Educational Articles
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Eye melanomas in cats may be benign or malignant (cancerous). Malignant tumors, called diffuse iris melanomas, show up as multiple spots of color change in the iris, while benign tumors, called limbal melanomas, present as a distinct mass at the edge of the cornea. The diagnosis of these tumors is largely by clinical signs and tumor appearance. Treatment for diffuse iris melanomas may include close monitoring, laser surgery, removing part of the iris (iridectomy) and removing the eye (enucleation). Metastasis has been reported in about 19-70% of cases of diffuse iris melanoma, with most spread to the regional lymph nodes, kidneys, liver, and lungs. Treatment for limbal melanomas may include close monitoring, and surgery, sometimes combined with cryosurgery, laser surgery, or radiation therapy. Enucleation is an option if the treatment is unsuccessful, or the tumor regrows.
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Eye melanomas, although rare, are the most common eye tumor in dogs. These melanomas can originate from the uvea (structures in the front part of the eye) or the limbus (the part where the cornea and the white part of the eye meet). About 80% of uveal melanomas and all limbal melanomas are benign. The rate of metastasis (spread to other parts of the body) is less than 20%. Ocular melanomas are at least in part heritable and may caused by one or more genetic mutations. Uveal melanomas can become discrete, raised pigmented masses that damage the intraocular structures of the eye and cause hyphema (blood in the front part of the eye), uveitis (inflammation of the front part of the eye), and glaucoma (increased pressure in the eye). Limbal melanomas can invade the cornea and cause keratitis (inflamed cornea), grow outwards and cause conjunctivitis, and penetrate and damage the eye as with uveal tumors. Treatment for ocular melanomas may include close monitoring, surgery, iridectomy (removal of part of the iris), laser surgery, cryotherapy, radiation therapy, and enucleation (removing the eye), depending on the type and size of the tumor and how it is affecting the eye. The overall prognosis is good.
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Primary intraocular tumors, aside from melanoma, are relatively uncommon. There are many different types of primary tumors, including ciliary body adenoma and adenocarcinomas, uveal schwannomas of blue-eyed dogs, feline post-traumatic ocular sarcomas, and iridociliary adenomas and adenocarcinomas. When an intraocular tumor is suspected, a referral to a veterinary ophthalmologist may be recommended. Diagnosis is usually via an abnormal ophthalmic examination and/or ophthalmic ultrasound. Surgery is often recommended, especially if the pet has symptoms that reduce quality of life. The risk of metastasis is related to the type of tumor.
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Tumors can affect the eyelids, conjunctiva, and periocular tissues can be benign or malignant and can lead to secondary problems such as eye infections and corneal ulcerations. Diagnosis is best achieved through surgical excision of the tumor, but fine needle aspiration may be pursued as an initial diagnostic. Surgery is highly recommended to provide the pet with symptomatic relief, remove the tumor, and obtain a definitive diagnosis.
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Fibrosarcomas are a type of soft tissue cancer that is common in dogs. They are most often found on the limbs and trunk of the body but can also be found in the nasal cavity or mouth. They usually originate from the connective tissue of the skin and beneath the skin, but occasionally from the bone. Older dogs and certain breeds (especially large breeds) are at greater risk. Fibrosarcomas are often painful. Surgery is the treatment of choice for fibrosarcomas, with or without radiation and/or chemotherapy. With proper and prompt treatment, favorable outcomes are possible.
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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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Primary liver tumors in dogs and cats are rare. There are 4 types: hepatocellular tumors, bile duct tumors, neuroendocrine tumors, and sarcomas. These cancers can be massive, nodular, or diffuse in form. In dogs, most liver tumors are malignant, while in cats, most are benign. The signs of liver tumors range from being asymptomatic to having inappetence, fever, lethargy, and weight loss; and less commonly, nausea, vomiting and diarrhea; increased drinking and urination; and jaundice. Occasionally there are neurological signs, such as seizures. With tumor rupture and intrabdominal bleeding there may be weakness, collapse, and difficulty breathing. The diagnosis is based on history, clinical signs, exam findings, diagnostic imaging, and FNA or liver biopsy. A biopsy is best for a definitive diagnosis. Surgery is the treatment of choice for most primary liver tumors followed by chemotherapy. Chemoembolization is a newer treatment.
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Lung tumors are considered rare in cats and dogs. Many pets may not show symptoms at first, and a tumor may be found coincidentally. Depending on the type and stage of cancer, treatment may be possible; otherwise, symptomatic supportive care may be an alternative option.
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Lymphatic tumors are rare in pets. Lymphangiomas are benign and lymphangiosarcomas are malignant and have a moderate-to-high metastatic potential. Patients with lymphatic tumors typically have severe edema or cavity effusions because of lymphatic obstruction and leakage. These types of tumors occur more frequently in young dogs and cats. Treatment usually involves surgical excision and chemotherapy may be used as a follow-up treatment in the case of lymphangiosarcomas.
