When a single word turns your world upside down, we’re here to help by offering you information and inspiration to guide you through this difficult time.

You may have come here because a beloved dog has received a diagnosis of cancer. Or perhaps you are interested in cancer prevention for your pet. Whatever the reason, our mission is to be a valuable resource for all your needs.

The information contained on this site is in no way intended to replace the advice of a veterinarian. Please consult with a veterinarian immediately if you notice any of the 10 early warning signs of cancer in your dog.

The 10 Early Warning Signs of Cancer

( From the American Veterinary Medical Association)


  • Abnormal swellings that persist or continue to grow
  • Sores that do not heal
  • Weight loss
  • Loss of appetite
  • Bleeding or discharge from any body opening
  • Offensive odor
  • Difficulty eating or swallowing
  • Hesitation to exercise or loss of stamina
  • Persistent lameness or stiffness
  • Difficulty breathing, urinating, or defecation

Dog cancer, like human cancer, is the uncontrolled growth of cells on or within the body. Although there are many types of cancer, they all start because of out-of-control growth of abnormal cells. Normal body cells grow, divide, and die in an orderly fashion. During the early years of a dog’s life, normal cells divide more rapidly until the dog becomes an adult. After that, cells in most parts of the body divide only to replace worn-out or dying cells and to repair injuries. Because cancer cells continue to grow and divide, they are different from normal cells. Instead of dying, they are able to ignore signals that normally tell cells to stop dividing or that begin a process known as programmed cell death, or apoptosis, which the body uses to get rid of unneeded cells. The cancer cells outlive normal cells and continue to form new abnormal cells.

Cancer is a genetic disease—that is, it is caused by changes to genes that control the way our cells function, especially how they grow and divide. Cancer cells develop because of damage to DNA, the substance is in every cell and directs all activities. Most of the time when DNA becomes damaged the body is able to repair it. In cancer cells, the damaged DNA is not repaired. Dogs can inherit damaged DNA, or a dog’s DNA can become damaged by exposure to something in the environment, like smoke, pesticides or other carcinogens.

Cancer can start almost anywhere in the body, which is made up of trillions of cells. Many cancers form solid tumors, which are masses of tissue. Cancers of the blood, such as leukemias, generally do not form solid tumors.

Cancerous tumors are malignant, which means they can spread into, or invade, nearby tissues. In addition, as these tumors grow, some cancer cells can break off and travel to distant places in the body through the blood or the lymph system and form new tumors far from the original tumor (metastasize). Regardless of where a cancer may spread, however, it is always named for the place it began.

Unlike malignant tumors, benign tumors do not spread into, or invade, nearby tissues and usually are not life threatening. Benign tumors can sometimes be quite large, however. When removed, they usually don’t grow back, whereas malignant tumors sometimes do.

Diagnosing Cancer

Diagnosing Canine Cancer

Cancerous cells may be running rampant through a dog’s blood or localized in a skin tumor. They may be hidden in abdominal masses or multiplying in lymph nodes. When cancer is suspected, the techniques used to provide a definitive diagnosis are specific to the type of cancer it is thought to be. The diagnostic tools discussed in the paragraph below represent the most commonly used methods. In many cases and if caught early enough, there are a number of treatment options for dogs diagnosed with cancer.

When a tumor or mass is found on your dog, the first step in the diagnostic process is often to take a sample by a fine needle aspirate and/or a surgical biopsy. The samples will be evaluated microscopically to determine if cancer cells are present. Other techniques include taking impression smears of surgical specimens or open lesions, staining and evaluating those samples and surgical removal and histopathological assessment of whole masses. If cancer is suspected, thoracic radiographs (chest x-rays) probably will be taken to assess whether the disease has metastasized (spread) to the lungs. Ultrasound and fluoroscopy are other diagnostic options. A complete blood count, serum chemistry panel and urinalysis can provide a veterinarian with additional important information.

Cancer Facts

Canine Cancer Facts

Unfortunately, dog cancer is common. It is the leading natural cause of death in dogs. Approximately 50% of all dogs (6 million cases diagnosed each year) will be affected by a cancer in their lifetimes, and one report shows that 50% of dogs over the age of 10 will die from cancer. Estimates indicate that cancer occurs at least as frequently in veterinary patients as in humans. According to the Texas A&M Veterinary School, dogs have 35 times as much skin cancer as do humans, 4 times as many breast tumors, 8 times as much bone cancer, and twice as high an incidence of leukemia

The most common forms of cancer in dogs are:
Breast • Skin • Bone • Connective Tissue • Oral • Lymphoma

Known and Suspected Carcinogens (cancer causing agents) Include:

  • herbicide
  • insecticides
  • second-hand smoke
  • radiation exposure
  • certain viruses
  • genes/improper breeding
  • over/unnecessary vaccinations
  • chemical additives and preservatives in food