Signs of Cancer in Dogs

“Cancer” is a scary word, and it can feel even scarier when your veterinarian tells you that your dog has it. Your mind might start racing with fear and uncertainty.

Fortunately, significant strides have been made in veterinary medicine to diagnose and treat cancer. In this article, we’ll describe the early warning signs of canine cancer and explain when to see a vet, as well as discuss what to expect during the diagnostic process and review treatment options for cancer in dogs.

How Common Is Cancer in Dogs?

Approximately 1 in 4 dogs will develop cancer during their lifetimes, and over half of dogs over age 10 will get cancer. With dogs now living well into their senior years, the likelihood of cancer increases.

Common types of cancer in dogs are listed below:

• Lymphoma: cancer of the lymphatic system
• Mast cell tumor: aggressive skin cancer
• Osteosarcoma: aggressive bone cancer
• Hemangiosarcoma: aggressive cancer in the blood vessels
• Melanoma: pigment cell tumor

Cancer in dogs often does not discriminate, but some breeds are more prone to developing certain cancers. For example, lymphoma is more common in Golden Retrievers, Boxers, Scottish Terriers, Rottweilers, and Bull Mastiffs. Large-breed dogs, such as German Shepherds and Great Danes, have a higher risk of developing osteosarcoma. Bernese Mountain Dogs and Boxers are prone to developing mast cell tumors.

Although cancer in dogs is not something you can prevent, detecting it early can improve treatment outcomes. Therefore, the earlier the diagnosis, the better.

Common Canine Cancer Signs

Signs and symptoms of cancer in dogs are frequently general and can be found with many other canine diseases. Your veterinarian will need to perform various diagnostic tests to rule out other conditions causing your dog’s symptoms before diagnosing cancer.

Here are eight common signs of cancer in dogs to watch for:

1. Lumps, bumps, discolored skin. If you feel or see a new lump or bump on your dog’s skin, it could be a sign of cancer. Not all bumps are cancerous, of course, but those that are rapidly growing are especially concerning. Take note of the bump’s size, shape, and evenness of its edges.
2. Unusual weight loss. When cancer attacks a dog’s body, it can steal vital nutrients, causing weight loss that has no readily apparent cause. Cancer can also cause a dog to feel unwell, leading to loss of appetite and subsequent weight loss.
3. Lethargy and weakness. Cancer robs dogs of their energy, leaving them feeling weak and tired.
4. Changes in bathroom habits. Depending on the cancer’s location, a dog’s bathroom habits may change. For example, bladder cancer can make urinating difficult and painful.
5. Coughing or difficulty breathing. Cancer in the lungs and airways of dogs can lead to respiratory issues, such as coughing or difficulty breathing.
6. Persistent lameness or limb swelling. Bone cancer can manifest as limb swelling that doesn’t resolve on its own, along with painful and persistent lameness.
7. Non-healing sores or bleeding. Non-healing sores indicate that something is affecting the immune system, preventing proper healing. Bleeding that doesn’t resolve could indicate cancer in the circulatory system.
8. Abdominal bloating or pain. Bloating and abdominal pain are non-specific and can be related to numerous conditions. Cancers in abdominal organs, such as the liver and spleen, can cause significant abdominal bloating and pain.

Be aware that dog cancer symptoms can appear gradually and easily be missed or attributed to aging. In addition, the symptoms may come and go. The only way to definitively know if your dog has cancer is to take them to your vet for a diagnostic workup.

Early Warning Signs vs. Advanced Symptoms

A small bump on the skin or a little less energy at playtime are subtle symptoms of cancer that you may not immediately recognize. As the cancer progresses, however, the signs become harder to miss. For example, significant and unintended weight loss, difficulty breathing, and visible pain are clear signals that something isn’t right and needs to be evaluated.

Although you may not know exactly what’s going on with your dog, trust your gut when it tells you that something is “off.” Let that hunch be your guide to schedule an appointment with your vet.

How Vets Diagnose Cancer in Dogs

Diagnosing cancer in dogs is a process that involves diagnostic testing to rule out other conditions that could be causing your dog’s symptoms.

The diagnostic process begins with a detailed history and physical exam. Your vet will ask you questions like these:

• What symptoms does your dog have?
• When did the symptoms start?
• Have any of your dog’s behaviors and habits changed?
• Is your dog in pain?

Your vet will then examine your dog’s body from head to toe, taking note of any abnormal findings that may point toward cancer. With the history and physical exam, your vet will formulate a list of possible diagnoses, including cancer.

Basic diagnostic testing includes blood work, urinalysis, and X-rays. Other diagnostic tools include ultrasound and sampling the mass itself, either through fine-needle aspiration (FNA) or biopsy. FNA involves removing a small ‘core’ of tissue from the mass with a long, thin needle.

Advanced tools include MRI and CT scans. These are not commonly used, but can be helpful in certain situations, such as when there is a suspicion of brain cancer.

After your vet has made the cancer diagnosis, they will categorize the cancer using the TNM classification, developed by the World Health Organization. TNM is described below.

• T: tumor size; is the tumor large enough to invade nearby organs?
• N: number of lymph nodes affected
• M: presence of metastasis (cancer spread in the body)

Remember that not all bumps are cancerous. For example, Labrador Retrievers often get lipomas, which are non-cancerous, fat-filled masses that grow under the skin.

Treatment Options for Dog Cancer

Treatment for canine cancer is typically multi-pronged, rather than relying solely on a single treatment approach. Here are the standard cancer treatment options for dogs:

• Chemotherapy: Chemotherapy may be used on its own to treat cancer, or it can be used to debulk the cancerous mass (make it smaller) so that it can be removed surgically. Although effective, chemotherapy can damage healthy cells as well as cancerous cells.
• Surgery: Surgery is ideal for cancers that have not metastasized and are located in areas that can be easily accessed. For particularly large masses, chemotherapy will be used first to make the tumor smaller and easier to remove.
• Radiation: Radiation is a targeted form of treatment that targets just the cancer, minimizing damage to the surrounding tissues. It is ideal for cancers that are located where they cannot be safely or fully removed surgically.
• Immunotherapy: Immunotherapy harnesses a dog’s own immune system to kill cancer cells.

There is no one-size-fits-all treatment that will work for all cancers, because cancers in dogs vary widely in size and aggressiveness. Thus, treatment depends on several factors:

• TNM classification
• Dog’s overall health
• Dog’s age

Dogs tend to tolerate cancer treatment relatively well and can enjoy a good quality of life during treatment. However, it is essential to monitor your dog’s response to treatment and notify your vet if your dog is showing improvement or worsening.

As with human cancers, not all dog cancers have a cure. Additionally, some cancers may be so advanced at the time of diagnosis that treatment is neither practical nor feasible. In these cases, pet parents may choose to forgo cancer treatment in favor of palliative care, which prioritizes comfort, compassion, and quality of life.

If your dog has cancer, make sure to discuss any treatment options with your vet, including those that are palliative. You and your vet can develop an ideal treatment plan for your dog.

When to See a Vet

Although the signs of cancer can be subtle, you know your dog well enough to know when something just isn’t right with them. If you’re wondering when to see your vet for dog cancer, schedule an appointment if your dog experiences unexplained weight loss, has sudden behavioral changes, or develops new lumps and bumps under their skin.

The earlier you take your dog to see the vet, the better. Detecting cancer in dogs early allows not only for more treatment options, but also for a better chance of treatment success.

It is always better to check than wait and wonder.

Don’t Lose Hope

Cancer in dogs is scary, but it is treatable in many cases, thanks to advances in veterinary medical care. Even with these advances, regular wellness visits and close monitoring at home are key to early detection and treatment.

If you notice any unusual signs, please reach out to your veterinarian. Acting early gives your dog the best chance for a healthy, comfortable life.