About Pet Cancer

Cancer is a group of diseases in which abnormal cells grow without control, they invade surrounding tissues and ultimately spread to organs throughout the body. There are more than a hundred specific cancer types, each showing unique behaviors and requiring tumor specific treatment strategies. In a normal body, new cells (which form the structures of the body and control its functions) are constantly being made to replace old or damaged cells. This process is very well regulated with a delicate balance existing between cell multiplication and cell death to maintain the right number of cells. When this process goes wrong and the body begins to produce more cells than it needs and/or cells don’t die when they should, the extra cells may undergo genetic changes and can then form a mass called a tumor.

Tumors can be either benign (noncancerous) or malignant (cancerous). Benign tumors typically remain localized to one place and do not invade surrounding tissues or distant organs. They are not usually dangerous but can cause medical problems once their size begins to compress surrounding tissues. In contrast, malignant tumors contain cells that have the ability to invade neighboring tissues and spread to distant organs via blood circulation or the lymphatic system, a process known as metastasis.

Cancer has become the number one cause of death in older cats and dogs. It accounts for about 50% of pet deaths per year. Though cancer takes many lives, it is for the most part a treatable disease, comparable to diseases like heart failure or kidney failure. There have been many advances in the treatment of cancer that can provide owners alternatives for giving their pets a high quality of life for years to come.

Advances in the detection and treatments of cancer for both pets and humans are significant, but early diagnosis is important in order to have better outcomes to treatments. For diagnosis pets normally require a series of tests to determine if it is cancer, which type of cancer, where is the cancer located, how fast it is growing, and the malignancy of the tumor.

We at TVCR honor the important relationship between the owner, pet, and referring veterinarian to insure that all parties are kept with up-to-date information of the best care options for your pet.

Canine Tumors

Insulinomas

An insulinoma is a malignant tumor of the pancreas that causes excessive secretion of insulin, leading to low blood sugar concentration. Insulinomas usually occur in middle-aged to older dogs, with an age ranging from eight to twelve years. They are very rare in cats and there is no gender predilection. These tumors can occur in any breed of dog. Irish setters, boxers, golden retrievers, German shepherds, poodles, and Labrador retrievers are breeds that have shown a higher incidence. Medium to large-sized breeds of dogs are most commonly affected.

Surgery has been shown to have better rates of tumor remission than regular medical management, though the later is recommended in the case of multiple primary tumors and metastasis. Medical therapy has been known to prolong live in affected canines.

Chondrosarcoma of the Bone in Dogs

Chondrosarcoma of the bone is a malignant form of cancer with a tendency to spread swiftly, which, if not diagnosed and treated early, can be life threatening. Chondrosarcoma arises from the connective tissue that is found between the bones and joints, often metastasizing to other parts of the body, including, but not limited to the ribs. This is the most common rib tumor found in dogs, and the second most common primary tumor in dogs. The majority of Chondrosarcomas involves flat bones, with a high percentage occurring in the nasal cavity. This form of cancer also may affect the limbs, with a resulting weakening in the structure of the bone that can lead to fractures. Large breeds are at higher risk, as well as older dogs, but it has been found in dogs of almost all ages.
Chondrosarcomas may cause lameness if affecting the legs, pain, swelling around the tumor site, sneezing, discharge and/or nose bleed and difficulty breathing if the tumor is located in the nasal cavity. This highly aggressive and life-threatening tumor requires prompt treatment. Amputation or limb salvage is usually recommended in cases where there is no metastasis (spreading) of the tumor in the affected limb. For nasal tumors, radiation therapy is normally the treatment of choice. Radiotherapy may also help in prolonging the lifespan in those dogs in which tumors are inoperable. If the tumor involves the ribs, your veterinarian may decide to remove the affected ribs and nearby lung tissues through a wide excision in order to prevent metastasis. Chemotherapy is recommended, but the effectiveness of this therapy has not yet been fully evaluated for this type of tumor. Currently, surgery is the only treatment given for this disease.

Hemangioma and Hemangiosarcoma in Dogs

Hemangiomas are normally observed as red-to-black nodules that may appear singularly or in multiple areas. Sarcomas are cancers of connective tissue, blood vessels, or the fibrous tissue that surrounds and supports organs. When used together, these two terms refer to hemangiosarcoma, which is a cancer of blood vessels, usually occurring in the spleen, heart or skin.
Hemangiosarcoma usually develops slowly and painlessly until it reaches an advanced stage. The disease can occur as a single tumor within one major organ or multiple tumors throughout the body. According to the National Canine Cancer Foundation, advanced staged tumors “are resistant to most treatments.” The normal therapy for this tumor is surgery and intensive chemotherapy. Hemangiosarcoma occurs most commonly in large breed dogs with an age ranging from eight to 10 years.
The average time from discovery of the (hemangiosarcoma) tumor until death in affected dogs is six to eight weeks, but unfortunately death occurs more rapidly in a number of cases. This type of tumor is known to spread, or metastasize quickly. Signs of the disease can range from subtle to overt, and may include unexplained weakness, nosebleeds, pale mucous membranes, abdominal swelling and depression, or collapse and sudden death.
Diagnosis often requires radiographs, lab tests and exploratory surgery, though sometimes the tumor may be large enough to be felt during normal physical evaluation. Veterinarians may also aspirate fluid from the abdomen (abdominocentesis) and/or perform an abdominal ultrasound to identify masses.

Canine Lymphosarcoma (LSA)

Lymphosarcoma is a tumor caused by a cancerous proliferation of lymphocytes (cells that normally function in the immune system); it is one of the most common tumors seen in dogs. It affects dogs of any breed and age, although most dogs will be middle-aged or older at the time of diagnosis; Golden retrievers are considered a breed at increased risk of developing LSA.
The symptoms present in canines with this type of tumor are highly variable as lymphocytes can be found in virtually any organ in the body. The most common form (referred to as stages) of LSA causes a non-painful enlargement of one or more lymph nodes that can be seen or felt from the body surface. A lymph node may become enlarged enough to impair function (obstruction of blood flow or airway). Other forms of the tumor may involve the liver, spleen, bone marrow, gastrointestinal tract, skin or nervous system (and other organs) and the clinical signs will reflect the organ system involved (e.g. vomiting or diarrhea with gastrointestinal forms; weakness or pale mucous membranes and others that reflect impaired production of blood cells from the bone marrow). Canines affected with the disease may simply feel ill with any of the different forms. In some dogs, lymph node enlargement is an incidental finding when an otherwise healthy-appearing dog is seen by a veterinarian.
The treatment for Lymphosarcoma is mainly chemotherapy drugs; the best responses in terms of length of tumor control and survival rates are generally seen with protocols that include administration of more than one chemotherapy drug, although there are treatments that involve administration of a single drug. In some dogs with localized disease, surgery or radiation therapy can be a good treatment, although chemotherapy is still often recommended in these cases.

More Type of Pet Cancer: Squamous Cell Carcinoma, Mast Cell Tumors and Basal Cell Carcinomas

Squamous Cell Carcinoma

Squamous cell carcinomas have been recognized in all domestic animals. Most cases of these tumors originate without cause, in a broad range of species, prolonged exposure to sunlight has been determined as a major predisposing factor. In cats a unique form of feline squamous cell carcinoma is associated with papilloma virus infection. These tumors are the most frequently diagnosed carcinomas arising in the skin of canines. Two forms are recognized; cutaneous squamous cell carcinomas are tumors of older dogs, with Bloodhounds, Basset Hounds, and Standard Poodles at greatest risk. The lesions may appear in areas like the head, paws, abdomen, among others, and they possess a firm appearance, raised above normal skin level, frequently ulcerated and nodular. The common treatment for this type of tumors is surgical excision followed by radiation therapy or chemotherapy (depending on the severity of the tumor).

Mast Cell Tumors

These tumors are the most frequently recognized malignant or potentially malignant tumors of dogs. This cancer type may affect dogs at any age, but is more common in dogs more than 8 years old. They may develop anywhere on the body as well as in internal organs. Many breeds appear to be predisposed, especially Boxers, Pugs, Rhodesian Ridgebacks, and Boston Terriers. These tumors may appear in multiple areas of the body at once and appear as raised, nodular masses that may be soft or solid upon touch. The tumors may vary widely in size, and clinical appearance alone cannot establish a diagnosis. Clinical signs of illness may appear in affected dogs; such as gastrointestinal problems. Diagnosis of these tumors can be difficult, yet cytology seems to be the number one choice if cancer is suspected. Treatments include wide, deep extraction of the tumor and surrounding tissues, followed by radiation therapy which may be curative if remaining tumor is small.

Basal Cell Carcinomas

They are more frequently recognized in cats than in dogs, developing more frequently in aged animals. Persians are predisposed. The tumor is often observed as ulcerated plaques on the head, extremities, or neck. They generally show some sort of continuity with the epidermis, they can be locally invasive, and appear in multiple areas of the body. Local or systemic metastasis rarely occurs for this type of cancer. Treatment of choice is surgical removal of the tumor. In dogs, most basal cell carcinomas show evidence of cornification, for this reason they can also be called basosquamous cell carcinomas. These tumors are generally recognized in older dogs, and several breeds are more susceptible, such as Saint Bernards, Scottish Terriers, and Norwegian Elkhounds. Unlike canine basal cell tumors, basosquamous cell carcinomas do not have a tendency to develop on the head and can be found almost anywhere on the body where they have continuity with the epidermis and appear nodules or plaques. These tumors are locally invasive but seldom metastasize.

Some specific types of pet cancer: Lymphoma, Osteosarcoma and Melanoma

Pet Lymphoma

This is one of the most common cancers seen in dogs and probably occurring 2 to 5 times as frequently in dogs than in people. This type of cancer can affect any dog at any age, though some breeds have a greater disposition for the disease. In many cases lymphoma first appears as swollen glands that can be seen or felt under the neck, in front of the shoulders, or behind the knee. In some cases lymph nodes inside the chest or abdomen may swell causing breathing problems or digestive problems. Multi-agent chemotherapy is the standard of care for this type of cancer. However, some more aggressive types of lymphoma may be nonresponsive to any available treatment.

Pet Osteosarcoma

This type of cancer is a very common type of bone cancer in the dogs, accounting for up to 85% of tumors that originate in the skeletal system. Although it is a disease more commonly seen in older giant breed dogs, it can affect dogs of any size or breed. The first signs of this disease may be lameness in the affected leg. Swelling over the area affected with the tumor or pain at the site may also be observed. This type of tumor tends to be very aggressive and metastatic, often finding the disease has already spread at the time of diagnosis. Standard of care for bone cancer normally includes removal of the primary tumor, followed by chemotherapy to attack the cells that have left the site.

Pet Melanoma

This type of disease is more commonly seen in dogs with dark pigmented skin; however, any dog can be affected by this type of tumor, which has its origins in the cells responsible for the coloring of the skin. These tumors have also been known to hold a hereditary component. Melanomas can form in areas of haired skin, where they may form small dark lumps, but can also be seen as large, flat, wrinkled masses. Melanomas can be both benign and malignant tumors, with the malignant tumors being incurable. These tumors tend to metastasize very quickly and the initial examination may show that the tumor has already spread, which makes complete surgical removal impossible. Radiation therapy often helps extend the life of the patient, but it is typically ineffective against metastasized cells. Chemotherapy is also used to control canine malignant melanoma. This disease seems to be uniquely responsive to immune-based therapies, and various novel approaches are under development.
There is currently a peptide vaccine in stage III clinical trials for metastatic melanoma. A peptide is a small portion of protein present in the surface of melanoma cancer cells, the vaccine works by stimulating the patient’s immune response to recognize the protein and destroy the tumor cells. The vaccine is often given in combination with other agents that activate the immune system.