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 38 NOVEMBER/DECEMBER 2018 Melanocytic tumors can invade the choroid, sclera, filtration angle, cornea, and orbit. Distinguishing outward invasion of an iris melanoma from invasion of the iris by a limbal melanoma can be challenging. 3 The second most common location for primary intraocular tumors in dogs is the ciliary body. Tumors in this location are generally adenomas or adenocarcinomas. Rarely, they can be medulloepitheliomas (a type of neoplasia from undifferentiated epithelial cell types that can occur in younger dogs). Ciliary body adenomas and adenocarcinomas are usually found in older dogs and can sometimes be seen as a tan/pink mass extending through the pupil ( FIGURE 2 ). Labrador and golden retrievers may be predisposed to epithelial ciliary body tumors. 4 These tumors may also invade the iris, cause anterior displacement of the iris, or result in secondary uveitis and glaucoma. Often these masses are not diagnosed until they have caused secondary complications. Other primary ocular tumors have been reported in dogs but are extremely rare, and few have shown evidence of metastatic disease. One of these is schwannomas of blue-eyed dogs, a form of peripheral nerve sheath tumor. These tumors typically arise in the iris and ciliary body but are not common. 5 Metastatic Neoplasia Secondary, metastatic neoplasia in the eye can result from hematogenous spread and is most commonly seen with lymphoma or local invasion from adjacent structures. One study reported that 14.8% of all intraocular tumors in dogs were metastatic disease and that 6.3% of metastases were from lymphoma. 6 Reportedly, a wide variety of tumors metastasize to the eye: histiocytic sarcoma, mammary adenocarcinoma, hemangiosarcoma, malignant melanoma, and osteosarcoma. 5 Because the metastatic potential of most primary intraocular neoplasms is low, the presence of disseminated disease generally indicates that the intraocular tumor is metastatic. Ocular manifestations may be the first signs noticed but further workup can reveal a primary tumor elsewhere. Primary intraocular neoplasms are generally unilateral, whereas bilateral disease suggests metastatic disease. Bilateral ocular neoplasia should prompt a complete workup to evaluate for primary neoplasia elsewhere in the body, which can often be life-threatening. For any patient with unexplained hyphema, the differential diagnosis should include neoplasia, and ocular ultrasonography may help identify the presence FIGURE 1. (A) Uveal cyst. (B) Uveal melanocytic tumor in the dorsal iris of a dog. Note that both are darkly pigmented, but the cyst was freely movable during examination and easily transilluminated. B A FIGURE 2. Red, vascularized mass originating posterior to the iris in the pupil of a dog. Histopathologic diagnosis was adenoma of the ciliary body. Courtesy of Dr. Ellen Belknap (3)

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