7 of the Most Common Types of Cancer in Dogs

7 of the Most Common Types of Cancer in Dogs

As pet owners, we work hard to keep our dogs healthy so they can live a long, happy life. Unfortunately, many health problems are out of our control, and the diagnoses can be scary.

One of these problems is canine cancer. Cancer can affect dogs of any age, breed or size, and there are many forms of cancer that can afflict our pups. Understanding the differences between these forms of cancer can help you come to terms with your pup’s diagnosis and find the most appropriate treatment plan to help them.

The following seven types of dog cancer are the most commonly found in our pets.


Lymphoma is a type of cancer that affects your dog’s white blood cells, or lymphocytes. These cells play a critical role in your dog’s immune system.

The cancer can affect multiple areas of the body, but the most common in dogs are the lymph nodes, bone marrow, skin, gastrointestinal tract and nervous system. Experts are still unsure of what causes lymphoma to develop in dogs.

Although there is no cure for lymphoma, many dogs have success with chemotherapy and radiation treatment, which targets the cancerous cells. These forms of treatment may improve your dog’s quality of life; however, relapses are common in dogs with lymphoma, and future rounds of treatment may be necessary.


Osteosarcoma is the most common form of bone cancer found in dogs. It generally causes tumors in the limbs but can spread quite rapidly and become painful and very aggressive. Because of this, dogs diagnosed with osteosarcoma have poor prognoses.

In addition to a tumor visible on the limbs, other symptoms of osteosarcoma include lameness, weakness, swelling and joint pain. Surgery is usually required to remove the tumor, and chemotherapy may be a secondary form of treatment to ensure the cancer does not spread to other areas of the body.

Mast cell tumors

Mast cells are immune cells that live inside connective tissues. Tumors developed from these cells generally affect a dog’s skin, although they can also affect the lungs, nose and other bodily areas. For this reason, they are generally more noticeable because they can be seen or felt more easily. Unfortunately, the size and appearance of mast cell tumors are extremely variable.

During examination and diagnosis, your vet will determine the severity and “stage” of the cancer based on the tumor’s growth and differentiation from a normal, healthy cell. The later the stage, the more dangerous the mast cell tumor will be. Surgery is generally used to remove the tumor itself, while chemotherapy may be necessary to mitigate the spread of cancerous cells.

Mammary cancer

Mammary cancer, or breast cancer, is quite common in female dogs who are not spayed. Both benign and malignant tumors can develop in the dog’s mammary glands. Multiple tumors in the mammary glands are common, alongside inflammation and swelling of the lymph nodes.

Experts believe both genetics and hormones play a role in a dog’s development of mammary cancer. Spaying your female dog may significantly reduce her chances of developing this cancer.

Your vet will need to take a biopsy of the tumor to determine whether it is benign or malignant before determining the best course of treatment. Surgical removal of the tumor is the most common treatment option.

Transitional cell carcinoma

Transitional cell carcinoma is a tumor that largely affects the urinary bladder and urethra in dogs, as well as the prostate and kidneys. The cancer can cause your dog to have difficulty urinating, blood in the urine or complete urinary tract obstruction.

The tumor will need to be identified by your vet through an imaging study like an ultrasound and other tests. If the tumor is small, full or partial surgical removal may be an option. Unfortunately, larger tumors may not be able to be removed from the urethra and may require medicinal treatment or chemotherapy to halt the cancer’s spread, instead.

Lung cancer

Lung cancer, also called adenocarcinoma, is the most common form of all lung tumors in dogs and is quite common in older dogs. The malignant tumor can spread to other organs rapidly, making it quite dangerous.

Dogs with lung cancer will typically display symptoms including difficulty breathing, rapid breathing, lethargy and coughing up blood.

Surgery, radiotherapy and chemotherapy are the three most common forms of treatment for canine lung cancer, but the prognosis is generally not good.


Hemangiosarcoma is one of the most dangerous forms of canine cancer because it is characterized by extremely rapid cell growth and spreading. The cancer tends to cause tumors in the spleen and liver that spread through the blood vessels to affect the heart, lungs and other body parts.

Part of why these malignant tumors are so dangerous is because they are fed by the blood vessels, causing them to fill with blood and eventually rupture. Many dogs affected by hemangiosarcoma are not diagnosed until a tumor ruptures and causes hemorrhaging or even death.

Symptoms of this type of cancer are usually related to the organ the tumor affects, which can result in a wide range of potential signs. If symptoms are noticed and reported, early diagnosis may be possible. Surgery and chemotherapy may be used to extend your dog’s lifespan, but the prognosis for this type of cancer is generally short.

Keeping quality of life high

An elder golden retriever sits on a veterinarian's examining table waiting for results with his owner

Receiving a diagnosis of canine cancer can be devastating. Now is the most important time for you to be there for your pup. After understanding the diagnosis, your vet will advise you on the best road to take for treatment. This may include chemotherapy, radiation, and/or surgery, with a mix of natural support to help deal with your dog's symptoms. 

After the diagnosis and initial rounds of treatment, it’s important to focus on making your pup feel loved, safe and comfortable as it undergoes future treatment and continues to battle the disease.