Classification of feline intraocular neoplasms based on morphology, histochemical staining, and immunohistochemical labeling


  • Bruce H. Grahn,

    1. Departments of Small Animal Clinical Sciences and
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  • Robert L. Peiffer,

    1. Department of Ophthalmology and Pathology, School of Medicine, The University of North Carolina, CB 7040, 617 Clinical Sciences Building, Chapel Hill, NC 27599-7040, USA;
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  • Cheryl L. Cullen,

    1. Department of Companion Animals, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, C1A 4P3 Canada
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  • Deborah M. Haines

    1. Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, S7N 5B4 Canada;
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Address communications to: B. H. Grahn Tel.: (306) 966-7083 Fax: (306) 966-7129 e-mail:


The objectives of this study were to evaluate morphologic, histochemical, and immunohistochemical characteristics of well-differentiated and anaplastic intraocular neoplasms of cats, and to develop a diagnostic algorithm for, and investigate the association of ruptured lenses with these neoplasms. Seventy-five feline globes with intraocular neoplasms were stained with hematoxylin and eosin and examined by light microscopy. Morphologic diagnoses included 33 intraocular sarcomas, 17 diffuse iris melanomas, 15 lymphosarcomas, three ciliary adenomas, one metastatic carcinoma, and six undifferentiated intraocular neoplasms. Sections of these globes were then stained with periodic acid Schiff (PAS), and immunohistochemical (IHC) labels for various cellular markers. Histochemical staining and IHC labeling confirmed cellular differentiation in 73/75 neoplasms but was discordant with morphologic diagnoses in 8/75. These included four neoplasms morphologically diagnosed as lymphosarcomas but which expressed differentiation antigens consistent with melanoma (n = 3) or ciliary adenocarcinoma (n = 1), and four tumors morphologically diagnosed as intraocular sarcomas that expressed differentiation antigens for melanoma (n = 2), metastatic carcinoma (n = 1), or remained undifferentiated (n = 1). Immunohistochemical labeling suggested a diagnosis in 5/6 morphologically undifferentiated neoplasms including one intraocular sarcoma, two diffuse iridal melanomas, and two ciliary adenocarcinomas. Based upon morphologic, histochemical, and IHC characterization, ruptured lens capsules were detected in 28/30 intraocular sarcomas, 3/24 diffuse iris melanomas and 1/11 lymphosarcomas, but not in ciliary epithelial neoplasms, metastatic carcinomas, or undifferentiated intraocular neoplasms. An algorithm is provided that facilitates stain and IHC label selection for differentiating anaplastic intraocular feline neoplasms.