SIGNS OF SYMPATHETIC DENERVATION ASSOCIATED WITH A THORACIC MELANOMA IN A HORSE

Sympathetic denervation in a 20-year-old, gray, Thoroughbred-Percheron gelding was manifested by cutaneous hyperthermia and sweating over th e right side of the body, demarcated by a line from the withers to the elbow and extending cranially. There was cutaneous hyperthermia over the right side of the head, but other signs of Horner's syndrome (swea ting, ptosis, miosis, enophthalmos) were not present. The pattern of c utaneous hyperthermia and sweating was consistent with sympathetic den ervation localized to the cervicothoracic ganglion, and thoracic radio graphs revealed increased density in the craniodorsal thorax. Cytologi c evaluation of a sample of pleural effusion revealed mesothelial cell s containing melanin and cells suggestive of melanocytes or melanoblas ts. Treatment with oral cimetidine and intrapleural cisplatin was not successful. A necropsy was not performed, but the clinical findings su pported a diagnosis of thoracic melanoma involving the cervicothoracic ganglion. Copyright (C) 1997 by the American College of Veterinary In ternal Medicine.