Today's Veterinary Practice

NOV-DEC 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 42 NOVEMBER/DECEMBER 2018 Other primary intraocular neoplasms are uncommon in cats, but as in dogs, intraocular disease can be metastatic. Diagnosis and Prognosis Feline diffuse iris melanosis begins as benign, flat, hyperpigmented nevi on the iris. Over months to years, diffuse melanosis may progress to malignancy and should be monitored closely for changes. Photographs of the affected eye can help you evaluate these eyes over time. Melanoma lesions are distinguished by the spread of pigment, thickening of the iris, or irregular iris surface ( FIGURE 5 ). Eventually, these changes can invade the ciliary body, iridocorneal angle, and sclera, and may result in secondary glaucoma. 4,19–21 Rates of metastasis range from 55% to 66% after the lesions have become malignant, and the overall prognosis is poorer if the tumor has invaded the ciliary body or sclera at the time of enucleation. 1,3,7,12 The prognosis is also worse for cats that have secondary glaucoma. Posttraumatic ocular sarcomas in cats are highly malignant; these tumors should be suspected in cats with a history of trauma to the globe and evidence of uveitis, glaucoma, intraocular hemorrhage, and visible masses. For cats in which intraocular evaluation is inhibited by anterior segment opacity, ocular ultrasonography can facilitate characterization of the intraocular disease and its extent. The prognosis is poorer if the tumor has invaded beyond the sclera because it can involve the optic nerve and invade the brain; most of these cats die or are euthanized within months because of metastatic disease. 14 Iridociliary epithelial adenomas and adenocarcinomas in cats are generally solid and nonpigmented, as they are in dogs, and they are often accompanied by secondary complications, including retinal detachment and glaucoma. Although the prognosis for the globe is poor, as with other intraocular neoplasms, the potential for metastasis is low. 4 With regard to metastatic disease, lymphoma is the most common offender and can appear as anterior uveitis, an intraocular mass, or both. As previously discussed, bilateral ocular disease is suggestive of metastatic neoplasia. Cats with signs of metastatic intraocular neoplasia should also be tested for FeLV and FIV, both of which can predispose the cat to systemic neoplasia and thus intraocular metastasis. Treatment is systemic therapy, such as for lymphoma, as well as topical management of uveitis and secondary glaucoma, if present. Intraocular metastatic neoplasia can be difficult to distinguish from other causes of feline uveitis (e.g., feline infectious peritonitis, toxoplasmosis, or other infectious causes). Signalment and other systemic signs can help you determine the underlying cause, but any cat with profound bilateral uveitis should be evaluated for evidence of neoplasia in addition to infectious diseases. Treatment Enucleation is the treatment of choice for feline diffuse iris melanoma; however, for many patients, it is difficult to decide when to enucleate because of the slow disease progression as well as reluctance to remove a comfortable, visual eye. Close monitoring of these patients over time is imperative; look for significant changes of the pigmented areas, which may indicate the need for surgical intervention. Alternative techniques (e.g., diode laser ablation or sector iridectomy) have not been FIGURE 5. Photograph of the iris of a cat, showing flat, pigmented nevi (iris melanosis), which have not progressed to melanoma. Courtesy of Dr. Ellen Belknap Because of the high rate of malignancy of posttraumatic ocular sarcomas in cats, any blind eye that resulted from trauma should be considered for early enucleation.

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