MULTIPLE ENDOCRINE NEOPLASIAS IN A DOG - CORTICOTROPIC TUMOR, BILATERAL ADRENOCORTICAL TUMORS, AND PHEOCHROMOCYTOMA

In a 10-year-old ovariohysterectomized standard Schnauzer, the finding of dexamethasone-resistant hypersecretion of cortisol, the results of computed tomography, and elevated plasma concentrations of ACTH sugge sted the presence of both adrenocortical tumour and pituitary-dependen t hyperadrenocorticism. The dog made an uneventful recovery after bila teral adrenalectomy and remained in good health for 31/2 years with su bstitution for the induced hypoadrenocorticism. Then the enlarged pitu itary caused neurological signs and eventually euthanasia was performe d. The surgically excised right adrenal contained a well-circumscribed tumour of differentiated adrenocortical tissue and in the left adrena l there were two adrenocortical tumours and a pheochromocytoma. The un affected parts of the adrenal cortices were well developed and without regressive transformation, At necropsy there were no metastatic lesio ns, The cells of the pituitary tumour were immunopositive for ACTH and had characteristics of malignancy. The present combination of cortico trophic tumour, adrenocortical tumours, and pheochromocytoma may be ca lled 'multiple endocrine neoplasia' (MEN), but does not correspond to the inherited combinations of diseases known in humans as the MEN-1 an d the MEN-2 syndromes. It is suggested that the co-existence of hypera drenocorticism and pheochromocytoma may be related to the vascular sup ply of the adrenals, Some chromaffin cells of the adrenal medulla are directly exposed to cortical venous blood, and intra-adrenal cortisol is known to stimulate catecholamine synthesis and may promote adrenal medullary hyperplasia or neoplasia.