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Common conditions of pet rodents include respiratory diseases, gastrointestinal problems, dental problems, and cancer. Diseases of the skin may cause itching, hair loss or flaky skin in rodents. All rodents have teeth that grow continuously throughout their lives. Occasionally, these teeth grow too long and cut into the gums, causing pain when eating. 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.
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Ear canal tumors are abnormal growths that can develop from any part of the ear canal (the skin, the glands of the skin that produce earwax and oil, and the underlying connective tissues, muscles, and bones). Initially, these tumors may appear as one or more pink, white, or purple nodular masses in the ear canal. If benign, they may grow to a certain size and may or may not be problematic. If malignant, they may grow, ulcerate (break open) and bleed, and nearly always become infected, causing recurrent or chronic ear infections. The treatment of choice for ear canal tumors is surgical excision.
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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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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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Mast cell tumors are one of the most common skin tumors in ferrets. These tumors are typically a small, raised growth on the skin that erupts, may bleed, then heal only to reoccur several weeks later in the same location. Unlike mast cell tumors in dogs, mast cell tumors in ferrets do not spread to internal organs.
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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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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.