The role of integrated (18)F-FDG PET/CT in identification of ectopic ACTH secretion tumors.

The role of (18)F-Flurodeoxyglucose positron emission tomography ((18)F-FDG PET) scan in localization of ectopic Cushing's syndrome (EAS) tumor is still controversial. Here, we report on the use of integrated (18)F-FDG PET and computed tomography ((18)F-FDG PET/CT) in localization of EAS tumors in patients with ectopic Cushing's syndrome. Five patients, three men and two women, were reported, whose endocrine investigations and negative pituitary imaging were suggestive of ectopic ACTH secretion. (18)F-FDG PET/CT was performed to identify the source of ACTH secretion. Then the patients were suggested to perform pathologic examination. It turned out that all of these five patients have abnormal markedly intense FDG uptake lesions on (18)F-FDG PET/CT images. Four of them underwent lesion resection, whose plasma ACTH and serum cortisol levels returned to normal after the surgery. Also, they were at last remission from all the symptoms. Pathologic results showed one thymic carcinoid, one pulmonary carcinoid, one thymoma, and one pulmonary carcinoid with upper mediastinum carcinoid. Unfortunately, one patient died due to severe infection and electrolyte disorders. (18)F-FDG PET/CT technology integrates PET and CT imaging in one device so as to increase the accuracy of tumor localization and further improve the prognosis of the patients by curative resection.