet for lumps?

Your veterinarian will look for bumps and lumps during your pet's annual checkup. Yearly veterinary visits are generally recommended for your cat or dog unless health problems or age demand more routine care.

If you're not sure how often to inspect your pet between scheduled visits, you can ask your veterinarian for advice. They can tailor their recommendations to individual risk factors, such as the species, breed, age, and medical history. You can also plan according to your personal preferences and perform skin checks whenever it's convenient for you. Bathing or grooming your pets is often a good excuse to examine their skin.  

The most common types of lumps in dogs and cats

The common types of lumps afflicting dogs and cats are diverse and wide-ranging in severity, from harmless skin tags to life-threatening cancers. There are numerous types on both sides of the spectrum, and many others fall in the middle. 

Some of the most common non-cancerous skin growths in dogs include:

  • Lipomas

  • Histiocytomas

  • Perianal gland adenomas

  • Sebaceous gland adenomas

Some of the most common cancerous canine skin tumors are often:

In cats, skin lumps are most often:

  • Basal cell tumors (benign)

  • Mast cell tumors (benign or malignant)

  • Squamous cell carcinomas (malignant)

Below are some of the common lumps that can occur in dogs and cats:


Lipomas are benign growths made up of fat. These fatty tumors are usually located in the layer just below the skin and feel squishy, rubbery, and movable when touched. They commonly affect dogs, particularly Doberman pinschers, Labrador retrievers, and miniature schnauzers. Lipomas are rare in cats. Surgical removal of lipomas is generally unnecessary unless the growths are uncomfortable or you prefer to do so.  


Histiocytomas are benign growths that usually form as a single, hairless bump. They primarily affect younger dogs and often go away on their own. A similar type of growth called a fibrous histiocytoma can occur in cats. However, these lumps are malignant and require surgical removal.

Perianal gland tumors

Perianal gland tumors are benign growths that develop around the anus in dogs, typically those that are not spayed or neutered. These tumors do not occur in cats. They can form in clusters or as a singular tumor and may evolve into bleeding sores as they grow. Larger tumors can impede the affected dog's ability to poop and cause other problems. Treatment is usually necessary and may involve castration, surgery, or other options.

Sebaceous gland adenomas

Sebaceous gland adenomas commonly occur in dogs and cats, particularly in older age. These growths are benign and often appear in more than one location. They usually look like small, shiny bumps, but they can also be crusty and pus-filled.  

Mast cell tumors

Mast cell tumors are common in both cats and dogs. In cats, they are usually benign and most often appear alone as a hairless bump on top of the skin, although they sometimes develop underneath the skin and in clusters. Treatment may be optional. In dogs, mast cell tumors are malignant. They commonly affect dogs between the ages of 8 and 10 and show up on the legs, belly, or chest. They are highly variable in size, appearance, and growth rate. Canine mast cell tumors generally require treatment, although the options depend on your wishes and other factors. While these tumors can occur in any breed, Boxers, Bulldogs, and Boston terriers are the most susceptible. 

Soft tissue sarcomas (fibrosarcoma)

Soft tissue sarcomas are tumors that form within muscles, tendons, and other tissues. They sometimes bulge out from under the skin and can be seen or felt. These tumors affect dogs and cats and can be benign or malignant. Many are a type of soft tissue sarcoma called a fibrosarcoma. Fibrosarcomas should be treated, although tumors often grow back after surgery.

Squamous cell carcinomas

Squamous cell carcinomas are malignant tumors that commonly afflict dogs and cats. They form in the mouth or on the skin and usually look like raised sores. Older cats are prone to developing squamous cell carcinomas of the mouth, which may cause symptoms such as: 

  • Drooling

  • Bad breath

  • Decreased appetite

  • Oral discomfort  

When they develop on the skin, they tend to form in areas with high sun exposure, especially lighter areas like the belly. Malignant squamous cell carcinomas typically appear after the skin has already developed solar keratosis, which causes the skin to thicken and become discolored. Diagnosing these tumors early, before they can spread into nearby tissues, greatly increases the chances of treatment success.

Basal cell tumors/basal cell carcinomas

Basal cell tumors are benign lumps that commonly develop in dogs and cats, often in older age. They usually show up as a singular lump on the head, neck, or front legs, but can emerge anywhere. They may be ulcerated or hairless and can range in size. Larger or fluid-filled tumors may require surgery to remove. When basal cell tumors are malignant, they are called basal cell carcinomas. These tumors are more common in cats. They tend to show up as flat sores that multiply over time, spreading across the skin. 

Mammary carcinoma

Mammary carcinoma, or breast cancer, is common in dogs and cats. While male pets can develop this cancer, it primarily affects females. In cats, most mammary tumors are malignant – about 90% of them are, as VIN states. For dogs, about half are malignant. Cats usually have four sets of mammary glands, four on the right side of their belly and four on the left. Most commonly, feline mammary cancer occurs in the top glands (near the front legs) or the bottom glands (near the back legs). In dogs, the number of mammary glands may vary. In the absence of mammary carcinoma, these glands should feel soft to the touch when you press down lightly on the belly. Any firm lumps that develop around the mammary gland area could signify mammary carcinoma and warrant a trip to the veterinary practice. Malignant mammary tumors tend to spread quickly and should be diagnosed as soon as possible to increase the chances of treatment success.

How to know if a lump on your pet is concerning or not

There is no definitive rulebook to tell you whether a lump on your pet is harmless or dangerous. The similarities between various bumps can be misleading to pet owners. For example, cancerous growths called mast cell tumors and benign masses of fat called lipomas may look similar to the naked eye. However, your veterinarian can quickly tell the difference between these growths by examining a sample of cells collected through a biopsy or fine-needle aspiration. In some cases, a veterinarian's specialized knowledge enables them to identify a bump through visual examination alone.

Any unusual swelling is potentially problematic, but the best way to find out is to make an appointment with your veterinarian. It’s particularly important to consult a veterinarian if the mass is painful, growing rapidly, bleeding, oozing, or bruised. With their medical equipment and expertise, your veterinarian can determine whether a bump is worrisome or not and decide on a diagnosis.  

How to check your dog and cat for lumps

Checking your dog or cat for lumps is a relatively simple process involving your eyes and hands. It’s a good idea to first examine your dog or cat when they are perfectly healthy, noting any lumps or irregularities that your veterinarian has deemed normal. If you spot a concerning bump later, you can refer to this information as a point of comparison.

  • You can start a skin check by taking a step away from your pet and assessing their overall appearance, focusing on their skin/coat and body shape. Note any abnormalities, such as an area of bulging skin or broken fur. 

  • Next, you can approach your dog or cat and begin to pet them, feeling their coat. Ideally, their hair and skin should be smooth and unbroken. Take notice of any sores, lumps, bumps, or hairless patches. 

  • After you have lightly and thoroughly touched the entirety of your pet's body, you can focus on their underside or belly and slightly increase the pressure of your touch. Find your pets' ribs, place your fingertips just below them, and apply light pressure. 

  • Then you can slowly work your way down the rest of their abdomen and to their legs, gently pressing your hands as you go. Look for anything that feels abnormal, including lumps, masses, or bulges. The abdomen should be soft to the touch, not stiff or swollen. Pay attention to your pet's behavior as you gently press down on their belly – they should not show any signs of pain or unusual discomfort.

Examine your pet's full body for lumps during a grooming session

Grooming can provide a convenient window for examining your pet's body and checking for lumps. It is also good for your pet's skin, as it helps remove old fur and untangle knots. Matted hair can foster moisture near the skin and increase the chances of infections. Next time you groom your dog or cat, consider paying closer attention to their skin and checking for unusual spots, such as patchy fur, wounds, or bumps.  

Take a photo as a visual record

If you find a lump or bump on your dog or cat, it's a good idea to take a photo. This way, you will have a visual record to show the next time you bring your pet for a checkup. You may be able to send the photo to your veterinarian, who can decide whether the lump warrants an immediate evaluation. An image can also be a helpful point of reference if the problem changes or grows.  

Ask your vet to check out any new or changed lumps

After spotting a potentially concerning lump, you should contact your veterinarian or make an appointment to bring your pet into the veterinary practice for evaluation. It's difficult to know whether a new or changed bump is indicative of a serious problem, but the only way to find out is to consult a professional. 

How your vet diagnoses a lump on your pet

Diagnosing a lump at your veterinarian's practice may start similarly to an at-home skin check. Your veterinarian will look at the spot and may examine it with bare or gloved hands. They will likely ask you some questions, such as when you first noticed the bump. Based on your pet's medical history and a physical examination, your veterinarian will decide whether further testing is needed. If they suspect the lump may be problematic or don't know exactly what it is, they will utilize various diagnostic tools, such as:

  • Blood tests

  • Urine tests

  • Imaging scans 

  • Biopsies

  • Cytology 

Blood and urine tests can be helpful to check for infection or other conditions. Imaging tests, such as X-rays, ultrasounds, and magnetic resonance imaging (MRI), may be used to determine suspected cancer growth. These tools render images of the inside of the body and can reveal where cancer may be located.

A biopsy involves removing some cells or tissue from the bump and examining the sample under a microscope. Biopsies can be performed using a needle to remove cells (fine-needle aspiration) or with surgical tools to remove all or some of the mass (excisional or incisional biopsy). Microscopic analysis of the cells within the growth is often the only way to definitively distinguish between cancerous and non-cancerous lumps. If the sample is collected through fine-needle aspiration, a process called cytology will be used to microscopically examine the cells. 

What treatment might be required for a lump on your pet

There is enormous variety in how veterinarians treat different lumps. If your veterinarian determines that your pet's bump is not harmful, such as a wart or lipoma, treatment is usually unnecessary. Surgical removal may or may not be recommended for benign tumors, such as histiocytomas or sebaceous adenomas, depending on the circumstances and your preferences. 

The treatment options for malignant tumors will depend on several factors, namely:

  • The type of cancer

  • Where the cancer is located

  • Your pet's overall health

  • Your preferences

Surgically removing the tumor is often the primary option and the most cost-effective. Radiation therapy and chemotherapy may be recommended in some cases, usually in addition to surgery.

Summary of lumps on dogs and cats

Discovering a new lump on your pet is not an uncommon experience for pet owners, and the average bump is usually not a significant cause for concern. However, some growths are signs of potentially serious problems, including cancer. Remember that you know your dog or cat best as a pet owner and can notice potential problems before anyone else. Examining your pet between regularly scheduled visits to the vet can help reduce the risk of overlooking a new or changing lump that could be harmful. Whenever you notice something abnormal, it's always prudent to proceed with caution and consult your veterinarian. Once your veterinarian determines the cause of a bump through a physical exam and other diagnostic tests, they can offer treatment options if necessary. 

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