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Abstract
Canine ocular nodular episcleritis (CONE) or nodular granulomatous episcleritis develops in the sclera, limboscleral junction and third eyelid and may infiltrate the cornea and its etiology is unknown. This condition is recurrent and inconsistently responds to surgery and immunomodulating medications. We characterized CONE histologically and for the first time immunohistochemically. Forty-two paraffin-embedded specimens obtained from UGA and COPLOW laboratories were stained with H&E and characterized histologically as inflammatory or proliferative. Tissues were stained with Massons trichrome, Reticulin, CD3, CD79, MAC387, TGF2, smooth muscle actin (SMA), and desmin. Twenty-three samples (54.5%) were characterized as inflammatory (predominant CD3+ and SMA) and 17(46.5%) as proliferative (predominant TGF2 and reticulin). CD3+ and TGF2 were predominant in both groups. The histiocytic-like cells seen in both lesions were non-immunoreactive for MAC387, those cells may be histiocytes in a different stage not expressing MAC387 or may cells from a different lineage.