All Things Dog

Cancer in Older Dogs

While cancer can occur in dogs of any age, it's more prevalent as a dog gets older. Cancer is also the leading cause of death in senior dogs, and can appear in almost any organ. It’s important to watch your dog closely and check with your veterinarian about your dog’s health.

Some of the more common forms of cancer in older dogs include:

  • Osteosarcoma—A bone cancer that is primarily seen in large breed dogs
  • Hemangiosarcoma—Stems from blood vessels and often affects the liver or heart
  • Lymphoma—Cancer of lymph nodes and cells
  • Squamous cell carcinoma—Occurs in the mouth and on the skin, often around the head
  • Mammary tumors (breast cancer) —Usually found in unspayed female dogs
  • Prostate cancer—More likely to be found in male dogs that have not been neutered
  • Unfortunately, there are no specific blood tests for these cancers, so diagnosis can be difficult in the early stages. However, by keeping a close look for any changes in your dog's regular habits and by feeling for any lumps and bumps on a regular basis, you may be able to catch cancer while it's still treatable.

    What to watch for

  • Sudden, unexplained weight loss
  • A sore that does not heal (skin cancers sometimes appear as raw, bleeding, or scabby areas)
  • Bleeding from the mouth, ears, or nose could indicate a tumor
  • Drooling or difficulty swallowing (could indicate a throat tumor)
  • Nagging cough, hoarseness, excessive panting, and tiring easily are indications of heart and lung cancer
  • Diarrhea or constipation, difficulty urinating or defecating, or the presence of blood or mucous in the stool or urine
  • A bloated or distended abdomen
  • If you notice any of these changes in your dog, contact your veterinarian immediately.


    If your vet finds a tumor, a biopsy will typically be sent to a laboratory for analysis by a pathologist. This will help determine the type of cancer and whether or not it's malignant. Many times it’s possible to simply remove the tumor, as in the case of most skin tumors. Removal of heart and lung tumors is much more difficult. In those cases, chemotherapy and radiation therapy may be options to consider.

    Bear in mind that not all tumors are cancerous. Lipomas (fatty tumors), warts, perianal adenomas, and histiocytomas are seldom dangerous and removal is usually a straight-forward procedure.

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