Cancer Warning Signs in Pets

Updated: 3/21/24

While the thought of your beloved pet developing cancer may be frightening, many types of the disease are treatable if caught early. Be on the lookout for these warning signs and contact your veterinarian if you see anything concerning.

bump of dog's head

Lumps and bumps

Never assume a skin mass is “just another fatty tumor.” Have each skin mass checked by your veterinarian and keep a body map of the lumps so you know when a new lump occurs. Skin masses in cats are more likely to be malignant than those in dogs.

Closeup of dog mouth

Abnormal odors

Serious bad breath is typically caused by periodontal disease or a tumor in the mouth. Bad smells can also indicate the presence of bacteria which can result from an infection or wound related to cancer.

Cat with discharge from eye

Abnormal discharge

Watch out for increased discharge from your pet’s eyes, nose, or ears. This could be a sign of a tumor or other serious illness.

Dog with wound on face

Non-healing wounds

If your pet has wounds or sores that are not healing on their own or with prescribed medications, this may indicate cancer.

Skinny dog

Weight loss

Since obesity is such a common problem in dogs and cats, many pet owners are thrilled when they notice their pet has lost weight. However, if you do not have your pet on a diet, your pet is not likely to lose weight. Be sure to have unexplained weight loss checked out by your veterinarian.

Cat not eating

Changes in appetite

Both an increase or decrease in appetite can be a signal of cancer in your dog or cat. Be sure to monitor whether your pet is eating more or less than usual.

Dog coughing

Coughing or difficulty breathing

Cancer can affect your pet’s breathing in several different ways. Any change in your pet’s normal breathing pattern or a reluctance to exercise should be discussed with your veterinarian.

Cat looking tired

Lethargy & depression

If your pet seems uninterested in daily activities, is sleeping all the time or doesn’t feel up to their daily walk or play session, this might be a sign of a serious illness, including cancer. A trip to the veterinarian for a nose-to-tail examination is in order.

dog lifting leg to urinate

Changes in bathroom habits

Excessive water drinking, blood in the urine, difficulty urinating or defecating, frequent diarrhea, or blood in the stool are all potential signs of cancer.

dog with cast on letg

Evidence of pain

Many older dogs limp because of painful arthritis, but dogs can also limp due to bone cancer. Limping dogs need to be examined by a veterinarian.


While not all types of cancer are preventable, check out our blog for some practical steps you can take to reduce your pet’s risk.

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About Oncology at AMC AMC’s Cancer Institute is a revolutionary medical center, created to provide integrative and comprehensive care for pets diagnosed with cancer. This innovative design enables our staff

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