ACTH-Secreting Pheochromocytoma with False-Negative ACTH Immunohistochemistry

Excerpt

Since 1955, when Roux [1] published the first association between pheochromocytoma and Cushing’s syndrome, we have come to appreciate the unique features of this unusual clinical entity. Pheochromocytoma represents a rare cause of hypercortisolism, accounting for less than 5 % of ectopic Cushing’s syndrome [2, 3] while less than 1 % of pheochromocytomas is accompanied by Cushing’s syndrome [4]. Pheochromocytomas are known to be heterogeneous, both functionally and clinically, a likely consequence of their ability to synthesize and secrete peptides in addition to catecholamine, such as vasoactive intestinal polypeptide, somatostatin, and calcitonin [5]. As regards hypothalamo–pituitary–adrenal axis peptides, both adrenocorticotropin (ACTH) and other proopiomelanocortin (POMC)-derived peptides [6, 7] as well as, occasionally, corticotropin-releasing hormone (CRH) [8] have been demonstrated in pheochromocytomas associated with ectopic Cushing’s syndrome. …