Surgical management of ectopic Cushing's syndrome from a pulmonary carcinoid secreting CRH supported by intraoperative ACTH monitoring - a case report.

An intraoperative ACTH monitoring during resection of hormone-secreting neuroendocrine neoplasms remains a subject of a debate. We present the case of a 36-year-old man with clinical and biochemical features of ACTH-dependent hypercortisolism. Dynamic endocrine testing, including the high-dose dexamethasone suppression test, metyrapone test, and desmopressin stimulation test resulted in inconclusive results, precluding clear differentiation between Cushing's disease and ectopic Cushing's syndrome. Pituitary imaging revealed no definite focal lesion, whereas chest imaging detected a small pulmonary nodule along with an incidental adrenal adenoma. Taking into account rapid clinical course and the severity of clinical symptoms surgical resection of the lung lesion was undertaken with intraoperative ACTH monitoring. Due to compilation of factors patient was sent to thoracic surgery without delay. A transient ACTH surge was observed during first stage tumor excision and, even though intraoperative pathological and surgical findings indicated the complete tumor resection, which contributed to the decision to extend the procedure to an upper lobectomy, after which a marked and sustained decline in ACTH concentrations was observed. Histopathological examination confirmed a typical pulmonary carcinoid tumor, and surgical treatment resulted in clinical and biochemical remission, followed by gradual recovery of the hypothalamic-pituitary-adrenal axis. This case highlights the limitations of dynamic testing and imaging in ECS, particularly in indolent presentation, and underscored the potential value of intraoperative ACTH monitoring as an adjunctive tool for tumor localization and surgical decision-making.