A 61-year-old woman visited her primary care doctor because of general malaise, face edema, skin pigmentation, insomnia, and polyuria. Blood examination revealed marked hypokalemia and impaired glucose tolerance. Bilateral adrenal enlargement was observed on abdominal ultrasonography, and she was referred to our hospital for further examination. Endocrine examination showed both elevated plasma cortisol (107.7 pg/mL) and ACTH levels (1100 pg/mL), and increased urinary excretion of free cortisol (6650 mcg/day) and 17-ketogenic steroids (78.7 mg/day). Plasma cortisol and ACTH levels were elevated without any diurnal rhythm. Plasma cortisol was not suppressed by the overnight 8-mg dexamethasone suppression test. There was no response of plasma ACTH or cortisol to exogenous corticotropin-releasing hormone (CRH). Other hormones of the pituitary, thyroid, and adrenal medulla were all in normal ranges. Thus, ectopic ACTH syndrome was strongly suggested.
Chest computed tomography (CT) demonstrated a tumor of approximately 30 mm in diameter and enlargement of the lymph node in the anterior mediastinum (Fig. 1). High accumulation of 18-fluorodeoxyglucose in the anterior mediastinum tumor (maximum standardized uptake value [SUV] 2.48) but not in the lymph node was observed on positron emission tomography (PET)/CT. Somatostatin receptor scintigraphy also revealed mild uptake in the tumor. Collectively, these data were consistent with a diagnosis of EAS caused by an anterior mediastinum tumor, possibly thymic carcinoid tumor. There was no abnormal finding indicating multiple endocrine neoplasia (MEN).
Before the operation, we administered 500 mg/day of metyrapone, and both ACTH and cortisol levels decreased to 68.5 pg/mL and 3.02 mcg/mL respectively. After 2 months of medical treatment, her symptoms were relieved and bilateral adrenal enlargement decreased. Under open thoracotomy by median sternotomy, she underwent total thymectomy, pericardial partial resection, dissection of the anterior regional and the right paratracheal lymph nodes, and sampling of the subcarinal lymph node. Histopathologically, the tumor consisted of round to spindle-shaped cells with high nucleus/cytoplasm ratios containing finely granular chromatin. Necrosis was absent, and mitotic figures were infrequent, with less than two per ten high-power fields (HPF). Tumor cells were positive for chromogranin A, synaptophysin, CD-56, and ACTH on immunohistochemistry (Fig. 2). The tumor had invaded the pericardium, and mediastinal lymph nodes were positive for metastasis. The final diagnosis was stage IVA (pT2N1M0) ACTH-producing thymic typical carcinoid tumor. The plasma ACTH level decreased to 14.8 pg/mL, less than normal, immediately after surgery (Fig. 3). Hydrocortisone was administered during the perioperative period and was gradually tapered, and finished 4 months after surgery. She received postoperative radiation therapy of 60 Gy. At 8 months after surgery, she showed no sign of Cushing’s syndrome or recurrence of the tumor without any medications.