18 F-FDG PET/CT and 68 Ga-DOTA-NOC PET/MRI in an Adolescent With Ectopic Adrenocorticotropic Hormone Syndrome From a Presacral Teratoma.

A 13-year-old girl with severe Cushingoid features had ectopic ACTH-dependent Cushing syndrome. 18 F-FDG PET/CT demonstrated diffusely FDG-avid bilateral adrenal hyperplasia, confirming ectopic ACTH stimulation, and detected a presacral mass with mild uptake. 68 Ga-DOTA-NOC PET/MRI revealed intense somatostatin-receptor activity (SUVmax: 56.1), and MRI identified fat and cystic elements, suggesting teratoma. Surgery proved a mature teratoma harboring an ACTH-secreting NET (G1). This rare case demonstrates that in pediatric patients with aggressive-appearing presacral masses and life-threatening hypercortisolism, complementary imaging modalities may be necessary to exclude malignancy while identifying the functional tumor source.