Small tumors producing adrenocorticophic hormone (ACTH) ectopically may be very difficult to locate. We describe a 57-year-old woman who presented with ectopic Cushing's syndrome as diagnosed by bilateral inferior petrosal sinus catheterization with corticotrophin-releasing hormone (CRH) test. Thoracic pentetreotide (a somatostatin analogue) revealed a small "hot spot" in the base of the left lung. This "hot spot" was constant throughout the procedure. A second thoracic CT scan with 3-mm cuts showed a small image in the area under suspicion, similar to vascular images found elsewhere in both lungs. At surgery, an 8-mm tumor was found and excised. Pathological examination revealed a carcinoid tumor immunoreactive for ACTH, beta-endorphin, bombesin, serotonin, and the α-subunit. One month after surgery, the patient was clinically well and had normal adrenal function. An111ln-pentetreotide scintiscan clearly identified a small ACTH-producing neuroendocrine tumor of the lung undetectable by plain chest radiography or CT scan.
Keywords: Bombesin; Carcinoid Tumor; Endocrine Pathology Volume; Inferior Petrosal Sinus; Pentetreotide.