• This is an important differential diagnosis for adrenocorticotropic hormone (ACTH)-dependent Cushing’s syndrome. It has a more rapid and fulminant onset with significantly higher levels of ACTH, serum hypercortisolemia and urine free cortisol levels when compared with pituitary-dependent Cushing’s syndrome.
• Intrathoracic origin for ectopic ACTH-producing tumors is the most common; particularly thymic, bronchial carcinoid and bronchogenic carcinoma.
• Opportunistic infections which are secondary to immune suppression are more common and can be lethal if not treated aggressively.
• Thymomas are frequently malignant and clinical remission postoperatively is uncommon.

In patients with severe clinical symptoms of Cushing’s, control of hypercortisolemia with medical management, particularly ketoconazole, and in refractory cases, early adrenalectomy may precede the excision of the primary tumor.