Dog Tumors: Symptoms, Types, and Treatment

Finding out that your dog has a tumor can be scary, but there are lots of different types of tumors. Some tumors can be non-cancerous and harmless, while others can spread and make your pup sick. 

Let’s explore several of the more common types of tumors in dogs and what to do if you find one. 

What Are Dog Tumors?

Dog tumors occur when a cell continues to uncontrollably multiply instead of naturally dying (cell death). 

There are two types of tumors—benign and malignant (cancerous). 

• Benign tumors lack the ability to spread or invade other healthy tissue. Although they may need medical attention, these are not cancerous nor dangerous. 

• Malignant tumors, or cancerous tumors, spread to other organs and tissues (metastasis). Depending on the type of tumor and how aggressive it is, cancers can pose serious health risks for a dog. 

To determine how dangerous a tumor is, a veterinary visit is the best place to start.   

Types of Dog Tumors 

The most common types of dog tumors include: 

• Mast cell tumors (mastocytoma) (can be malignant or benign depending on grade) 

• Lymphoma (malignant) 

• Lipoma (benign) 

• Osteosarcoma (malignant) 

• Histiocytoma (benign) 

• Hemangiosarcoma (malignant) 

• Melanoma (can be malignant or benign) 

• Oral melanoma (malignant) 

• Papilloma (benign) 

• Mammary gland carcinoma (can be malignant or benign) 

• Thyroid carcinoma (malignant) 

Symptoms of Dog Tumors

Dog tumors usually appear like a lump that wasn’t there previously. These masses can be soft, firm, adhered or freely mobile. 

Some tumors can appear as just a spot that is a different color initially, then become a raised bump over time. 

Tumors can be hairless, haired, pink, pigmented, ulcerated, or knobby. 

If you notice any spot on your dog’s body that is changing in color, size or texture, have it checked out by your veterinarian. 

Causes of Dog Tumors

The cause of dog tumors can be complex. 

Cells grow, divide, perform their job, and ultimately die and are replaced by new cells to keep the body going. 

However, sometimes the DNA within the cell can become damaged, causing a cell to mutate or divide incorrectly. If a mutated cell is left in the body, it may continue to grow into a tumor or cancer. 

Damage to the cells may be triggered by many factors, or more likely a combination of factors.  Let’s look at possible contributing factors: 

• Genetics. Some types of tumors occur more frequently in certain breeds, such as Golden Retrievers, Boxers, Bernese Mountain Dogs, and Rottweilers. 

  • This suggests a possible hereditary or genetic component, but more research is needed to better define which dogs are at risk of developing specific cancers. 

• Age. Malignant tumors occur more frequently in older pets. The exact link between cancer and age is not fully understood, but it’s believed to be linked to a weakening immune system as pets age. 

  • As bodies age, it becomes more likely that a mutated cell will get past the body’s defense mechanisms and result in cancer.  

• Environment. Environmental hazards or chemicals can increase the risk of cancer in people—and the pets that live with them. 

  • Some examples include a variety of herbicides, pesticides, and other chemicals. Substances such as nickel, uranium, radiation, and asbestos have all been shown to be carcinogens. Prolonged exposure to the sun, cigarette smoke, and UV light may result in higher cancer risks.  

How Veterinarians Diagnose Dog Tumors

If you find a lump or bump on your dog, don’t panic. Schedule an appointment with your vet to get the growth checked out. 

Your vet can’t diagnose a dog tumor based on touch. To get an accurate diagnosis, your vet will perform a fine needle aspirate (FNA) or a biopsy. 

These results will let both you and your vet know how serious the tumor is and what the recommended next steps should be.  

Dog Tumor Staging 

Dog tumors are staged somewhat differently than human tumors. 

Depending on the type of tumor (benign or malignant), they may be staged numerically with Roman numbers ranging from 0 to IV. Tumor staging is done to determine how much it has spread. 

Staging is different from “grading.” Tumors are graded to determine how aggressive they are. Grading can indicate how fast the tumor will grow, while staging will help shed light on how far it has spread. 

A higher number means the cancer has spread further. Different types of tumors are graded differently. 

Dog Tumor Treatment

The treatment recommended for a dog’s tumor depends on several factors: 

• How aggressive you want to be with treatment 

• Whether the tumor is one that typically spreads to other organs or stays locally invasive 

• How advanced or large the tumor is (the grade) 

• How serious the tumor-related symptoms are 

Treatment options include surgical removal, radiation, immunotherapy, and chemotherapy. 

Prednisone is sometimes used in conjunction with traditional chemotherapy drugs to achieve comfort in some cancer patients. 

If your dog experiences an upset stomach with cancer treatment, they may be prescribed Cerenia to help with nausea. 

If your dog is experiencing pain with their cancer, they may be prescribed various adjunct pain medications like gabapentin or amantadine. 

Recovery and Management

Some types of dog tumors can be cured. These are usually tumors that are benight, or locally invasive and can be completely removed surgically. 

Types of cancerous tumors that spread or metastasize to other parts of your dog’s body can be managed with treatment but are, unfortunately, not usually curable. 

The good news is that cancer treatment in dogs is often well tolerated with minimal side effects. 

For example, chemotherapy in dogs does not typically cause hair loss and has only mild gastrointestinal side effects, like an upset stomach. You can even administer some chemotherapeutic drugs at home, which decreases stress for your pet. 

When your pet is diagnosed with cancer, it’s best to get as much information as possible before you start making decisions. 

A consult with a veterinary oncologist can help provide answers around your dog’s possible outcomes and what to expect. They can explain treatment options in terms of what each one means as far as longevity and quality of life for your pet. 

Even if you ultimately choose not to proceed with chemotherapy or radiation, the more knowledge you are equipped with, the more at peace you will be with your decisions. 

Dog Tumor Prognosis 

Prognosis varies depending on what type of tumor your dog has been diagnosed with. 

Benign dog tumors usually have an excellent prognosis and are often curable with surgical removal. 

Malignant tumors carry a more guarded prognosis. While some malignant cancers can be treated with chemo and remission achieved (like lymphoma), affected dogs will always eventually come out of remission. 

When discussion prognosis for malignant tumors, the conversation is usually centered around how much quality time we can get for affected pups with various treatment options.