Primary thymic carcinoid with Cushing's syndrome

Summary In a 52-year-old Caucasian man osteopoikilosis had been misdiagnosed roentgenologically 2 years before his death. Gradually he developed Cushing's syndrome and ultimately superior vena caval obstruction. At autopsy a primary thymic carcinoid with extensive osteoblastic bone metastasis was found. Immunohistochemically the tumor was shown to be positive for adrenocorticotropic hormone (ACTH), cytokeratin (KL1), neuron-specific enolase, synaptophysin, chromogranin and glucagon. Remarkably the tumour was negative for serotonin despite high urinary hydroxyindolacetic acid levels. Bilateral hyperplasia of the adrenal cortex was found. The adenohypophysis showed a considerable reduction of ACTH-producing cells and numerous Crooke's cells with a characteristic immunohistochemical pattern.