Abstract
BACKGROUND: Ectopic Cushing syndrome (ECS) is a sporadic condition. Even uncommon is an ECS that derives from a carcinoid tumor of the thymus. These tumors may pose several diagnostic and therapeutic conundrums. This report discusses the differential diagnosis, clinicopathological findings, and effective treatment of a rare case of ECS using a minimally invasive approach. CASE PRESENTATION: A 29-year-old woman with Cushing syndrome presented with facial flushing. Physical examination revealed hypertension (blood pressure: 141/100 mmHg). A mediastinal tumor was discovered to be the cause of the patient's chronic hypokalemia and hypercortisolemia. Cortisol levels increased in the morning, reaching 47.7 ug/dL. The levels of the hormones ACTH, aldosterone, and renin were determined to be 281 pg/mL, 3.0 ng/dL, and 2.1 pg/mL, respectively. The presence of hypertension, hypokalemia, and alkalinity suggested Cushing's syndrome, which was proven to be ACTH-dependent ECS by a dexamethasone suppression test. A chest CT scan revealed inflammation in the posterior basal region of the right lower lobe. The superior anterior mediastinum was characterized by round-shaped isodensity lesions with distinct borders. She underwent thoracoscopic anterior mediastinal tumor excision via the subxiphoid technique (R0 resection); following surgery, her blood pressure returned to normal, and the hypernatremia/hypopotassemia resolved. The tumor was determined to be a thymic carcinoid. Most notably, cortisol levels fell to half of their presurgical levels after one hour of surgery, and other abnormalities corrected substantially postoperatively. CONCLUSION: Thoracoscopic excision of thymic tumors by subxiphoid incision may be a useful treatment option for ECS caused by neuroendocrine tumors of the thymus.