Malignant canine anterior uveal melanoma.

Abstract

ported cases that demonstrate evidence of metastasi~.~~~.~ ~~.~~ An example of primary intraocular melanoma of the anterior uvea with cardiac and pulmonary metastases is discussed. The classification of canine ocular melanomas is controversial and incon~istent.~-~ ,~,~-~~ A simplified system, which divides the anterior uveal melanomas in adult dogs into benign and malignant groups based on cellular anaplasia, would facilitate accurate reporting. A 10-year-old, ovariohysterectomized, female German Shepherd Dog was presented with a 4-week history of an inflamed right eye unresponsive to treatment with topical antibiotics. Three weeks earlier, the dog had experienced an episode of coughing, respiratory distress, and incontinence, which responded to amoxicillin and codeine cough medication. Benign mammary masses had been removed 5 years previously. Ophthalmic findings of the right eye included severe panuveitis and glaucoma, characterized by a buphthalmic globe, corneal edema, ciliary flush, hyphema, severe aqueous flare, hyperemic conjunctiva, swollen iris, and posterior synechia. The right fundus could not be seen. The left eye was normal. Intraocular pressures were 25 and 9 mm Hg in the right and left eyes, respectively, by applanation tonometry. The right eye was blind with no direct or consensual pupillary light response. Two mammary masses were palpated. Because the right eye was irreparably blind and painful, enucleation was recommended. Differential diagnosis included primary or metastatic neoplasia and systemic fungal disease. A thoracic radiograph revealed multiple masses within the lung. Malignant neoplasia was considered likely, and the dog was euthanatized. Pos mortem examination was performed immediately following death. Gross examination revealed a large (4 cm in diameter), raised, black lesion within the dorsal parenchyma of the left caudal lung lobe. Several smaller masses (0.4-2.5 cm in diameter) were found in this lobe as well as in other lobes. These masses varied in color from black, to dark red, to pink. One mass was found immediately adjacent to a bronchus that had erosions of the overlying mucosal epithelium. There was a dark-red pedunculated mass (1 cm in diameter) on the external surface of the right atrium (Fig. 1). Two mammary gland masses were found: one in the left caudal gland (2 cm in diameter) and one in the right inguinal region (3 cm in diameter), which contained multiple cysts. The mammary masses were diagnosed as benign, mixed-mammary tumors on histopathologic examination. A thorough examination of the oral cavity, skin, and digits revealed no abnormal masses. The right eye was removed, fixed in Bouin’s solution, and sectioned mid-sagitally. A proteinacous precipitation in all internal chambers of the eye made gross examination of the sectioned eye impossible. Histologically, in the plane of section, the upper and lower iris were symmetrically thickened and distorted by an infiltrative neoplastic mass. Neoplastic cells extended into the upper and lower ciliary body stroma causing destruction of the ciliary epithelium in at least one focus. Near the limbus, neoplastic cells had infiltrated the cornea anterior to Descemet’s membrane and aggregated in the anterior chamber on the posterior corneal surface. The peripheral cornea was edematous and vascularized. The posterior segment was relatively uninvolved. Overt intravascular infiltration of neoplastic cells was seen in the sclera. The tumor was composed of tightly packed clusters of