Chemotherapy is the therapeutic use of chemical agents to destroy, or inhibit the growth and division of cancer cells. Chemotherapy is usually 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. Different protocols are used depending on the drug and the type of cancer being treated. The side effects of chemotherapy are related to the effects of chemotherapy on normal – as well as cancerous – cells. The principal goal with cancer care in pets is to provide cancer control without reducing quality of life. With pets, chemotherapy protocols are purposefully designed so the treatment does not become worse than the disease.
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, ribs, etc.). Chondrosarcoma is a rare tumor in cats, but it can occur. The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Clinical signs of chondrosarcoma may vary significantly, depending upon where the tumor arises. Although the mass may grow rapidly, less than 20% of feline chondrosarcoma cases metastasize to other parts of the body. Therefore, surgical removal is curative in many cases.
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, ribs, etc.). 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 resection is typically recommended, although radiation therapy may also be used (depending on location). Metastasis may occur, but is relatively uncommon.
Skin cancers are fairly common in cats, but cutaneous lymphoma is quite uncommon. Only about 3% of lymphoma cases in cats occur in the skin. There may be a linkage between feline leukemia virus (FeLV) and feline cutaneous lymphoma. Unfortunately, feline cutaneous lymphoma is considered incurable.
Systemic lymphoma is a very common cancer in dogs, but the cutaneous form is actually quite rare. Current statistics suggest that cutaneous lymphoma accounts for only about 5% of canine lymphoma cases.
Cytology is the microscopic examination of cell samples. Cytology can be used to diagnose growths or masses found on the surface of the body, and also to assess bodily fluids, internal organs, and abnormal fluids that may accumulate, especially in the chest and abdomen. Cells can be collected using various methods including fine needle aspiration, skin scraping, impression smear, cotton-tipped swabs, or lavage. A biopsy is the surgical removal of a representative sample of tissue from a suspicious lesion. The most common biopsy techniques are punch biopsy, wedge biopsy, and excision biopsy. The tissue is then processed and is examined under a microscope via histopathology. Histopathology allows the veterinary pathologist to make a diagnosis, classify the tumor, and predict the course of the disease.
Common conditions of pet rabbits include upper respiratory tract infections, internal and external parasites, dental disease, GI stasis, uterine problems, and pododermatitis. Upper respiratory infections are often caused by bacteria including Pasteurella multocida. Rabbits can become infected with various intestinal parasites, as well as external parasites such as ear and fur mites, fleas, and occasionally ticks. Rabbits’ teeth are continuously growing but chewing food, as well as chewing on wooden blocks, branches, and toys, helps them wear their teeth down at a rate equal to their growth. Occasionally, tooth or jaw trauma or disease causes misalignment of the upper and lower jaws and overgrowth of teeth results. Regular yearly check-ups enables early diagnosis and treatment of some rabbit diseases. Whenever a rabbit stops eating, for whatever reason, it is important to take her to see your veterinarian immediately for an evaluation.
Common conditions of pet rodents include respiratory diseases, gastrointestinal problems, dental problems, and tumors. Signs of respiratory disease in rodents include nasal and/or ocular discharge in mild infections, and wheezing, coughing, and open-mouth breathing in severe infections. Gastrointestinal disease, including diarrhea from various causes and gastrointestinal stasis is common in pet rodents. All rodents have teeth that grow continuously throughout their lives. Occasionally, these teeth grow too long and cut into the gums, causing pain, or prevent the mouth from closing properly, which often makes the pet stop eating. Just as in people, cancer is often seen in pet rodents, especially mammary (breast) tumors in rats and mice. Rodents with signs of respiratory or GI disease or evidence of a tumor should be seen by a veterinarian who can properly diagnose and treat the underlying condition.
Mast cell tumors are the most common skin tumor found in ferrets. They can also be found internally on the spleen. They arise from a cell type called a mast cell. In dogs and less so in cats, these tumors can vary from benign to highly malignant.
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.