An unusual case of ectopic ACTH syndrome due to primary retroperitoneal carcinoid.

A 37-year-old woman with clinical and biochemical features of ectopic adrenocorticotropic hormone (ACTH) syndrome underwent 68Ga DOTANOC PET/CT to localize the source of ectopic ACTH secretion. The images showed 35 × 45-mm retroperitoneal mass with significantly increased tracer uptake. Plasma-free metanephrines and serum chromogranin levels were normal. Whole-body 131I-MIBG scan including the retroperitoneal mass did not show any abnormal uptake. On excision, histopathology of this paravertebral abdominal mass revealed carcinoid tumor. We suggest the use of 68Ga DOTANOC PET/CT as a first-line imaging modality for localization of source of ACTH secretion in ectopic ACTH syndrome.