[Thymic carcinoid tumor revealed by a Cushing's syndrome: usefulness of positron emission tomography]

Ectopic adrenocorticotropic (ACTH) syndrome is a rare condition, generally due to lung or carcinoid tumors. 18-fluorodeoxy-glucose positron emission tomography ((18)FDG-PET) can be useful where conventional localization techniques often fail. A 50-year-old man presented with sudden diffuse oedema, hypokaliemic alkalosis, Diabetes mellitus and high serum levels of ACTH and cortisol. Ectopic ACTH syndrome was confirmed leading to ketoconazole treatment. Chest-computed tomography only revealed an aspecific anterior mediastinal nodule that was hypermetabolic on the whole body-(18)FDG-PET. A thymic tumor was suspected and the patient had a thymectomy that revealed an atypical carcinoid tumor with pleural carcinosis. The postoperative course was favorable with clinical and biochemical remission of neoplastic Cushing's syndrome.