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A cutaneous histiocytoma is a common benign (harmless) tumor of the skin in dogs, typically younger ones. Their development, appearance, diagnosis, and treatment are explained in this handout.
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Cutaneous histiocytosis is an uncommon condition in dogs. It is a non-cancerous increase in the number of reactive cells (histiocytes) caused by an immune system dysfunction. It generally manifests as multiple bumps and nodules confined to the dog's skin. The clinical signs, diagnosis, and treatment of this condition are explained in this handout.
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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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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, 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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There are a number of tumors that affect the eyelids, conjunctiva, and periocular tissues. These can be benign or malignant and can lead to secondary problems such as eye infections and corneal ulcerations. Diagnosis is best achieved through complete 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. With malignant tumors, surgery is the mainstay of therapy, though radiation therapy is sometimes pursued in cases where surgical removal is not possible.
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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.