5 Common Types of Cancer in Dogs and What to Look For

Getting a cancer diagnosis for your dog can be scary. There are hundreds of types of cancer out there and it can be hard to know what to look for. To help you understand the basics, we've compiled five of the most common types of dog cancer, including symptoms, treatment options, and at-risk breeds below.

1. Lymphoma/Lymphosarcoma

Lymphoma is a proliferation of cancerous lymphoid cells in the lymph nodes or other organs of the body. In dogs, these cells most often originate in the lymph nodes. The cancerous cells then spread systemically to other parts of the body. It is not yet known what causes lymphoma to develop in some dogs, and research into this topic is ongoing.¹

Symptoms of lymphoma in dogs

One of the first symptoms of lymphoma that pet owners may notice at home is enlarged lymph nodes.² These may look like swellings under the jaw, in the armpits, in the groin or behind the hind legs. Other symptoms of lymphoma in dogs can include non-specific signs such as:³

• Decreased appetite.
• Lethargy.
• Weakness.
• Vomiting.
• Diarrhea.
• Increased drinking and urinating.
• Fever.

Lymphoma treatment options and cost

The treatment for lymphoma is chemotherapy. Several chemotherapy protocols exist for the treatment of lymphoma, but the CHOP protocol or the University Wisconsin-Madison 25-week protocol (UW-25) are generally considered the most effective treatments.³ These protocols use multiple chemotherapy drugs administered at regular intervals to achieve remission. Throughout the process, the patient's complete blood count is monitored to ensure the immune system is not overly impacted by the treatment. At the end of the protocol, the patient may be placed on a maintenance protocol or may not need to continue chemotherapy further, depending on individual patient factors.

Chemotherapy and its associated monitoring are expensive and costs can add up quickly. Dog owners pursuing this treatment option should expect to spend several thousand dollars on treatments and associated monitoring costs.

Lymphoma prognosis

The prognosis for lymphoma depends on a number of factors, including the stage, cell type, substage and grade of the disease. High-grade lymphoma in dogs typically has a poorer prognosis than low-grade lymphoma.¹ Dogs with B cell lymphoma treated with combination chemotherapy have survival times of approximately 12 months, while those with T cell lymphoma have survival times closer to six months.¹ Without chemotherapy treatment, lymphoma is typically terminal within one to two months.²

Prevention of lymphoma

Unfortunately, because we do not yet know what causes lymphoma in dogs, there are no clear ways to prevent it. In predisposed breeds, it is prudent to avoid breeding dogs from at-risk genetic lines.

Dog breeds at risk for lymphoma

• Golden Retriever
• Boxer
• Basset Hound
• English Bulldog
• West Highland White Terrier
• Border Collie
• Labrador Retriever
• American Cocker Spaniel
• Siberian Husky
• Yorkshire Terrier
• Australian Shepherd
• Irish Wolfhound
• Shih Tzu
• German Shepherd
• Rottweiler

2. Mast Cell Tumors

Mast cell tumors are the most common type of skin tumor in dogs. They can also affect other areas of the body, including the spleen, liver, GI tract and bone marrow.⁴ A mast cell tumor on the skin can have a variable appearance. Often they appear as a raised bump on or under the skin surface. They may be red, hairless, or ulcerated.⁴ Sometimes they look very similar to other types of tumors, which is why it is very important to have new or changing skin growths checked by your veterinarian.

Symptoms of mast cell tumors in dogs

Mast cell tumors are most commonly noticed by owners as a new lump or bump on the skin surface or under the dog's skin. Other symptoms of mast cell tumors in dogs may include:⁵

• Ulcerated tumors
• Tumors that vary in size from day to day
• Vomiting
• Lack of appetite
• Anemia
• Abdominal pain
• Digested blood in the stool

Mast cell tumor treatment options and cost

Surgical removal of the mast cell tumor is the preferred treatment and may be curative in some cases.^4,5 During surgery, the surgeon will take wide margins around the tumor, meaning that they will also remove some normal tissue, to ensure that all the microscopic cancer cells are removed.⁵ In cases where some tumor cells must be left behind, radiation therapy may be used as an adjunct treatment for local tumor control.⁴ Chemotherapy may be used in cases of high-grade tumors or when mast cell tumors have spread to other organs.⁵

The cost for mast cell tumor treatment varies depending on the type of treatment, the size of the tumor, the type of facility providing care, and the geographic location. For surgery, pet owners should expect to spend $1000 to $3000 depending on the size and location of the tumor to be removed.

Mast cell tumor prognosis

The grade of the tumor directly relates to the prognosis. In order to determine the tumor grade, the tumor must be removed and evaluated by a pathologist.⁵ Low-grade tumors are associated with a good prognosis, especially if they can be completely removed.⁴ Mast cell tumors occurring in areas other than the skin or those that have spread to distant organs are associated with a poor prognosis.⁴

Prevention of mast cell tumors

Unfortunately, there is no known way to prevent mast cell tumors in dogs.

Dog breeds at risk for mast cell tumors⁵

• Boxers
• Boston Terriers
• Pugs
• Bullmastiffs
• Cocker spaniels
• Bull terriers
• Staffordshire terriers
• Fox terriers
• Labrador retrievers
• Golden retrievers
• Beagles
• Schnauzers
• Weimaraners

3. Mammary Tumors

Mammary (breast) tumors in dogs are common, particularly in intact (un-spayed) females and those spayed after their first heat.⁶ In dogs, the majority of mammary tumors are benign, while about 45% of mammary tumors are malignant (cancerous).⁷ The cause of mammary tumors is still unknown, but obesity is thought to be a risk factor.⁷

Symptoms of mammary tumors in dogs

Dog owners typically first notice a lump in the mammary chain. Other symptoms of a mammary tumor can include:⁶

• One or more swollen glands.
• Discharge from one or more glands.
• Pain.
• Ulceration of the skin of the affected gland.
• Lethargy.
• Weight loss.

Mammary tumor treatment options

Surgery is recommended to remove either the mass alone or the entire affected mammary gland, depending on the size, location and number of mammary tumors involved.⁸ Chemotherapy has not been shown to be effective in the treatment of mammary tumors.⁷

In cases of inflammatory carcinoma, surgery is not an effective treatment and does not improve survival rates.⁸ Instead, a combination of radiation therapy and medical management with NSAIDs (non-steroidal anti-inflammatory drugs) is recommended.⁶

Mammary tumor prognosis

Tumor size is an important prognostic factor for mammary cancer in dogs. If the mass is small (3 to 5 cm or smaller) the less likely it is to recur after surgical removal or spread to other areas of the body.⁸ Other prognostic factors include the tumor type, grade and the clinical stage of the disease at the time of diagnosis.

Prevention of mammary tumors

Mammary tumors can be prevented by spaying prior to the first heat cycle, feeding a well-balanced diet, avoiding obesity and avoiding the use of hormones such as estrogen and progesterone.⁸

Dog breeds at risk for mammary tumors

• Poodle
• Chihuahua
• Dachshund
• Yorkshire Terrier
• Maltese
• Cocker Spaniel
• English Springer Spaniel
• English Setter
• Brittany Spaniel
• German Shepherd
• Pointer
• Doberman
• Boston Terrier

4. Hemangiosarcoma

Hemangiosarcoma is a highly malignant cancer of the cells that line the blood vessels. Although hemangiosarcoma can technically occur in any part of the body, it is most common in the spleen, the liver, the right atrium of the heart, and the skin.⁹ Hemangiosarcoma is the most common malignant tumor of the spleen.¹⁰ This type of cancer is usually seen in older, large breed dogs.¹⁰

Symptoms of hemangiosarcoma in dogs

Because hemangiosarcomas often occur internally, dog owners may not notice any symptoms. Sometimes, the first symptom noticed is collapse due to internal bleeding. Other symptoms of hemangiosarcoma can include:¹⁰

• Pale mucous membranes
• Increased heart rate
• Increased respiratory rate
• Distended abdomen
• Weight loss
• Lethargy
• Loss of appetite
• Fainting or weakness

If the hemangiosarcoma occurs on the dog's skin, symptoms can include:⁹

• Raised, red or purple swelling on the skin.
• Soft or firm swelling under the skin.
• Spontaneous bruising or bleeding.

Hemangiosarcoma treatment options

Surgery to remove the hemangiosarcoma is the recommended treatment.¹⁰ For some dogs, chemotherapy may be recommended to delay the progression of metastatic disease.⁹ Treatment for hemangiosarcoma can be costly, and some dogs may require blood transfusions to treat the blood loss due to a ruptured hemangiosarcoma tumor. Dog owners should expect to spend several thousand dollars on hemangiosarcoma treatment, and more if chemotherapy is also to be included in the protocol.

Hemangiosarcoma prognosis

Unfortunately, with surgery alone, the survival time for dogs with hemangiosarcoma is typically two to three months or less, and most dogs die of metastatic disease.¹⁰ With surgery and chemotherapy, survival time may be increased to six to eight months.¹⁰

Prevention of hemangiosarcoma

It is not yet known what causes hemangiosarcoma in dogs, and there is no clear way to prevent it.

Dog breeds at risk for hemangiosarcoma¹⁰

• German Shepherds
• Labrador Retrievers
• Poodles
• Golden Retrievers

5. Osteosarcoma

Osteosarcoma is the most common bone tumor in dogs, and approximately 85% of all skeletal tumors in dogs are osteosarcoma.^11-14 Osteosarcomas most commonly occur on the limbs but can also occur in other parts of the body such as the skull, pelvis and ribs.¹¹ Osteosarcomas most commonly affect middle-aged and older large and giant breed dogs, though any dog can be affected.¹² The exact cause of osteosarcoma is unknown.¹³

Symptoms of osteosarcoma in dogs

The first symptom pet owners typically notice is limping on the affected limb.¹³ Other symptoms of osteosarcoma in dogs include:¹¹

• Swelling of the bone or the surrounding soft tissue.
• Pain
• Irritability
• Aggression
• Loss of appetite
• Weight loss
• Sleeplessness
• Reluctance to exercise
• Pathologic fractures

Osteosarcoma treatment options

Treatment of osteosarcoma includes amputation of the affected limb and chemotherapy.¹⁴ Unfortunately, 90% to 95% of dogs with osteosarcoma already have microscopic metastatic disease by the time they are diagnosed.¹³ Chemotherapy is used to treat metastatic disease and prolong survival times.¹¹ The most commonly used chemotherapy drug is Carboplatin, which is given by injection once every three weeks for a total of four treatments.¹¹

Osteosarcoma prognosis

Without treatment, dogs with osteosarcoma die within several months, while those treated with a combination of surgery and chemotherapy may see double the survival times.¹⁴ About half of dogs treated with surgery and chemotherapy will be alive one year after diagnosis.¹²

Prevention of osteosarcoma

Because it is not known what causes osteosarcoma in dogs, there is no clear way to prevent this disease.

Dog breeds at risk for osteosarcoma

• Rottweiler
• Great Dane
• St. Bernard
• Irish Setter
• Irish Wolfhound
• Doberman Pinscher
• German Shepherd
• Rhodesian Ridgeback
• Golden Retriever

CareCredit Financing for Dog Cancer Treatment

Canine cancer is complex and we're still learning more about it every day. If your dog needs cancer treatment, the costs can add up quickly. Fortunately, the CareCredit credit card can help you manage the costs of your dog's veterinary care, including treatments like surgery and chemotherapy.* Use our Acceptance Locator or download the CareCredit Mobile App to find a veterinarian near you who accepts the CareCredit credit card.

Author Bio

Dr. Elizabeth Racine is a small animal general practice veterinarian and freelance writer. She covers both human and veterinary medicine with a special interest in nutrition, internal medicine, and veterinary behavior.