Guide to Canine Cancer


" Canine cancer is the result of cell growth which is uncontrolled and that serves no purpose. Cancer in dos is also referred to as a neoplasia, tumor and malignancy. Any body tissue can develop cancer. Cancer either originates at a site, which is called primary cancer or spreads from another area, which is called secondary cancer. Cancer spreads in the body through the blood or the lymph system, with lymphomas being one of the most common cancers in dogs. Estimates indicate that as many as 1 in 3 dogs will develop lymphoma.

Once a cancer starts to spread it becomes increasingly more difficult to treat (called cancer that has metastasized). Treatment for specific types of cancer in dogs can be found by clicking on the links below for each specific type ."

Video on on Treating Dog Cancer and Tumors


Hearing that your dog has canine cancer does not mean the end of its life. Like cancer treatment in people, there are now many options for treating your pet. In general, treatments tend to be more effective and have fewer side effects. Cancer is seen in about 1,100 of every 100,000 dogs and is treated by a veterinary oncologist.

Cancer is often referred to as a tumor, which is any sort of lump of bump. Tumors that grow are called neoplasms. There are two types of tumors:

  • Benign: Tumors that grow slowly and don’t spread to other parts of the body are considered benign as they have not metastasized or spread. A benign tumor is treated with surgery.
  • Malignant: These tumors are the same as cancer and are also called carcinomas, sarcomas and lymphomas depending on where the cancer is on the body. As the cancer spreads from one part of the body to another, it can enter the lymph nodes or circulatory system. The spread is called metastasizing.

What is Canine Cancer?

In a normal dog cells are constantly dieing and being replaced. In a dog with cancer, something is wrong with the replacement cells (called mutant cells). These mutant cells reproduce quickly and form into large groupings. Since these cells are mutant, they cannot provide the same function as the healthy cells they replaced. If these cells or cancer grows, it eventually replaces healthy tissue and causes the dog to die.

Tumors on Dog Leg

Mast Cell Neoplasia on Legs of a Sharpei

High Risk Breeds for Cancer

  • Basset Hound – Trichoepithelioma

  • Kerry Blue Terrier – Pilomaticoma

  • Cocker Spaniel – Ceruminous Adenoma

  • English Cocker Spaniel – Anal sac gland carcinoma

  • Giant Schnauzer and Gordon Settler – Subungual squamous cell carcinoma

  • Vizsla and Miniature Schnauzer – melanocytoma

  • Shetland Sheepdog – liposarcoma

  • Boxer and Pug – Mast Cell Tumor

  • Cocker Spaniel – Cutaneous Plasmacytoma

  • Bernese Mountain Dog* - greatest incidence of cancer in a 20-year study of nearly 75,000 dogs

  • Golden Retriever*

  • Scottish Terrier* – Subungual malignant melanoma

  • Bouvier des Flandres*

  • Boxer*

  • Bullmastiff*

  • Irish Setter*

  • Airdale Terrier*

  • Gordon Setter*

* According to a study in the Journal of Veterinary Internal Medicine that reviewed causes of death for nearly 75,000 dogs from 1984 to 2004,  breeds where cancer is more common (in descending order, asterisk breeds only).


There are several early warning signs of

  • Unusual swelling that continues to grow
  • Sores that do not heal
  • Weight Loss
  • Loss of appetite
  • Offensive odor, especially from the mouth
  • Bleeding or discharge from any body opening
  • Reluctance to move or exercise, loss of stamina
  • Difficulty eating or swallowing
  • Loss of energy
  • Difficulty breathing, urinating or making a bowel movement
  • Sleeping more than usual
  • Persistent lameness or stiffness

Dog Cancer Symptoms Example

Akita pup with fibrosarcoma

Symptoms Requiring Emergency Treatment

  • Your dog has collapsed

  • Bleeding after receiving chemotherapy

  • Loss of appetite while undergoing treatment

Symptoms Requiring a Call or visit to your Veterinarian

  • Skin – Sores, bumps, lumps
  • Leg – Large breed with swelling or a limp
  • Seizure - In older dog that has a seizure (uncontrolled shaking) for the first time
  • Nose – blood coming from the nose
  • Mouth – Lump, bump or growth
  • Breast – lump or swelling

For more information visit our guide to .


Determining if your dog has cancer usually requires more than blood tests or x-rays. Your Veterinarian will need to take a sample of the area in question (a biopsy) and send it to a laboratory to test for the presence of cancer. Cancer cannot be diagnosed visually since an examination of individual cells is necessary. If cancer cells are found (called malignant), your entire dog will need to be examined since many types of cancer can spread.

Testing will help the veterinarian classify the stage of development the tumor is in.  Each stage is associated with a specific treatment protocol or plan and indicates a dog's prognosis (course and outcome of the disease).

Dog Cancer Diagnostic MRI

Advanced Diagnostic Tests Such as a MRI (shown) Are Used to Diagnose Cancer in Dogs

Tests for Canine Cancer

Even with the advanced canine cancer tests listed below, it is still possible to miss a small tumor.

  • Biopsy – The removal of a small sample (non-excisional) or an attempt to completely remove a cancerous mass (excisional). The biopsy is sent to a lab for analysis. A veterinarian may remove an entire lymph node to see if cancer has spread or if cancer of the lymph nodes exists.
  • Fine-needle Aspiration (FNA) – Like a biopsy, but instead of surgery, a needle is used to extract cancerous cells for testing.
  • Blood Tests (CBC) – There is no blood test for cancer. Changes in the composition of blood could indicate problems such as low red blood cells, high white blood cells or changes in kidney and liver function.  These test are called a chemistry profile and blood count.
  • X-Ray – An x-ray will detect tumors in the lungs, chest or bones.
  • Ultrasound – The best technique for detecting tumors in the abdomen. A biopsy would be needed to confirm any findings.
  • Endoscopy – A video camera on a thin tube that is inserted into the mouth or nose to look for tumors. Used to examine the colon, bronchi and stomach. 
  • Surgery – To examine any area in question.
  • CT/MRI Scans – Best technique for detecting tumors that are near bone are unable to be seen by X-rays. 
  • Urinalysis- to check urine components
  • Bone Marrow Aspirate - the removal and testing of bone marrow
  • Lymph Node Aspirate - the removal of lymph node fluid
  • Immunologic Studies - testing immune response

Tumor Node Metastasis Rating System

A veterinary oncologist will use a ratings system that defines the size and spread of a tumor.

  • Tumor Size or Extent (T=Tumor)
    • Tis: preinvasive tumor (in situ)
    • T0: no evidence of tumor
    • T1: tumor <5 cm in diameter but confined to primary site
    • T2: tumor >5 cm in diameter or ruptured tumor
    • T3: infiltrative tumor
      • a: no bone invasion
      • b: bone invasion
  • N = nodes
    • N0: no evidence of lymph node enlargement
    • N1: movable ipsilateral nodes enlarged
    • N2: movable contralateral/bilateral nodes enlarged
    • N3: fixed nodes
  • M = metastasis
    • M0: no metastasis
    • M1: metastasis detected


If a tumor has spread (metastasized) in most cases a cure is not possible.  In these cases the purpose of dog cancer treatment is to focus on maintaining a dog's quality  of life (this is called palliation). Palliation or palliative care seeks to minimize pain and reduce any functional difficulties such as urination and swallowing.

Tumors that have not spread (referred to as being localized) have the best prospects for being cured. Treatment usually involves some combination or single use of immunotherapy (improving the immune system), surgery, chemotherapy or radiation. Curative approaches are commonly used if the tumor can be controlled for one year or longer after the start of treatment.

For example, radiation can be used to shrink a tumor followed by surgical removal of any remaining cells.

Radiation Therapy is Used to Treat Cancers Such as Brain Tumors, Nasal Cavity Tumors, Thyroid Tumors, Soft Tissue Sarcoma and Mast Cell Tumors

Treatment approaches for canine cancer:


  • Cancers commonly treated with surgery include:
    • Mammary tumors (except inflammatory mammary cancer) - most prevalent tumor in female dogs.
    • Prostate tumors
    • Oropharyngeal tumors
    • Skin cancers
    • GI tumors
    • Lung tumors
    • Bone tumors

  • Surgery can have complications with risk increasing based on the age of the dog. Complications include incomplete healing, blood loss, wound infection and the formation of abscesses.  There is also a risk of death caused by the surgery itself.

Radiation therapy is used for many types of tumors.
  • Cancers treated with radiation:
    • Brain tumors
    • Small pituitary tumors (can be curative)
    • To extend the survival time for spinal lymphomas and intracranial tumors
    • Nasal cavity tumors
    • Mast cell tumors
    • Soft tissue sarcomas
    • Thyroid tumors
    • Downsides include the possibility that the radiation will not reach cells in the center of the tumor. The radiation may effect surrounding skin or the lining of the gastrointestinal tract. Can also cause blindness or organ malfunction.

Chemotherapy is used to treat systemic cancers as the sole agent (see list that follows). It is also given to patients that have successfully completed surgery and/or radiation as an additional therapy.  Chemotherapy can improve the effectiveness of radiation therapy while helping to slow down tumor growth.

When used in combination with surgery, chemotherapy can reduce tumor size before surgery. Other benefits include the ability to kill microscopic cells and to slow down tumor growth.

Canine cancers treated with chemotherapy include:
  • hematologic malignancies
  • metastatic carcinomas
  • Metastatic sarcomas
Problems with chemotherapy include toxicity, problems with the immune system and anemia. Symptoms can include vomiting, nausea, problems with wound healing and dog hair loss.


Hyperthermia is considered to be the most effective treatment approach when used in combination with chemotherapy or radiation.  It is used to treat tumors that are small (<1.0 cm) or malignant and superficial.

The limitations of hyperthermia canine cancer therapy includes that it can damage both normal and cancerous cells. It can also cause skin burns. Like other treatment methods, hyperthermia can be used in combination with radiation and chemotherapy.

With radiation, hyperthermia can double the response to therapy. It can improve survival teams by improving the rate of response to therapy. With chemotherapy the hyperthermia improves that performance of medications that work better at higher body temperatures. It may also protect normal cells against the toxicity of the chemotherapy agents. That said, other studies indicate that the combination of hyperthermia and chemotherapy might increase treatment toxicity.

PDT Canine Cancer Therapy

Photodynamic Therapy (PDT) is used in dogs with superficial, minimally invasive and localized tumors

Photodynamic Therapy (PDT)

Photodynamic therapy for canine cancer is used in a limited number of instances. It is primarily used in dogs that have local (limited to one area) and superficial tumors that are minimally invasive. This includes tumors that are on the lining of the urinary bladder, oral cavity and skin.

Limitations of this type of therapy includes the inability of light to deeply penetrate into the skin or tumor tissue. The dog patient must be kept in reduced lighting conditions for 4 to 6 weeks after treatment. Not all tumors react the same way to treatment.

Gene Therapy

There are four types of gene therapy available to treat dogs:
  • Drug resistance gene therapy
  • Tumor suppressor gene therapy
  • Genetic immunotherapy
  • Suicide gene therapy
Anti-Angiogenic Drugs

These medications work by cutting off the blood supply that "feeds" a tumor. These medications are in the early development stages.


Immunotherapy uses immune system processes to attack cancer cells. Types of cancer treated include:
  • Soft tissue sarcomas (includes hemangiosarcoma and fibrosarcoma)
  • Osteosarcoma
  • Mastocytoma
  • Melanoma
  • Lymphoma
There are several types of medications that alter the immune response.  This includes:
  • Growth factors
  • Antibody therapy
  • Adoptive cellular therapy
  • Monokines/Lymphokines
  • Nonspecific immmunomodulators
Alternative Therapies

There are several alternative therapies that can help to reduce pain and other symptoms such as nausea and vomiting.  These include:
  • Acupuncture:
    •  for pain relief any vomiting and nausea that are side effects of chemotherapy and other treatment protocols
  • Massage
    • In cases where the massage will not interfere with treatment
  • Herbal Remedies
    • An oncologist might recommend products like to strengthen the patient or to address any side effects. If a dog is undergoing chemotherapy or radiation, check with your veterinarian to ensure that products like these can be used.

If a therapy is not available, then some dogs can be enrolled in a testing trial at a veterinary college.  A list of universities that are conducing canine cancer trials can be found at the .

Nutrition and Diet

In cancer patients, nutrition plays a dual role. It is most important to keep a patient healthy and nourished (to avoid a condition called cancer cachexia, which refers to severe malnutrition in cancer patients). Secondly, it is believed by some that some nutrients can help to slow down or prevent cancer.  Other nutrients may be able to reduce the side effects of radiation and chemotherapy.

In general, a dog cancer diet includes an increase of protein and a decrease in carbohydrates (carbs or glucose might fuel cancer cells). Other nutrients such as some vegetables, fruits and supplements can have a positive effect.

The problem for dogs is when the cancer alters the metabolism. This tends to happen during the early stages of cancer and will decrease the dog's quality of life over the course of the disease.

See our guide to formulating canine cancer diets for details on all aspects of nutrition and .

Dog Cancer Treatment Podcast

Here is a helpful podcast on cancer treatment in pets from the American Veterinary Medical Association. The podcast features Dr. Erika Krick, assistant professor of oncology at the University of Pennsylvania School of Veterinary Medicine. The discussion reviews recent development in canine cancer treatment.

AVMA Podcast

Should You Treat a Dog with Cancer

Cancer therapy can require a big commitment from an owner including multiple trips to the veterinarian and related costs.  These are decisions that can only be made by a owner. 

There are five criteria that are used to measure quality of life and canine cancer care. Dogs that score near normal on each factor tend to have better treatment outcomes.

  1. elimination of bodily fluids
  2. level of activity and exercise
  3. weight and condition of the body
  4. appetite
  5. alertness and mental status
Other methods for measuring quality of life include the ability of a dog to engage in activities that he or she enjoys.  See our discussion on if you would like some help and support when exploring this difficult decision.

If you decide to not treat the cancer, the focusing on care using alternatives and conventional approaches (called palliative care) for keeping a dog free of pain may be the best approach.  For example, products natural remedies such as contain antioxidants which help to strengthen healthy cells and boost a dogs immune system.  Again, these types of approaches are considered to be supportive vs. a specific cure.

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Brochures on canine cancer:

Guide to dog cancer. What is cancer and the available treatment options.
Available in Ebook

Overview of the many causes of cancer in dogs and cats.
Available in Ebook


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