Adenocarcinoma of the lung causing ectopic adrenocorticotropic hormone syndrome.

A patient with a left lower lung mass had muscle weakness, generalized hyperpigmentation, metabolic alkalosis, and profound hypokalemia. His elevated serum cortisol, corticosterone, and adrenocorticotropic hormone (ACTH) concentrations were not suppressed after midnight dexamethasone administration. Light and electron microscopic sections of the lung mass fitted the pathological criteria for adenocarcinoma. Immunocytochemical analysis of the tumor demonstrated specific staining with antibody to beta-endorphin, suggesting that the tumor cells made the common precursor molecule of ACTH, beta-lipotropin, and endorphin. This is, to the best of our knowledge, only the second case report of pulmonary adenocarcinoma associated with the syndrome of ectopic ACTH.