Recognition and Management of Ectopic ACTH Secreting Tumors

Ectopic ACTH syndrome (EAS), in which Cushing syndrome is caused by excessive ACTH secretion from a tumor located outside of the pituitary, is associated with an impaired quality of life and an increased mortality rate. Outcomes can be improved with successful tumor localization and resection, which often proves difficult. In order to distinguish EAS from Cushing disease, a significantly more common condition where excessive ACTH is secreted from a pituitary tumor, bilateral inferior petrosal sinus sampling (IPSS) is often necessary. Correct performance and interpretation of IPSS hence becomes crucial to avoid inappropriate future interventions, including surgical procedures. Once an ectopic source of ACTH is confirmed biochemically, identifying the causative tumor is often challenging since they can be located in unexpected areas and potentially be very small. Additionally, EAS carries a risk of severe hypercortisolism, which sometimes needs urgent treatment to avoid disastrous outcomes. The cases here illustrate pitfalls in diagnostic biochemical testing, describe helpful imaging strategies to improve the chances of tumor detection, and review available options to rapidly normalize severe hypercortisolism in critical situations.