November is Pet Cancer Awareness Month

As our pets get older, they are at greater risk for certain diseases, especially cancer.

What are the signs of cancer to watch out for in your pet?

New swellings, lumps or bumps that persist and/or continue to get bigger
Abdominal swelling
Weight-loss that is unexpected
Loss of appetite or lack of interest in food
Difficulty eating or swallowing
Vomiting and/or diarrhea that is persistent and unexplained
Difficulty urinating or defecating
Bad odors – tumors in the mouth, nose, ears or rectum can cause offensive smells
Discharge from the eyes, mouth, nose, ears or rectum
Non-healing wounds, sores or unexplained bleeding
Coughing or difficulty breathing
Seizures
Lameness or evidence of pain
Unwillingness to play and interact, or loss of stamina

Although any of these symptoms are concerning, they do not absolutely mean your pet has cancer. If you are worried about your pet, it is important to consult with your veterinarian. It is also important that your pet have regular check-ups with your veterinarian. The key to successful cancer management is early detection.

The staff of the Veterinary Health Center and the hospital’s Specialist Veterinary Oncology Service are always here to help provide your pet the best care possible.

What types of cancer are most common in dogs and cats?

One in four dogs and one in five cats will develop some form of cancer in their lifetime with cancer being the most common cause of disease-related death in older animals. There are many different types of cancer which can develop in dogs and cats with some of the more common types including lymphoma, osteosarcoma, mammary carcinoma, mast cell tumors, hemangiosarcoma, melanoma, squamous cell carcinoma and transitional cell carcinoma. Interestingly, many cancers in dogs and cats are similar in nature to the same type of cancer in people. A biopsy or tissue sample is often necessary to determine the specific type of cancer present and other diagnostic tests such as x-rays, ultrasound or CT scans may be necessary to determine the extent of a tumor. Common treatment modalities available to treat cancer in pets include surgery, radiation therapy, chemotherapy, and immunotherapy and in many instances, a combination of treatment approaches may be recommended. At the Veterinary Health Center, we are able to utilize all of these approaches to treat pet cancers. We are fortunate to have veterinary medical oncologists, radiation oncologists and surgeons all specially trained to treat cancer in pets.

Lymphoma

When considering types of cancers which develop in animals, lymphoma is one of the most common to develop in both dogs and cats. Lymphoma is a type of cancer which originates in the lymph nodes or lymphatic tissues. While lymphoma can affect nearly any tissue, the lymph nodes are the most commonly affected tissue and lymph node enlargement is the most common abnormality noted in dogs with lymphoma. The majority of dogs feel well in spite of their lymph node enlargement; however, some may feel unwell. In addition to lymph node enlargement, other potential symptoms which may be present include weight loss, inappetence, lethargy, increased drinking, and increased urination, among others. Although cats can also develop lymph node enlargement, the most common form of lymphoma in cats affects the gastrointestinal tract with symptoms of weight loss, diarrhea, and vomiting being common. Because lymphoma often affects multiple lymph nodes and/or organs, systemic chemotherapy is the primary therapy utilized for treatment but surgery or radiation therapy may also be indicated in some instances. The majority of dogs and cats with lymphoma will have an excellent response to chemotherapy and typically tolerate treatments quite well.

Osteosarcoma

Osteosarcoma is the most common bone tumor to develop in dogs but is quite rare in cats. This is an aggressive form of cancer in dogs which causes swelling and bone loss at the tumor site. The majority of osteosarcomas develop in the legs of dogs but any bone can potentially be affected. In addition to swelling at the site of the tumor, many dogs will develop lameness associated with the tumor. Additional symptoms are possible depending upon the bone which is affected. Treatment for osteosarcoma involves tumor removal to relieve the source of discomfort. Due to the aggressive nature of this tumor, chemotherapy is also typically recommended to help control residual tumor cells. Amputation is often necessary for removal of an osteosarcoma if it occurs in a leg and fortunately most dogs ambulate quite well with only three legs.

Mammary Tumors

Mammary tumors are also common in dogs and cats, particularly in those who are spayed later in life. Dogs and cats who develop one mammary tumor are quite likely to develop multiple tumors in multiple mammary glands. There are many specific types of mammary tumors with approximately half of canine mammary tumors being malignant and the majority of feline mammary tumors malignant. Removal of the tumor(s) via surgery is the primary treatment for mammary tumors in both dogs and cats. Additionally, for those who have not been spayed, ovariohysterectomy is also recommended. Depending upon the type of mammary cancer, chemotherapy may also be utilized in the management of this disease.

Mast Cell Tumors

Mast cell tumors are one of the most common skin tumors to occur in dogs but they are uncommon in cats. Mast cell tumors may appear as a haired mass under the skin or they may be hairless in nature. Mast cells store histamine and therefore mast cell tumors may be red or inflamed or irritated in appearance. The behavior of mast cell tumors is quite variable with the majority being relatively benign in nature, however, some mast cell tumors grow quickly and behave quite aggressively. The behavior of a mast cell tumor can often be predicted based on the grade of the tumor as determined by a biopsy. In general, mast cell tumors are treated via surgery. Some mast cell tumors will benefit from being treated with radiation therapy and/or chemotherapy as well.

Hemangiosarcoma

Hemangiosarcoma is an aggressive type of cancer which most often occurs in the spleen of dogs. These tumors originate from blood vessels and can also develop in the heart, liver, muscle and subcutaneous tissues. The skin may also be affected but the behavior of cutaneous hemangiosarcoma is often much less aggressive than hemangiosarcomas which develop in the aforementioned sites. Because these tumors originate from blood vessels, bleeding due to a ruptured or ulcerated mass is common in dogs with hemangiosarcoma. In the case of splenic hemangiosarcoma, bleeding into the abdomen with a sudden onset of severe weakness and distended abdomen are possible. Surgical removal of the spleen or affected tissue is necessary for treatment of hemangiosarcoma. Chemotherapy may also be recommended to treat this tumor type.

Oral tumors

Oral tumors are another common location for tumors in dogs and cats. Melanoma is the most common oral tumor in dogs while squamous cell carcinoma is most frequent in cats. Both of these tumor types may be aggressive in nature. Symptoms of oral tumors include odor to the breath, bleeding from the mouth, difficulty eating or chewing, or a swelling associated with or in the mouth. A biopsy of the tissue is necessary to determine the type of cancer present. Surgical removal is the primary treatment considered for oral tumors, however, not all of them are amenable to removal. Radiation therapy and chemotherapy, or a combination thereof, are also often considered as treatment for oral tumors. Additionally, immunotherapy is frequently considered for treatment of melanoma.

Transitional cell carcinoma

Transitional cell carcinoma is the most common tumor to develop in the urinary bladder of both dogs and cats. Symptoms of a bladder tumor may include frequent urination or evidence of straining to urinate or pain with urination. Additionally, blood may be noted in the urine. Unfortunately, removal of urinary bladder tumors is not often possible due to the location of the tumor within the bladder and extensive nature of these tumors. Therefore, treatment with chemotherapy is considered the primary treatment for bladder tumors in dogs and cats. Many pets will also respond to treatment with anti-inflammatory type medications. Radiation therapy is currently being investigated as treatment for transitional cell carcinoma. Most important for patients with bladder tumors is a comfortable route for urination. Stents may occasionally be placed to allow dogs the ability to continue to urinate in spite of the continued presence of the tumor within their bladder.