Library
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Mast cells are a type of white blood cell that plays a large role in allergic response through degranulation. Mast cell tumors (MCT) can occur in the skin, spleen, or gastrointestinal tract of cats. Their cause is unknown; however, many affected cats show a genetic mutation in the KIT protein involved in replication and cell division. Cutaneous MCTs most often appear as hard pale/white plaques or nodules, often around the head and they may be itchy. Splenic MCTs cause decreased appetite, weight loss, and vomiting. Intestinal MCTs may cause GI upset and bloody stools, and a mass may be palpable. Diagnosis is typically achieved via fine needle aspirate although histopathology can be used. Treatment usually requires surgical removal of the masses or the spleen. Sometimes, chemotherapy or radiation is needed.
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Mast cell tumors are most common in the skin of dogs and may appear red, ulcerated, or swollen. They can be itchy and can fluctuate in size. Tumors can range from lower-grade, with minimal spread, to higher-grade, with a high risk of local invasion. Treatment usually involves surgical removal and may require supportive treatment including chemotherapy, radiation therapy, and therapy to target the mutation that instigated the tumor.
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Melanomas are cancerous growths of the cells responsible for pigmentation of the skin. They can develop anywhere on the body but those on the toes carry the highest chance for malignancy. They may be painful and you may notice your pet licking at the affected area. Surgery is often the treatment of choice and may be followed up with radiation or chemotherapy.
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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.
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Nasal tumors are an uncommon type of cancer but when they do occur, they tend to be malignant and locally aggressive. Staging can be done to determine the type of cancer and if it has affected anywhere else in the body. Treatment can be done in some cases to help relieve clinical signs, most often with radiation therapy.
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Neuroendocrine tumors are a group of tumors that develop from the cells of the neuroendocrine system, and include insulinomas, gastrinomas, glucagonomas, carcinoids, medullary thyroid carcinomas, small-cell lung carcinomas, pheochromocytomas, chemodectomas, and Merkel cell carcinomas. Some of these tumors are functional, while others are non-functional. The signs of disease in dogs and cats depend on the type of growth, location of the tumor, its size, the degree of infiltration in the surrounding tissues, whether it has metastasized, and whether it is functional. A definitive diagnosis requires tissue biopsy and histopathology, often with histochemical staining and electron microscopy. Staging is highly recommended for these tumors. Treatment may involve surgery, chemotherapy, radiation therapy, and medical and dietary management.
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Odontogenic fibromas, sometimes previously referred to as an epulis, are benign tumors of the mouth often at the front of the upper jaw. These may be locally invasive and may cause some oral pain. Surgery is the recommended course of action to treat this condition.
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Oral squamous cell carcinomas (SCC) are the most common oral tumor in cats, and second most common in dogs. These tumors are locally aggressive, with a possibility to metastasize. Regardless of the location of SCC, surgery is the typically the standard treatment. Radiation therapy may be recommended following surgery or as a primary treatment for palliative care. Staging is recommended for all cases. If metastasis is present chemotherapy is often pursued.
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Fibrosarcomas are the second most common oral tumor in cats and arise from the fibrous and connective tissues of the oral cavity. These tumors are very invasive locally and are often difficult to manage, Diagnosis is based on biopsy and treatment involves surgery and occasionally radiation or chemotherapy. Palliative care with pain relief and antibiotics are essential to improve quality of life.
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The most common oral tumor seen in cats is squamous cell carcinoma; the second most common is fibrosarcoma. This handout discusses the clinical signs, diagnosis and treatment of oral tumors in cats.