engleski

Pheochromocytoma in an Arabian horse

Pheochromocytomas are predominantly benign, rare tumors in horses, that originate from chromaffin cells of the adrenal medulla. A small proportion of these may be functional and secrete catecholamines. A 20-year-old Arabian horse was presented with colon obstipation with consequent depression, exercise intolerance, and loss of appetite. Likewise, the horse had a clinical history of aortic regurgitation. Due to the unfavorable prognosis, the animal was euthanized. Post mortem examination revealed a large, well- demarcated right adrenal gland mass. Other necropsy findings revealed impaction of large colon with dry and hard content, eccentric left ventricular hypertrophy, subaortic endocardial jet lesions, endocardial hemorrhages and mild pulmo¬nary edema. Adrenal mass was submitted for histopathology. Microscopically, small polygonal cells formed nests and cords supported by a fine stroma and a large number of vascular sinuses. Tumor cells had round to oval nuclei, finely granulated chromatin and eosinophilic, granular, moderate cytoplasm. Cell pleomorphism was minimal and mitotic figures were infrequent. IHC revealed high expression of S-100 and NSE (neuron-specific enolase) antibodies. Histological and immunohistochemical findings were consistent with pheochromocytoma. Although most pheochromocytomas are non-functional and often accidental post- mortem findings, they should be considered in horses that exhibit symptoms associated with catecholamine increase.

adrenal gland ; pheochromocytoma ; horse

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