Common Types of Cancer in Dogs

We are happy to provide you with information about some common types of cancer that occur in dogs. Please remember this list is not exhaustive, so if you know or suspect that your dog has cancer, it is important to talk with a veterinary oncologist. Our team can help you with additional education, as well as diagnosis and treatment.

Lymphoma (Lymphosarcoma)

In dogs, this form of cancer most commonly causes enlargement of multiple lymph nodes. These are small structures that are located in many parts of the body, and can often be felt along the jaw, in front of the shoulders, in the armpits and groin area, and behind the “knee” area of dogs. Other sites that can be involved include lymph nodes within the chest or abdomen, as well as the spleen, liver, and intestinal tract. Because the malignant cell is the lymphocyte (a blood cell), lymphoma can occur in almost any part of the body. The diagnosis of lymphoma is usually straightforward. A sample is taken from one of the enlarged lymph nodes using a small needle (fine needle aspirate). The sample is spread onto a microscope slide and examined by a pathologist for confirmation of the disease. Once diagnosed, the oncology team may recommend different tests to stage the cancer (that is, assess how extensive the disease is within the body) and further characterize the cancer cells in order to properly recommend treatment.

While lymphoma is rarely cured, it is definitely a disease that can be effectively treated, with options ranging widely in cost and duration of disease control. The most commonly recommended treatment for lymphoma in dogs is a regimen of four different medications: prednisone, cyclophosphamide, vincristine and doxorubicin.

The medical oncology team will always provide a variety of diagnostic and treatment options to find one that will best suit you and your dog.

Bone Tumors (Most Commonly Osteosarcoma)

Bone cancer in dogs usually arises within one of the limbs. The most common breeds affected by bone cancer are large to giant breed dogs. Warning signs of this tumor include lameness and swelling at the site of the cancer. To confirm the diagnosis, X-rays of the affected bone are often followed by a fine needle aspirate of the tumor. At times, a biopsy of the tumor is also necessary for diagnosis. Because osteosarcoma tends to spread to the lungs early in the course of the disease, chest X-rays or a CT scan of the chest is also recommended (along with some basic blood tests) before decisions are made about treatment options. Ideally, no evidence that the cancer has spread to the lungs will be identified, in which case treatment with amputation followed by several treatments of the chemotherapy drug carboplatin is usually recommended.

That said, we understand that removal of a limb is not always a feasible option for dogs. Sometimes, based on location and size of the tumor in the bone, a “limb sparing” surgery is an option. Another treatment option that foregoes amputation is radiation therapy. The oncology team will certainly discuss all viable treatment options with you.

While osteosarcoma is almost always a fatal disease, our team will work with you to control the cancer for as long as possible. We understand that your dog’s quality of life is important, and we strive to give them as much happy and enjoyable time with you as possible.

Mast Cell Tumors

Mast cell tumors are the most common canine skin tumor we treat. These tumors most commonly arise on or just below the skin in dogs, although they do occasionally arise inside the chest or abdominal cavities. Warning signs of a mast cell tumor include a persistent swelling on or under the skin. These tumors are usually not painful. Diagnosis of a mast cell tumor is usually achieved by taking a sample from the swelling using a small needle (fine needle aspirate). The sample is spread onto a microscope slide and examined by a pathologist for confirmation of the disease. Once diagnosed, the oncology team may recommend different tests to determine whether the cancer has spread to other parts of the body.

Mast cell tumors are usually treated with surgery to remove the tumor. From there, our pathologists will examine the removed tissue and evaluate a number of tumor cell characteristics in order to help determine the next best steps to take. Based upon their findings, there may be no additional treatment recommendations or our oncology team may discuss radiation therapy and/or a drug called Palladia or chemotherapy with vinblastine and prednisone for your dog.

The good news about mast cell tumors is that there are many patients who can be cured of this disease. While a cure is not possible for every dog with mast cell cancer, there are a range of treatment options that can help prolong survival while maintaining a great quality of life.

Soft Tissue Sarcomas

This tumor type typically occurs as slowly growing masses anywhere in the body. Warning signs of this tumor depend upon where it is growing. When outside of a body cavity, a nonpainful mass may be the only abnormality noted. When arising within the chest or abdominal cavity, it may be difficult to identify the tumor until it is very large. Once recognized, most soft tissue sarcomas can be diagnosed by taking a sample from the swelling using a small needle (fine needle aspirate). The sample is spread onto a microscope slide and examined by a pathologist for confirmation of the disease. Following diagnosis, the oncology team may recommend different tests to determine whether the cancer has spread to other parts of the body.

Soft tissue sarcomas are usually treated with surgery to remove the tumor. From there, treatment recommendations depend on what our pathologists see when they examine the removed tissue. There may be no additional treatment recommendations or our oncology team may discuss radiation therapy to prevent the tumor from growing back. Although less common, some soft tissue sarcomas display a more aggressive behavior and will spread throughout the body to the lungs or other sites. When this is a concern, the oncology team will discuss chemotherapy or other medical treatment options with you.

Many soft tissue sarcomas in dogs can be cured with surgery plus/minus radiation therapy. Because each patient and family is different, the team will offer a variety of diagnostic and treatment options to come up with a plan that works for you and your dog.

Tumors of the Oral Cavity

Oral tumors may be benign (unlikely to spread beyond the mouth) or malignant (likely to spread to other parts of the body). The most common malignant oral tumors in dogs are melanoma, squamous cell carcinoma and fibrosarcoma. Warning signs of a tumor inside the oral cavity include worsening breath, drooling, dropping food or difficulty eating, blood or bloody discharge in the water bowl, and/or facial disfigurement. Diagnosis of an oral tumor usually requires a tissue biopsy, which is usually performed with your dog under general anesthesia. In addition to a biopsy, the oncology team will discuss other tests to assess the overall health of your dog and investigate whether the tumor has spread elsewhere in the body.

Treatment of most oral tumors relies upon surgical removal of the tumor, including removal of portions of bone that may be involved. Although this may sound extreme, dogs that have undergone surgery to remove an oral tumor along with a portion of their upper or lower jaw have excellent cosmetic and functional results within two weeks of the surgery, and are able to live happy and comfortable lives. Radiation therapy may also play a role, with or without surgery, in the management of malignant oral tumors. For melanoma specifically, immune therapies such as anti-melanoma vaccinations may be another option to consider.

While most malignant oral tumors in dogs are not curable, there is a wide range of treatment options to keep your dog comfortable and happy for as long as possible.

Nasal Tumors

There are a number of different types of cancers that can affect the nasal cavity and associated sinuses. Warning signs of nasal cancer include blood dripping from one side of the nose, sneezing, facial disfigurement or protrusion of an eyeball. In addition to cancer, other diseases that can affect the nasal cavity and cause similar signs include fungal or bacterial nasal infections, foreign bodies, and other infectious and immune-mediated causes. To determine why a dog is having these types of signs, a CT scan is usually recommended. If a mass lesion is identified on the CT scan, a biopsy should be performed to get a tissue diagnosis. In addition, other tests may be recommended to determine overall health status of the patient and to check for spread of the tumor to other parts of the body.

The most commonly recommended treatment option for dogs with nasal tumors is radiation therapy. Unless it is combined with radiation therapy, surgery is not recommended for dogs with nasal tumors because it is not possible to completely remove all of the tumor cells from the nasal cavity. Medical or chemotherapy may be an additional option, depending upon the type of cancer and the likelihood of it responding.

Although it is not possible to cure most nasal tumors, treatment can temporarily resolve clinical signs, improve your dog’s quality of life, and therefore prolong survival. The UW Veterinary Care Oncology Team will work with you to help decide the right course of action for you and your dog.