Imaging strategies for localization of ACTH-secreting tumors

Abstract

The causes of ACTH-dependent Cushing’s syndrome include corticotrope tumors that secrete ACTH (Cushing’s disease) and tumors outside the pituitary gland that secrete ACTH “ectopically” (Ectopic ACTH secretion). Since pituitary tumors are much more common, imaging usually begins with a pituitary MRI. The specific protocol used for the study influences the ability to identify a tumor, but even the best protocols do not identify more than 80 % of these tumors. Ectopic ACTH-secreting tumors occur most commonly in the thorax but may be found in the neck, abdomen, or pelvis. Structural imaging with CT (and MRI as an adjunctive modality) is the mainstay but is complemented by function imaging, usually with somatostatin analogs. Since many tumors are occult at initial presentation, imaging is repeated at intervals until a tumor is identified and (hopefully) resected.