Nov 01

Cancer in Pets

November is National Pet Cancer Awareness Month

What is cancer?

Cancer is a collection of related diseases. It can start anywhere in the body. Cancer cells divide without stopping and may invade into surrounding tissues. Normal cells typically form and divide when they’re needed by the body, then die when they’re damaged or old. Cancer cells disobey the rules: abnormal, damaged, and old cells gain abilities to grow and divide without stopping.

What’s so special about cancer cells?

Cancer cells are typically less specialized than other cells in the body, without any specific function. They ignore signals to stop cell division, and often have the ability to take advantage and influence the surrounding environment. Many cancers have the ability to hide from the immune system. Later in the disease course, cancers can gain the ability to invade into surrounding tissues, and may eventually spread to other sites. This is known as metastasis.

Are all cancers the same?

The brief answer is no. There are hundreds of different types of cancer and treatment and prognosis are based on the type of cancer, what organ systems are involved, and if the cancer has spread. Broadly, there are 3 major categories of cancer, although some tumor types do not fit precisely into each category:


  • Cancer of epithelial tissues
  • Arises from tissues that line body cavities or make up organs and glandular tissues


  • Cancer of connective tissue (mesenchymal)
  • Examples: bone, muscle, blood vessels

Round cell cancers (cancers involving immune cells)

  • Hematopoetic (“blood cancers”): ex. Lymphoma/leukemia
  • Histiocytic
  • Transmissible veneral tumors
  • Mast cell tumors
  • Plasma cell

How is cancer diagnosed in pets?

Cancer diagnosis may involve a number of tests to make the best treatment plan for each patient. A physical exam can be very useful to look for any new lumps or bumps, enlarged lymph nodes, or other physical abnormalities. Tissue sampling with a fine needle aspirate or biopsy may be recommended to determine an underlying tumor type to help guide treatment. Blood work is performed to determine the overall health of the pet, but cancer cells and markers are rarely seen on routine blood work. The stage of cancer may be based on the size of the primary tumor and/or how far the tumor has spread. Imaging of the chest and abdominal cavity are often recommended to screen for metastasis, prior to initiating treatment. This may be performed with chest x-rays, ultrasound, or CT scan.

After a diagnosis, what’s next?

Stay tuned for another blog post this month that focuses on cancer treatment options for pets.

Dr. Foskett is a Diplomate of the American College of Veterinary Internal Medicine (Oncology).  She graduated from Duke University, where she double-majored in French studies and Biology with a focus in marine biology.  She attended veterinary school at the University of Florida before completing a 1-year rotating internship at Friendship, followed by a 3-year medical oncology residency program with The Oncology Service. 

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