7 Most Common Cancers in Dogs | PetFirst
7 Most Common Cancers in Dogs
Pet Care & Health

7 Most Common Cancers in Dogs

by PetFirst Pet Insurance
2 years ago

No pet owner wants to hear the news that their dog has been diagnosed with cancer. Unfortunately, many will hear this news as cancer is the leading cause of death in dogs over 10 and often occurs in younger dogs, too.

Here are the signs, symptoms, and treatments of the seven most common canine cancers so you can better be prepared as a dog parent.


Melanoma tumors are common in dogs, although some tumors are benign. PetMD explains that benign melanomas are often found on a dog’s head, toes, or back; they are ¼ inch to 2 inches in diameter and are usually round, raised mass. 

Malignant (cancerous) tumors might be found on a dog’s mouth, eye, or face. Malignant melanomas cause lymph nodes to swell. A vet can take a biopsy of a tumor to see whether it is malignant or if it is spreading.

Melanoma is generally treated by removing the tumor. If the cancer has already spread, however, vets may try chemotherapy or a melanoma vaccine, although these do not have high rates of success. The best option is catching the tumor before it spreads.


Osteosarcoma is the most common type of bone tumor found in dogs.

Although bone cancer can affect any dog, larger breeds are particularly susceptible (especially large dogs in-between four and seven years old).

Bone cancer is very aggressive and tends to spread quickly throughout the body. Symptoms of bone cancer might include joint pain, swelling, and fatigue, as well as inflammation around the tumor. 

Bone cancer is difficult to treat and comes with many side effects. Unfortunately, most dogs undergo amputation of the limb with the tumor and then proceed to chemotherapy. If you have a large breed of dog that suddenly becomes lame for no apparent reason, have your vet check for bone cancer right away. 

Lung Cancer 

Lung cancer is common among older dogs and can be diagnosed through an X-ray or CT scan.

If there is just one tumor, surgery is commonly recommended. If the cancer has already spread, chemotherapy may be used.

Adenocarcinoma of the lung is a fast-growing cancer that makes up 75 percent of all primary lung tumors in dogs. Symptoms could include pain, lethargy, difficulty breathing, poor appetite, and fever. 

Mast Cell Tumors 

Mast cells are located in the connective tissues that are close to a dog’s external surface (lungs, skin, nose).

Mast cell tumors are a type of skin cancer. They’re very common, making up 20 percent of all skin tumors in dogs.

Symptoms of a mast cell tumor might include a mass lesion (look for redness, bruising, or fluid buildup), swollen lymph nodes, and loss of appetite or vomiting.  

Several treatment options are available for mast cell tumors.

Surgery, chemotherapy, palliative therapy (pain killers), radiation therapy, and stereotactic radiation (more advanced radiation therapy) are all choices that your vet might suggest. 


Lymphoma is a cancer of lymphocytes (blood cells) and lymphoid tissues. (Lymphoma is very similar to non-Hodgkin’s lymphoma in people.)

The four most common kinds of canine lymphoma are multicentric lymphoma, alimentary lymphoma, mediastinal lymphoma, and extranodal lymphoma.

Symptoms differ according to each type. Vets can diagnose lymphoma through a fine-needle aspiration and generally treat the cancer through chemotherapy.

Mammary Cancer 

Mammary tumors are common in female dogs and tend to be rarer in males.

The American College of Veterinary Surgeons explains that mammary tumors are common in female dogs who were either not spayed until after two years of age, or never spayed at all.

Poodles, dachshunds, and spaniels most commonly get mammary tumors – and obesity at a young age can increase the risk of this cancer.

Most mammary tumors are surgically removed and sometimes chemotherapy is recommended after the surgery.


Hemangiosarcoma is an extremely dangerous and fast-moving cancer of the blood vessel walls that can cause tumors anywhere in a dog’s body (although heart/spleen tumors or skin tumors are most common). It is most common in Golden Retrievers, Labrador Retrievers, and German Shepherds.  

Symptoms displayed might include lethargy, collapse, increased heart and respiratory rates, and pale mucous membranes.

Since this cancer often does not receive a diagnosis until it’s very advanced, pet owners often have to make a quick decision regarding whether to do emergency surgery and remove the tumor (which may begin hemorrhaging during the diagnostic process) or euthanize the dog. 

Affordable Health Care for Your Dog 

health insurance plan for your dog is the best way to ensure he always has access to medical care without breaking the bank.  

Pet insurance provides peace of mind that if your pet gets sick or injured you don’t have to think twice about the financial aspect and you can just focus on your pet’s care.

The team at PetFirst Pet Insurance loves helping pet parents have the ability to give their pets the best care possible. As a pet parent, you can find the best coverage for your furry friend with PetFirst and our various options that fit your families needs.

Pet health insurance through PetFirst can help you offset the costs of a variety of medical conditions in your dog or cat.

PetFirst is here for you during difficult times such as surgery or chemotherapy — let us give you a free quote today. 

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