Critter Culture
10 Signs of Cancer in Pets

10 Signs of Cancer in Pets

Critter Culture Staff



We never want to think about our beloved fur babies being sick or having a disease, but we know it can happen. Recognizing the signs of cancer in pets is key to catching the illness early on and giving your furry family member the highest chance of survival. Some symptoms are more likely to indicate minor injuries, infections, or treatable diseases, but it's always best to be sure and check with your vet.


Swollen lymph nodes

A number of different cancers can cause lymph nodes to swell, including lymphoma, which is a common malignant cancer. Lymphoma can affect cats and dogs of all ages and breeds. The dogs that most commonly get lymphoma are golden retrievers and boxers.

Most people notice swollen areas on their pet’s neck, knee, or armpit that cause them to call the vet and might lead to a cancer diagnosis.

Girl is holding a Beagle puppy in her arms. Dog in the hospital has a little mistress on her knees Aleksandr Zyablitskiy/ Getty Images


Non-healing wounds

Mast cell tumors are aggressive cancerous growths that often show up as skin lesions that don't go away. This type of cancer impacts immune cells, known as mast cells, involved in allergic and inflammatory reactions. These cells are present throughout the animal’s body, but the tumors tend to concentrate in the vessels near the mouth and nose.

Mast cell tumors are most common in older purebred dogs, and most often affect boxers, Boston terriers, bulldogs, and schnauzers.

cat with broken leg pyotr021/ Getty Images


Abnormal odors

If you catch a whiff of unusual, unpleasant smells coming from your pet’s mouth, ears, or other areas of the body, it could be a sign of cancer.

You may be saying, "But my dog’s breath stinks all the time!" It's true, but if you notice their breath is especially rank these days, it could be a sign that cancer cells are growing along the lining of the mouth or nose. Anal tumors can also produce an unusual odor that comes from the dog’s rear end.

Man complaining about dog smell. ajr_images/ Getty Images


Sudden weakness or collapsing

Pets can become weak from a wide range of factors, but when they suddenly collapse, it’s a different story. Collapsing due to hemorrhage is sometimes a symptom of cancer of the cells lining the blood vessels, a condition called hemangiosarcoma. This fast-spreading cancer typically develops in the heart, skin, spleen, and liver. It can also occur in the retroperitoneal space where the kidneys and adrenal glands are situated.

Worried woman taking care of weakening old dog at home. Poor animal suffer from stomach ache need medical treatment in vet clinic. Dima Berlin/ Getty Images


Extreme Fatigue

While it’s true that Fido and felines love their nap time, if your fur baby is unusually tired, it could be cause for concern. This is especially true if your typically active pet no longer has an interest in playing, going outside, or other favorite activities.

Pets with cancer may also sleep longer than usual during the day, and they're sometimes too tired to eat.

Lazy British Short Hair cat sleeping on a couch in a flat in Edinburgh, Scotland, with her face squashed as she is fully relaxed Kseniya Ovchinnikova/ Getty Images


Unusual discharge

Heavy bleeding, diarrhea, throwing up, and other forms of bodily discharge can indicate a serious health concern with your cat or dog. If the pet also has a bloated stomach, it could be a sign of cancer. So give your vet a call to schedule a check-up and possible biopsy.

This was my dog Cali's last day before we had to put her to sleep. She was a great Golden Retriever! stonena7/ Getty Images


Coughing or difficulty breathing

Coughing is not a natural thing for animals to do. Though many issues can cause this symptom, coughing is also an indicator of cancer in the respiratory airways or lungs. If the cough is persistent and it sometimes comes with blood, check in with your vet to make sure it's not a sign of a bigger problem.

Lovely young mother and daughter, spending time at home with their French bulldog puppies. FluxFactory/ Getty Images


Diarrhea or vomiting

Vomiting and diarrhea that don’t stop after a couple of days or get better with treatment should be investigated further. Digestive tract cancer and other medical issues can lead to long-term vomiting and diarrhea.

You should seek immediate veterinary care if you ever notice blood in your pet’s stool or vomit. Although there are other, less serious reasons for it, this is a common sign of stomach and colon cancer.

Calico cat face tongue funny humor on carpet inside indoor house home with hairball vomit stain and woman owner cleaning rubbing paper towel on floor krblokhin/ Getty Images


Lameness or evidence of pain

Limping, not wanting to move, hunched posture, and other signs of pain could also be signs of cancer. As sad as it is, our pets can’t tell us they’re hurting, but they can show us. If your usually cuddly kitty is suddenly hiding from you or hissing when you pick them up, or your active pooch no longer wants to run outside, check them for signs of injury.

If you don’t notice any, but they continue the strange behavior, bone cancer is one possible reason.

owner petting his dog, while he is sleeping or resting with closed eyes damedeeso/ Getty Images


Unexplained lumps and bumps

Several types of cancer can cause lumps or bumps on your animal’s body. Mammary gland tumors, for instance, primarily occur in female dogs that aren’t spayed or who have been spayed after they turned two. Squamous cell carcinoma is the most common form of canine skin cancer and can also cause this sign. A dog’s head, lower legs, rear, and abdomen are the places where these tumors usually appear as raised, wart-like patches or lumps.

As dogs age, they can develop lumpy masses under the skin known as lipomas. The good news is these growths are benign. It’s important to get any masses evaluated by your vet to make sure they're harmless and start a course of treatment immediately if they are not.

Dog paw and human hand are doing handshake sanjagrujic/ Getty Images


What Is Cushing's Disease in Dogs?

What Is Cushing's Disease in Dogs?

Get your paws on the latest animal news and information