Educational Articles
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Chemotherapy is the therapeutic use of chemical agents to destroy or inhibit the growth and division of cancer cells. Usually, chemotherapy is used when tumors are widespread or when there is significant or immediate risk of spread from the primary location. It is often used following the surgical removal of tumors. In some cases, chemotherapy is started prior to surgery. The side effects of chemotherapy are related to the effects of chemotherapy on normal -as well as cancerous- cells. The principal goal of cancer care in pets is to provide cancer control without reducing quality of life.
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Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body such as the nasal cavity, and ribs. Chondrosarcoma is the second-most common primary bone tumor in dogs. Canine chondrosarcoma most commonly affects the flat bones of the body, such as the ribs, skull, nasal cavity, and pelvis, although the limbs can also be affected. Aggressive surgical removal is typically recommended, although radiation therapy may also be used, depending on location of tumor. Metastasis may occur but is relatively uncommon.
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Systemic lymphoma is a very common cancer in dogs, but the cutaneous form is quite rare. Current statistics suggest that cutaneous lymphoma accounts for only about 5% of canine lymphoma cases. The disease can present in a variety of lesions, including ulcers, nodules, red patches, and areas of hair loss and skin scaling. Because not very much is known about canine cutaneous lymphoma, there are no standard treatment protocols and the prognosis is poor.
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Collecting tissue samples for cytology or histopathology allow a pathologist to often give a diagnosis of the type of mass or tumor your pet has. Samples can be obtained by fine needle aspirate or biopsy, where a piece of the mass is cut out. Based on what the mass appears like under the microscope, the pathologist can often give a prognosis of how the tumor will behave.
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Esophageal tumors are extremely rare but more often than not malignant type tumors. The cause is unknown but cases in tropical environments may be due to infection by the worm Spirocerca lupi. Treatment options are limited as surgical complications are high due to the advanced nature of the disease at time of diagnosis.
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Hepatoid gland tumors are a type of cancer that develop from the sebaceous (sweat) glands of the skin. The most common location for these tumors to develop is the perianal area, and the most common tumor is the perianal adenoma. Perianal adenocarcinomas, and rarely perianal epitheliomas may also occur. These tumors appear as one or more small, round, pink, hairless, slow-growing nodules around the anus, and can sometimes ulcerate and become infected. Malignant tumors can grow much bigger and faster, invade the underlying tissue, and metastasize. Diagnosis may be made by fine needle aspiration, biopsy, or full excision of the tumor. Staging is recommended for adenocarcinomas. Treatment may involve surgical removal along with neutering, cryotherapy, laser ablation, radiotherapy, chemotherapy, and occasionally hormone therapy. The prognosis is good with perianal adenomas, fair to poor with adenocarcinomas, and generally good with epitheliomas.
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Infertility in a female dog is defined as the inability to conceive and deliver viable puppies, even when mated multiple times with a known fertile male surrounding the time of ovulation. This handout outlines the varying causes of infertility in female dogs and how they may be diagnosed and treated.
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Intestinal tumors are uncommon in dogs and cats, comprising about 2% of all cancers. There are many kinds, including leiomyosarcomas, lymphomas, adenocarcinomas, mast cell tumors, gastrointestinal stromal tumors (GISTs), plasmacytomas, carcinoids, and osteosarcomas (all malignant) and leiomyomas, adenomatous polyps, and adenomas (all benign). Most intestinal tumors are malignant. Intestinal tumors are more prevalent in older animals and certain breeds. Signs, diagnosis, and treatment are discussed.
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Lymphoma is a cancer of the lymph nodes and lymphatic system. This cancer may be localized to one particular region, or may spread throughout the entire body. Lymphoma is a relatively common cancer, accounting for 15-20% of new cancer diagnoses in dogs. The prognosis for lymphoma varies, depending on various characteristics that can only be determined by specialized testing.
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Many herding breeds (most commonly Collies and Australian Shepherds) have a mutation at the MDR1 gene that makes them more sensitive to the negative effects of certain medications. These drugs include several antiparasitic agents (when given at high doses), the antidiarrheal agent loperamide (Imodium®), and several anticancer drugs. The effects of the mutation vary in severity, depending on whether the dog carries one or two copies of the mutation. There is a cheek swab or a commercially-available test that assesses blood samples for the presence of the MDR1 mutation.