Common Signs of Cancer in Dogs

Knowing how to recognize the common signs of cancer in dogs is one of the best ways you can protect your canine companion.

· 7 min read

Knowing how to recognize the common signs of cancer in dogs is one of the best ways you can protect your canine companion.

Dogs are similar to humans in a lot of ways. They come in many shapes and sizes, and all have distinct personalities, characteristics, behavioral traits, and emotions. Our furry friends are also, unfortunately, susceptible to a range of ailments, from arthritis and heart problems to infections and diabetes. For older dogs, cancer is a particularly common threat.

Approximately 1 in 4 dogs will develop cancer at some point in their lives, but the risk of cancer developing increases over time. Approximately 50% of all dogs over the age of 10 will develop cancerous growths, making cancer the leading cause of death in senior canines.

The good news is that when cancer symptoms are caught early, many forms of dog cancer are treatable. Knowing which signs and symptoms to look out for ensures you can get your dog the treatment they need fast, and improve their chances of survival.


Common Symptoms of Cancer in Dogs

Cancer in dogs is very similar to cancer in humans. The condition is a result of abnormal cells growing throughout the body, which can destroy normal tissues and create painful masses. Notably, there are many different types of cancer which can affect canines.

The form of cancer your dog experiences will influence its symptoms. Some versions can cause painful lumps and bumps, while others lead to weight loss and appetite changes. Some of the most common overall symptoms of cancer in dogs to watch for include:

·         Unusual growths: Lumps and bumps on or under your dog’s skin are a common sign of cancer. It’s worth examining your pet regularly during their grooming routine to check for any growths you didn’t notice before.

·         Slow healing: If your dog gets an accidental injury and suffers from sores or open wounds which fail to heal rapidly, this could be a sign of a problem with their immune system.

·         Appetite changes: When cancerous cells are affecting your pooch, their food consumption may dwindle. They may eat less and lose weight as a result.

·         Vomiting and Diarrhea: Some forms of cancer can cause your dog to have runny stools or vomit more than usual.

·         Bad odor: Tumors around the anus, nose, and mouth can sometimes lead to bad smells, particularly when discharge is involved.

·         Lethargy: Most dogs require regular exercise to stay healthy. If your pooch is less interested in exercise or play, this could be a sign something is wrong.

·         Mobility issues: If your dog attempts to walk and play as normal, but often limps, or appears stiff in their movements, this could indicate nerve, bone, or muscle cancer.

·         Bathroom issues: Some forms of cancer can make it difficult for your dog to go to the bathroom normally. Watch for signs of wheezing or wining when urinating or pooping.

While all of these symptoms can sometimes be signs of cancer in dogs, they can also indicate the presence of other ailments, such as arthritis, or infection. Don’t panic if you notice one of these signs, but do make sure you seek veterinary help immediately.


The Symptoms of Different Types of Cancer in Dogs

As mentioned above, though there are general symptoms associated with cancer in dogs, there are also some symptoms which are more likely to appear in connection with specific cancer. Let’s take a look at how some of the most common types of cancer present themselves.

1. Melanoma

Melanoma is a form of skin cancer. In dogs, this cancer usually creates round masses, between a quarter inch and 2 inches in size. These growths can appear anywhere on your dog’s body, and may be hidden beneath patches of fur. If you can’t find any growths, look for swollen lymph nodes. Inflammation around the ears, necks, and underneath the arms can be quite common symptoms as well.

Melanoma can often be treated with the removal of the tumor, as well as certain medications. However, the condition does need to be detected early. Regularly check your dogs’ eyes, toes, and other areas for unusual masses.

2. Mammary Cancer

Similar to breast cancer in humans, mammary tumors typically affect female dogs, but they can also occur in males. Notably, these types of cancer are most likely to emerge in female dogs who have not been spayed, or were not spayed before they reached 2 years of age.

Certain breeds of canine are also more susceptible to this cancer, such as poodles, dachshunds, and spaniels. Watch for lumps around the nipples on your dog’s body, and unexpected discharge. Your pet may also exhibit signs of weakness, restlessness, or excessive panting. New issues with anxiety, excessive drinking and urination are also common with mammary cancer.

3. Osteosarcoma

Osteosarcoma is the most common form of bone cancer in dogs. It appears most often in larger dogs, with bigger bones and joints. This cancer often occurs when your puppy’s limbs are growing rapidly as they enter adulthood. It usually appears around your dog’s legs, but can also develop on the bones of the spine, skull, and ribcage.

The symptoms of this condition can vary, but often include swelling around the tumor site, close to the joints and muscles. Perhaps the most common sign of Osteosarcoma in dogs is a sudden inability to walk normally, or a stiffness in the joints. If your dog stops moving as often, or avoids playing as much as they once did, seek advice from a vet.

4. Lung Cancer

Lung cancer is relatively common in senior dogs, and often requires surgery as part of a treatment process. There are various forms of lung cancer which can affect canines, such as “adenocarcinoma” of the lung, which makes up about 75% of all primary lung tumors in dogs.

Since the tumors connected to lung cancer are located inside of your dog’s body, this cancer can be harder to detect in its early stages. The best signs to look out for include sudden lethargy, difficulty breathing, or wheezing. Regular coughing could also be a symptom of this condition.

5. Mast Cell Tumors

Otherwise known as “basal tumors”, mast cell tumors emerge in the connective tissues beneath the skin. This form of cancer is quite common in all kinds of dogs. However, the growths are usually benign, making them relatively easy to treat.

Unexpected lumps and growths are the key sign associated with mast cell tumors. If you notice a hard bump underneath your dog’s skin when you’re stroking or grooming them, contact your vet. Some tumors can appear as clusters of bumps which form in the same general space.

6. Hemangiosarcoma

This is one of the most dangerous forms of cancer in dogs. Hemangiosarcoma is a form of cancer which affects the blood vessel walls throughout your dog’s body. This canine condition often occurs throughout the skin, heart, and spleen. However, it can affect virtually any part of a dog. Some breeds are more susceptible, such as Labrador Retrievers, and German Shepherds.

This cancer is quite tricky to spot in dogs, as it doesn’t usually cause growths and lumps. However, you might spot signs such as a loss of appetite, weakness, lethargy, and pale mucous membranes around your dog’s mouth and eyes.

7.  Lymphoma

Canine lymphoma is a form of blood cancer, which is very similar to non-Hodgkin’s lymphoma – a condition common in people. There are different forms of lymphoma which can affect canines, including “multicentric” lymphomas which affect the entire body, and “alimentary lymphoma” which forms mainly within the gastrointestinal tract.

Certain types of lymphoma can also affect specific parts of the body, such as the chest, and the organs outside of the lymphatic system. The symptoms of this type of cancer vary depending on where the tumors form. Watch out for loss of appetite, weight loss, swelling of the legs and face, and increased thirst or urination.

Diagnosing Cancer in Dogs

Spotting the symptoms of cancer in dogs isn’t always easy. While some signs are relatively clear, such as new lumps and growths, others may go unnoticed, such as lethargy or personality changes. If your dog is acting abnormally, you see changes to its skin or fur, or you notice anything else that you feel may be a cause for concern, it’s important to seek assistance from a vet.

Vets will be able to conduct ultrasound and CT scans to search for tumors hidden beneath the surface of the skin. They can also conduct tests to determine whether growths are cancerous or benign. Depending on the form of cancer, your vet will also provide you with options for treatment, which usually include surgery, radiation therapy, and chemotherapy.

One of the best ways to protect your dog from less visible forms of cancer is to get a DNA test for dogs to detect potential genetic risks of certain cancers.

The CirclePAW DNA test for dogs can detect your canine’s genetic cancer risk by looking at their DNA.

Order your test today so you can stay one step ahead of this life-threatening illness, and ensure your pup stays healthy for years to come.


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  2. VCA Hospitals: Osteosarcoma in Dogs - VCA Animal Hospitals.
  3. Petcureoncology: Learn About Lung Cancer In Dogs | PetCure Oncology. adenocarcinoma is the most,before they are finally diagnosed.
  4. ACVS: Mammary Tumors.
  5. Morris Animal Foundation: Hemangiosarcoma – A Deadly Canine Cancer That Strikes Without Warning.