Tumors of the endocrine system in the horse - clinical pathology

Abstract

This paper presents the clinical pathology of 22 horses (0.5% of the 4359 horses necropsied) with tumors of the endocrine system necropsied in the Institute of Veterinary Pathology of the University of Leipzig from 1890 until 2008. Regarding horses with tumor diseases (n=87) 25.3% of them showed endocrine tumors. Especially older horses (mean age 17.6 years) were affected. Besides cases of an equine Cushing's disease (n=5) most patients (n=17) were clinically without any signs of endocrine disorders. In these cases the tumors were incidental findings during necropsy. In 23% (5 / 22) the simultaneous occurrence of several tumors in different endocrine tissues (thyroid, adrenal and pituitary gland) were documented. It should be discussed if such findings in horses reflect only a serendipitous coincidence of multiple tumors or rather represent an equine variant of the multiple endocrine neoplasia (MEN) syndrome in humans. In horses with an undefined unilateral mass in the cervical region the biopsy serves as an important diagnostic tool, but it is impossible to use the results for an individual prognostic assessment in cases of malignant thyroid tumors.