Bumps & lumps on dogs: causes, treatment options and more

Your pup is your best friend — so when you notice a new lump or bump on your dog’s skin (or elsewhere), it’s natural to feel worried. Try not to jump to conclusions too quickly, though: there’s always a chance that a growth is harmless. To learn more, Dr. Aliya McCullough, Fetch’s Chief Veterinary Officer and Director of Veterinary Affairs, walked us through the different types of lumps and bumps on dogs and what they mean.

What causes sudden lumps and bumps under dogs’ skin?

If you find a new lump on your dog, the first thing you should do is check in with your veterinarian. Some common causes of lumps and bumps on dogs are: 

• Inflammation or swelling that’s usually in response to an insect bite or bacteria
• An abscess, or a painful accumulation of pus caused by bacteria
• Allergic reactions that look like hives
• Scar tissue that appears after a reaction to a vaccination
• Cancerous growths
• Cyst (AKA a formation of fluid or cell debris)
• Cuterebra or warble flies (bugs that typically burrow into rodents’ skin, but can attach to dogs if they’re exposed)

If the lump is accompanied by signs of sickness, it could mean your dog is experiencing an internal illness, like tumors, swollen lymph nodes or thyroid cancer. Symptoms of an internal illness may include: 

• Vomiting
• Diarrhea 
• Lack of appetite
• Chronic thirst 
• Going to the bathroom often
  

Types of lumps and bumps and where they appear on dogs’ bodies

A lump can often be identified by where it develops on your dog’s body — here are some examples: 

• Histiocytomas are small growths found on dogs’ heads, ears and legs. They’re typically common in younger dogs and usually go away on their own. 
• Lipomas, aka fatty tumors, commonly form on dogs’ chest, belly or legs.
• Sebaceous adenoma resemble warts and are found on older dogs’ legs or torso.

Papillomas are contagious bumps (similar to warts) that develop on top of the skin around dogs’ mouths and lips.

When to call the vet about your dog’s lump or bump

No matter the lump, it’s always a smart move to contact your vet. Sometimes lumps can appear on dogs overnight — if they don’t seem to bother your pet, you can monitor the growth at home until your next vet visit. But, if your dog starts licking or scratching the bump, or it changes in appearance, contact your vet as soon as possible. If the lump has been around for a while and doesn’t seem to bother your dog or change, keep an eye on the growth and check in with your vet at the next appointment.

If the growth does start to change, there are some key differences you should watch out for:

• Black or purple coloring
• Open sores
• Pink spots or bruising around the lump
• Hardening texture 
• Growth
• Discomfort

Treatment options for dog lumps and bumps

You should always get your pup’s lumps tested to be sure they’re not spreading, limiting your dog’s movement or about to rupture. Your vet will know the best plan of action. Some common tests include:

• Fine-needle aspiration (FNA): A needle will extract a sample of cells from the growth for testing.
• Biopsy: A portion or the whole lump will be removed and sent to a lab for review. 

How your vet treats a mass depends on if it’s cancerous or noncancerous. Some masses heal on their own, while others need to be surgically removed or undergo chemotherapy or radiation.

How can I tell if a lump on my dog is cancerous?

To determine whether your dog’s lump is cancerous, you’ll need to head to the vet for a checkup. Depending on the results, your veterinarian will work with your dog to determine the next steps or might refer you to an oncologist. Here’s a bit more about cancerous tumors in dogs that can be felt or seen by the naked eye:

• Mast cell tumors are cancerous and made up of a type of white blood cell also known as mast cells. They often form as a nodule on or underneath the skin with a hairless or ulcerated surface, but they can also affect the organs.
• Mammary tumors can be benign or malignant and arise from the cells that make up the mammary glands. Malignant mammary tumors are usually firm and either within or next to a nipple.

It's impossible to predict when your dog will develop a new lump or bump, which is why we recommend enrolling in a dog insurance plan with comprehensive coverage early. That way, you'll have peace of mind knowing that you can focus on your pet's treatment plan without stressing about vet bills.