Dog Cancer Types
Start Here.
If you are here because a veterinarian used the word cancer about your dog, start with this: many canine cancers are treatable and treatment is generally far gentler on dogs than most owners expect.
If you are here because you found a lump or noticed something wrong and cancer is one of the possibilities in your head, start with this instead: most lumps on dogs are not cancer, and the only way to know is a quick test your veterinarian can often do in a single appointment.
Either way, the next section will take you where you need to go.
Find Your Dog's Diagnosis
If you already have a diagnosis, go straight to that page. Each one covers symptoms, staging, treatment options, what treatment is actually like, prognosis, and cost.
Most frequently diagnosed
- Lymphoma: Cancer of the lymph nodes and immune system
- Mast cell tumors: The most common malignant skin tumor in dogs
- Osteosarcoma: Bone cancer, usually in a limb
- Hemangiosarcoma: Cancer of blood vessel lining, often in the spleen
- Soft tissue sarcoma: A group of tumors in connective tissue
Skin, mouth, and surface
Internal organs
Head, blood, and immune system
How Common is Cancer in Dogs?
Cancer is common in dogs, and it becomes much more common with age. Roughly one in four dogs develops cancer at some point in life, and it is the leading cause of death in dogs over the age of ten, according to figures published by the Veterinary Cancer Society.
Some estimates put the rate at close to half of all dogs who live past ten.
Those numbers are worth knowing for one specific reason: they mean a cancer diagnosis is not evidence that something went wrong in how you cared for your dog.
Cancer is largely a disease of cells accumulating damage over time, which is why the strongest risk factor by far is simply living long enough. Dogs are getting cancer more often in part because they are living longer than they used to.
Breed matters a great deal. Golden Retrievers, Boxers, Bernese Mountain Dogs, Rottweilers, Flat-Coated Retrievers, and Scottish Terriers all carry elevated risk, and the pattern is strong enough that it clearly reflects inherited genetics rather than anything about how individual dogs are kept. The Morris Animal Foundation's Golden Retriever Lifetime Study has been following thousands of dogs to understand exactly this.
Size matters for certain cancers. Osteosarcoma in particular is far more common in large and giant breeds than in small ones.
Warning Signs to Watch For
The Veterinary Cancer Society publishes ten common warning signs of cancer in dogs. None of them is proof of cancer, and each has other more likely explanations, but all of them are worth an appointment.
- Swellings that persist or keep growing
- Sores that do not heal
- Weight loss without a change in diet
- Loss of appetite
- Bleeding or discharge from any body opening
- An offensive odor, particularly from the mouth
- Difficulty eating or swallowing
- Reluctance to exercise, or loss of stamina
- Persistent lameness or stiffness
- Difficulty breathing, urinating, or passing stool
Two of these deserve extra emphasis because they are so often dismissed.
Lameness in a large-breed dog that does not resolve is worth X-raying rather than treating as arthritis indefinitely. Bone cancer is painful and progresses, and it is frequently managed as a soft tissue injury for weeks before anyone images the limb.
Sudden collapse or pale gums in a middle-aged or older dog is an emergency, not something to watch overnight. It can indicate internal bleeding from a ruptured splenic tumor, and it is time-critical.
A great many dogs are diagnosed after a pet parent noticed something small and mentioned it almost apologetically. Mention it. Veterinarians would far rather examine ten benign lumps than miss one that mattered.
How Cancer is Diagnosed in Dogs
Diagnosis usually moves through the same sequence regardless of which cancer is eventually found.
Physical examination identifies what can be felt: masses, enlarged lymph nodes, an enlarged abdomen, pain on manipulation of a limb.
Fine needle aspiration draws cells from a mass with a small needle. It is quick, usually needs no sedation, and often gives an answer the same day or within a few days. This is the single most useful first test for any accessible lump.
Biopsy removes a piece of tissue, or the whole mass, for examination by a pathologist. It gives more information than aspiration, including the grade of the tumor.
Imaging shows what cannot be felt. Chest X-rays check for spread to the lungs. Abdominal ultrasound examines the spleen, liver, and other organs. CT and MRI are used for surgical planning, and MRI is required for brain tumors.
Bloodwork and urinalysis assess organ function and sometimes reveal abnormalities, such as high blood calcium, that point toward specific cancers.
Grade and stage are different things
These two are frequently confused, and the distinction changes what treatment decisions look like.
Grade describes how aggressive the tumor cells appear under a microscope. It comes from a biopsy and predicts how the tumor is likely to behave. For mast cell tumors and soft tissue sarcomas, grade is often the most important piece of information you will get.
Stage describes how far the cancer has spread through the body. It comes from imaging and lymph node sampling. For lymphoma, stage is measured differently and matters less than the specific cell type involved.
A low-grade tumor that has not spread is a very different situation from a high-grade tumor that has. Ask your veterinarian for both pieces of information, and ask what each one means for your particular dog.
