Skin Cancer In Dogs: Types, Symptoms, & Treatment

Written by: Colleen Ferriman, DVM

August 30, 2022

So you’re petting your dog at the end of a long day, cuddling and watching your favorite show, and you find a new lump. Don’t panic! You are not alone. Most owners of senior pets (7+ years old) have found a lump on their dog. You’re probably (rightly) a little concerned, but it’s important to remember that not all masses are cancerous. In fact, 80% of skin masses in dogs are benign, and almost all can be cured with surgery1. To help ease your mind, let’s talk about lumps and what you need to know. 

yellow lab at the vet

I’ve Found a Mass on My Dog. Now What?

If you find a mass on your dog, first feel the same spot on the other side of the body. While it is possible for masses to appear in the same spot on both sides of the body, this is extremely unlikely. If you have a male dog, make sure you’re not mistaking their nipples for a mass! Male does have nipples on the bottom of their chest and belly, and usually come in pair.

Related Article: Do Male Dogs Have Nipples?

Once you determine that this is a lump that does not match the other side, make note of exactly where it is and how big it is. You can do this by taking a photo, writing a note so you remember, or using a marker (bright colors help) to make it easier to find again. This information will help you to find the lump when you go to the vet, and to keep track of how the lump is behaving until then. 

Do I Need to Go Straight to the Veterinarian or Can It Wait?

If your dog’s only symptom is a small lump that is not painful, draining, or open, then it’s best handled by your regular veterinarian, but is not a “same day” appointment issue. While lumps are not usually an emergency, the longer you leave the lump, the larger it will get, and therefore the harder it will be for your veterinarian to fix. (Note: parts of the body with less extra skin need to be treated when the lump is small. So don’t delay a visit to the vet when you find a lump on the face, legs, or tail.)

Pet owner and dachshund consulting with veterinarian

The general rule of thumb is that anything larger than a centimeter (about the size of a single pea) that has been present for more than 30 days, or is bothering your dog, should be sampled by your veterinarian to get a diagnosis. When in doubt, if you are concerned, schedule the appointment with your vet. 

Related Article: Why Are Pit Bulls Prone to Skin Problems?

What are Some Common Skin Cancers in Dogs? What Do They Typically Look Like?

There are, unfortunately, no shortage of different types of cancers that can affect your dog. Some of the most common include:

Hemangiosarcoma/Hemangioma: Red to purple masses on belly where skin is exposed, seriousness varies

Histiocytoma: Raised, often hairless mass that can spontaneously resolve without treatment

Mast Cell Tumor: Red raised mass that can change in size (grow and shrink) if irritated, common in smush-nose breeds, seriousness depends on grade

Melanoma: Black raised mass, most benign but if found near eyes, nose, mouth or genitals more likely to be malignant 

Papilloma: White finger-like wart often found on the lips and gums of young dogs, usually resolve with time

Squamous Cell Carcinoma: Belly where skin is exposed, or toes nail beds of black haired dogs, seriousness varies

Remember, if you think your dog might have one of these lumps, get it examined by a qualified veterinarian. It is not possible to tell which type of mass it is without a sample. Cancer is capable of breaking all the rules, so get a diagnosis1-2.

Dog having its skin examined

How Can I Figure Out What Type of Mass It Is?

You and your vet have multiple options for diagnosing the mass on your pet:

Fine Needle Aspirate: Your vet will stick a needle in the lump, collect some cells, and examine them under a microscope. This can be done without sedation or anesthesia and is minimally invasive. The downside is sometimes you do not get a conclusive diagnosis and cannot determine how aggressive the mass is (in medical lingo, the stage or grade). 

Incisional Biopsy: This is when a small piece of the lump is cut out. This requires sedation or general anesthesia. This allows for diagnosis and can determine how aggressive the mass is, but does require a second procedure for definitive treatment. 

Excisional Biopsy: This is when the whole lump is cut out and sent off to determine diagnosis. While this avoids two procedures for diagnosis and treatment, there is a chance this method will leave behind cancerous cells.

Related Article: This Golden Retriever Puppy Was Given One Year To Live. Thirteen Years Later, He’s Cancer-Free And A Viral Sensation.

How Can I Make Sure Cancer Hasn’t Spread?

The best chance of cure for cancer is removing all of the cancer cells on the first surgery. So, before any invasive procedure, your vet will likely run your pup through some preliminary procedures. These help determine if any cancer has spread to other areas of your dog’s body.

Dog and owner consulting with vet about x-ray results

For skin cancers in particular, these screenings can be particularly helpful, because most skin cancers are benign. If your pup’s lump is benign and nothing is detected elsewhere in the body, that can simplify an otherwise very invasive surgery.

Some of these screening procedures include:

Baseline Bloodwork and Urine Test: This helps determine if there are any body systems that are stressed. This is also a common screening procedure before sedation or anesthesia. 

Lymph Node Aspirate: This is when a sample is taken from the lymph node that drains the area of concern (aka downstream from the mass) to see if the cancer has spread to lymph nodes. Note: sometimes these are inside the body and require ultrasound guidance.

Radiographs (X-Rays): Chest x-rays are used when cancer is suspected. Your vet will check to see if any masses are noted in the lungs, which would indicate the cancer has spread there. 

Ultrasound: An abdominal ultrasound is used when cancer is suspected to see if any masses are in the abdominal organs or abdominal lymph nodes. 

Hopefully your dog’s lump is benign and easy to diagnose! It’s unfortunate that skin cancer is a common issue in dogs, but luckily, it can typically be cured by surgery.

Happy man taking selfie with his dog in a park

And remember, early detection and prompt treatment make all the difference for curing skin cancer. If your pet has a lump larger than 1 cm that has been present for more than 30 days, is changing, or is bothering your dog, have them evaluated by your veterinarian. And cuddle your dog regularly so you notice any new lumps. Doctor’s orders. 

Colleen Ferriman, DVM, is a canine and feline health, wellness, and illness management advocate. She has a combined 10 years of experience in clinical medicine, education, and educational content development. Colleen graduated from Colorado State University as a Doctor of Veterinary Medicine, has worked as a general practitioner, and has contributed to the development of veterinary educational tools. She is also a member of the American Veterinary Medical Association and American Academy of Veterinary Pharmacology and Therapeutics.


1 Ettinger S.: The ABCs of Early Cancer Detection: Aspirates, Biopsies, and Cytology. Fetch DVM360 Kansas City 2021. 

2 Willcox J.L..: Mast Cell Tumors, Melanomas, & Beyond: Clinical Approach to Cutaneous Masses. Wild West Vet 2019. 

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Written by: Colleen Ferriman, DVM

August 30, 2022

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