Histologic, Immunohistochemical, and Ultrastructural Features of an Intraocular Sarcoma of a Cat

Abstract

There are numerous reports in the literature of feline intraocular neoplasms. Metastatic and secondary (hematopoietic tissue origin) tumors are described most commonly, and lymphosarcoma is most regularly mentioned. Primary intraocular neoplasms in cats are rare, with melanoma of the anterior uvea representing the most common type. Intraocular sarcomas other than melanomas are rare; osteosarcoma, chondrosarcoma, fibrosarcoma, and poorly differentiated spindle cell sarcomal have been described. Chronic uveitis or previous ocular trauma years before usually precede the sarcomas. 1,4 Most of the sarcomas had diffuse involvement of the eye with effacement of much of the normal architecture. All had various degrees of scleral invasion, with occasional extension into the orbit. Vascular invasion or metastasis occurred in some of the cases. These sarcomas were not described ultrastructurally. In this report, we present histologic and ultrastructural descriptions of an intraocular sarcoma in a cat. A 13-year-old castrated male domestic short hair cat was in apparent good health except for a 4-year history of intermittent uveitis and glaucoma of the right eye. The eye was treated with medications for uveitis and glaucoma, including intraocular injections of gentamicin. A recent examination of the eye revealed a mass in the posterior and vitreous chambers that protruded into the anterior chamber. The globe was enucleated and submitted for histologic examination. Gross examination of the formalin-fixed eyeball revealed a firm, tan, multilobulated 2.1x 1.5cm intraocular neoplasm in the vitreous and posterior and anterior chambers. The tumor appeared to arise in the nasal and inferior portions of the eye, incorporating the iris, ciliary body, and retina. Detached portions of retina floated free in the vitreous chamber. Horizontal sections of the eye were cut to ensure inclusion of the mass in the plane of section. Six-micrometer sections of the eye were stained with hematoxylin and eosin (HE) and phosphotungstic acid hematoxylin (PTAH). Additional sections were examined by an avidin-biotin complex (ABC) peroxidase technique for actin and myoglobin. A piece of the ocular mass was prepared for transmission electron microscopy. Histologically, the neoplasm invaded the cornea, iris, ciliary body, and sclera. Clumps of neoplastic cells were observed in emissary veins. Examination of the HEand PTAHstained tissue sections revealed pleomorphic cells arranged