Warning Signs of Cancer in Cats and Dogs

By isak, June 3, 2009

What are potential warning signs of cancer in dogs and cats?

It’s tragic that cancer in pets is increasing. According to the Pet Cancer Foundation, 60% of dogs over age six will be diagnosed with some form of cancer, and almost half the deaths of pets older than 10 years can be attributed to cancer. There are nearly 100 different types of animal cancer. The most common type in cats is leukemia, and the most common cancers for dogs are lymphoma and mammary gland cancer. With treatment advances, pets with cancer have a much better chance of survival than they did just a few years ago.

What are the warning signs? The Veterinary Cancer Group, a cutting-edge veterinary oncology practice in Southern California, provides a list of potential signs of cancer — which is not meant to give you a panic attack, but prompt you to make an appointment with your veterinarian if you notice any of these symptoms in your dog or cat. Provided verbatim from their website, the symptoms are as follows:

  • Swollen lymph nodes: These “glands” are located all throughout the body but are most easily detected behind the jaw or behind the knee. When these lymph nodes are enlarged they can suggest a common form of cancer called lymphoma. A biopsy or cytology of these enlarged lymph nodes can aid in the diagnosis.
  • An enlarging or changing lump: Any lump on a pet that is rapidly growing or changing in texture or shape should have a biopsy-the removal of a small piece of tissue for microscopic examination. Lumps belong in biopsy jars, not on pets.
  • Abdominal distension: When the “stomach” or belly becomes rapidly enlarged, this may suggest a mass or tumor in the abdomen or it may indicate some bleeding that is occurring in this area. A radiograph (X-ray) or an ultrasound of the abdomen can be very useful.
  • Chronic weight loss: When a pet is losing weight and you have not put your pet on a diet, you should have your pet checked. This sign is not diagnostic for cancer, but can indicate that something is wrong. Many cancer patients have weight loss.
  • Chronic vomiting or diarrhea: Unexplained vomiting or diarrhea should prompt further investigation. Often tumors of the gastrointestinal tract can cause chronic vomiting and/or diarrhea. Radiographs, ultrasound examinations and endoscopy are useful diagnostic tools when this occurs.
  • Unexplained bleeding: Bleeding from the mouth, nose, penis, vagina or gums that is not due to trauma should be examined. Although bleeding disorders do occur in pets, they usually are discovered while pets are young. If unexplained bleeding starts when a pet is old, a thorough search should be undertaken.
  • Cough: A dry, non-productive cough in an older pet should prompt chest radiographs to be taken. This type of cough is the most common sign of lung cancer. Please remember there are many causes of cough in dogs and cats.
  • Lameness: Unexplained difficulty walking-or the favoring of one limb over another-especially in large or giant breed dogs is a very common sign of bone cancer. Radiographs of the affected area are useful for detecting cancer of the bone.
  • Straining to urinate: Straining to urinate and blood in the urine usually indicate a common urinary tract infection; if the straining and bleeding are not rapidly controlled with antibiotics or are recurrent, cancer of the bladder may be the underlying cause. Cystoscopy or other techniques that allow a veterinarian to take a biopsy of the bladder are useful and sometimes necessary to establish a definitive diagnosis in these cases.
  • Oral odor: Oral tumors do occur in pets and can cause a pet to change its food preference (i.e. from hard to soft foods) or cause a pet to change the manner in which it chews its food. Many times a foul odor can be detected in pets with oral tumors. A thorough oral examination with radiographs or CT scan, necessitating anesthesia, is often necessary to determine the cause of the problem.

In the unfortunate event your pet is diagnosed with cancer, take heart. There are several treatment options that should be discussed with your veterinarian. For Betsy Rosenfeld, palliative radiation was the best course for her dog Bella, who was diagnosed with bone cancer and passed away in March 2009.

“I chose palliative radiation so that Bella and I could enjoy as many fun days as possible,” explains Rosenfeld, who worked with Dr. Jerrod Lyons at Veterinary Cancer Group. “The other vets all wanted to try aggressive and expensive treatments which included amputating her front leg, but the cancer had already spread throughout her body by the time she was diagnosed. Even if we had done all of those treatments, I still would have had to put her down when I did, but instead of taking car rides and eating chicken McNuggets we would have been living at the vet hospital.”

reprinted in part from Paw Nation


  1. Shawna says:

    How do you get a people prescription at pharmacy if it is for your dog? I love this option ,but I would like to know how to do it.

    • isak says:

      Because it is a prescription med, you have to have your vet write or call-in the prescription. My vet will call a couple places of my choosing to get the best price. If it is a rather standard drug, you might be able to get it at Walmart for $4. If it is a drug that has to be “compounded” especially for your pet, then the cost will be more, so shop around.

  2. TJ says:

    My 11 year old English Bull Terrier had NONE of these signs but when I took her in due to what turned out to be spine & neck arthritis, the vet discovered a tumor in her lungs. They tried a needle biopsy ($500) but could not access the mass. I have now used ALL of my money that I was saving for my property taxes on her & I am in need of help to care for her. Does anyone know of somewhere I can get help to care for her? (I am a 100% disabled Senior on very limited income & not only devastated by her imminent loss but want her to be comfortable and not in pain. The Vet wants $250/month for MEDS alone. I need to find her assistance. Thank you for any suggestions! “TJ”

    • isak says:

      You did not say where you are located. There may be some resources near you that your local rescue groups can tell you about, and there is a list on this website that may help.

      How does the vet know what meds to put her on if he was not able to access the mass?

      I don’t know what the meds are that the doctor is planning to prescribe, but sometimes getting them from a people pharmacy is cheaper. If they do not have to be specially made for your dog, you may be able to get them from a Walmart pharmacy. One of my pet prescriptions came from there and cost $4.

      Best wishes to you both.

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